MQX-Enabled MCF51EM256 SinglePhase Electricity Meter Reference
Design
Using the MCF51EM256, MC1322x and MMA7660FC
Document Number: DRM121
Rev. 0
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Contents
Section Number
Title
Page
Chapter 1
Introduction
1.1 Overview..........................................................................................................................................................................7
1.2 General platform features.................................................................................................................................................8
1.2.1 Hardware design features .....................................................................................................................................8
1.2.2 Software features of the design..............................................................................................................................9
1.3 MCF51EM256 Microcontroller series.............................................................................................................................9
1.3.1 Peripheral application usage..................................................................................................................................11
1.4 1322x low power node (LPN)..........................................................................................................................................13
1.5 MMA7660FC 3-axis Xtrinsic accelerometer...................................................................................................................15
Chapter 2
Basic Theory
2.1 Definition of terms...........................................................................................................................................................17
2.1.1 Power.....................................................................................................................................................................17
2.1.2 Energy....................................................................................................................................................................19
2.1.3 Power factor...........................................................................................................................................................19
2.2 Electricity distribution......................................................................................................................................................20
2.3 Electricity meters..............................................................................................................................................................21
2.3.1 Electromechanical meters......................................................................................................................................22
2.3.2 Electronic meters...................................................................................................................................................22
2.4 Voltage and current measurement....................................................................................................................................24
2.4.1 Voltage divider......................................................................................................................................................25
2.4.2 Shunt resistor.........................................................................................................................................................26
2.4.3 Current transformer...............................................................................................................................................26
2.4.4 Rogowski coil........................................................................................................................................................28
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Section Number
Title
Page
Chapter 3
System Concept
3.1 Application description....................................................................................................................................................29
3.1.1 Metering board.......................................................................................................................................................30
3.1.2 Switch mode power supply board connection.......................................................................................................33
3.1.3 External current sensors connection......................................................................................................................34
3.1.4 1322x-LPN connection..........................................................................................................................................35
3.1.5 Power meter case...................................................................................................................................................36
3.2 Application usage.............................................................................................................................................................38
3.2.1 Power meter hardware configuration.....................................................................................................................38
3.2.2 Application example..............................................................................................................................................39
Chapter 4
Hardware Design of the Metering Board
4.1 Introduction to hardware implementation........................................................................................................................41
4.2 Power supply ...................................................................................................................................................................41
4.3 Digital hardware ..............................................................................................................................................................42
4.3.1 MCU core..............................................................................................................................................................42
4.3.2 RS232 interface.....................................................................................................................................................43
4.3.3 Infrared interface (IEC1107).................................................................................................................................44
4.3.4 User interfaces.......................................................................................................................................................44
4.3.5 LED interface.........................................................................................................................................................45
4.3.6 SPI interface...........................................................................................................................................................45
4.3.7 Accelerometer interface.........................................................................................................................................45
4.3.8 IIC interface...........................................................................................................................................................46
4.4 Signal conditioning ..........................................................................................................................................................47
4.4.1 Voltage measurement............................................................................................................................................50
4.4.2 DC Bias circuit......................................................................................................................................................50
4.4.3 Shunt resistor current measurement.......................................................................................................................51
4.4.4 CT current measurement........................................................................................................................................53
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Section Number
Title
Page
4.4.5 Input protection......................................................................................................................................................55
Chapter 5
Application Set-Up
5.1 Setting-up the demo hardware .........................................................................................................................................57
5.2 Setting-up the software demo...........................................................................................................................................58
5.2.1 FreeMASTER data visualization ..........................................................................................................................58
5.2.2 ZigBee communication .........................................................................................................................................60
5.2.3 Code reprogramming via serial bootloader...........................................................................................................63
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Chapter 1
Introduction
1.1 Overview
This design reference manual describes the solution for a single phase electricity meter
based on the MCF51EM256 microcontroller (MCU). The design demonstrates the
capabilities of this MCU for electricity metering applications. There are also additional
Freescale components used in this design, including the RF (ZigBee) and accelerometer
solution (interface).
The reference design provides a high performance solution for power measurement in
single phase two-wire installations. The target market is residential metering. The
reference design has the ability to connect to a ZigBee® network thanks to the integrated
1322x low power node, hence it can easily become part of the smart grid network.
Besides this development, this design uses the MQX real time operating system, to
improve the code structure and to serve as a proof of concept for the true real-time
applications, such as a power meter. Because of the MQX, this power meter is designed
for use in advanced markets.
In addition, various analog front end configurations and measurement methods are
explored, implemented, and compared in this reference design. This reference design
manual describes only the hardware solution for the power meter. Software solutions;
mainly metering algorithms are described in associated documents, like the application
note titled FFT-based Algorithm for Metering (document AN4255).
The power meter reference design is prepared for use in a real customer metering area,
this is due to the implemented HMI (LCD and buttons) and communication interfaces for
remote data collecting (AMR). Finally, it provides both hardware and software solutions
for customer applications.
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General platform features
1.2 General platform features
This chapter describes the main hardware and software features of the MCF51EM256
Power Meter Reference Design.
1.2.1 Hardware design features
• 5 (100) A current range, nominal current is 5 A, peak current is 100 A
• 120/230 V AC, 50/60 Hz operational range
• Accurate metering function (IEC50470-3 class B), 1% (applicable for two-gain
stages configuration)
• Active and reactive power (energy) measurement
• Line frequency measurement (for precision zero-cross detection)
• Two standard current sensing circuit implementations (shunt resistor and CT)
• Voltage sensing is executed by an inexpensive resistor divider
• Cost-effective bill of materials (BOM) due to various configurations of hardware
signal conditioning parts
• Low-power modes effectively implemented, including the use of standby RAM and
RTC
• 3 V internal battery for proper RTC function and data storage for a minimum 10
years
• 4 x 40 segment LCD, including charge pump (values shown on the LCD:
V,A,W,Var,VA,kWh, kVArh, cos , Hz, time, date)
• Tamper detection via:
• Built-in tamper push-button
• 3-axis IIC MMA7660FC accelerometer (optional only)
• Simple user interface — Two user buttons, one LED
• LED pulse outputs (kWh,kVArh)
• Open-collector power pulse output — Maximum power rating is 1.6 W
• IEC1107 infrared hardware interface
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Chapter 1 Introduction
• Optically isolated RS232 interface (19200 Bd, 8 data bits, no parity)
• BDM debug interface (non-optically isolated)
• 2.4 GHz RF interface through a 1320x-RFC RF daughter card (optional only)
• 2.4 GHz RF interface through a 1322x low power node daughter card
• Powered by 3.3 V SMPS open-frame module (3-rd party solution)
• All components (board, sensors, and SMPS) are built into a plastic box with a
transparent cover
• EMC proven design (EN61000-4-2, EN610004-4)
• Power meter demo mechanical dimension — 18 x 26 x 15 cm (w x l x h)
• Power meter demo weight — 1 kg approximately
1.2.2 Software features of the design
• Application C/ASM source code for CodeWarrior is available
• MQX based design for advanced markets
• Fast Fourier Transform (FFT) computing technique for precise reactive energy
measurement
• ZigBee SE2.0 stack implemented in 1322x low power node for connection to a
ZigBee® network
• FreeMASTER visualization script for calibration, watching, and so on.
• Serial bootloader for safe firmware upload through RS232, see application note
Developer's Serial Bootloader for M68HC08 and HCS08 MCUs (document
AN2295)
1.3 MCF51EM256 Microcontroller series
The MCF51EM256 is Freescale’s new smart-meter-on-a-chip 32-bit ColdFire® V1 core
microcontroller (MCU) with embedded LCD controller, 16-bit ADC, and metrologyspecific peripherals optimized for smart meter applications. The MCF51EM256 comes
with a full suite of hardware and software tools to make development quick and easy.
There is a block diagram of this MCU in Figure 1-1.
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MCF51EM256 Microcontroller series
The MCF51EM256 MCU provides the following main features:
• Operating at processor core speeds of up to 50.33 MHz (peripherals operate at half of
this speed) at 3.6 V to 2.5 V, and 20 MHz at 3.6 V to 1.8 V
• Up to 256 KB of flash memory
• Up to 16 KB of RAM
• Less than 1.3 µA of typical power consumption in battery mode, with the MCU
supply off
• Ultra-low power independent RTC with calendar features, separate time base, power
domain, and 32 bytes of RAM
• Integrated 16-bit SAR analog-to-digital converter
• Programmable Delay Block (PDB)
• Two analog comparators with selectable interrupt (PRACMP)
• LCD driver
• Three Serial Communications Interface modules (SCI)
• Three Serial Peripheral Interfaces (SPI)
• Inter-Integrated Circuit (IIC)
• Two 8-bit and one 16-bit Modulo Timers (MTIM)
• Two-channel Timer/PWM module (TPM)
• 80-pin LQFP or 100-pin LQFP package
• –40° C to +85° C operating temperature range
• RoHS compliant
Target applications of this MCU are:
• Smart metering
• Sensor collection
• Phase measurement units
• Industrial energy measurement
• 1-phase and 3-phase electricity meters
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Chapter 1 Introduction
Figure 1-1. MCF51EM256 block diagram
1.3.1 Peripheral application usage
The power meter concept benefits greatly from plenty of integrated internal peripherals in
the MCF51EM256 MCU.
The Analog to Digital Controller (ADC) features used in the application:
• Four channels are used, one is differential for CT current measurement, the second is
single-ended for voltage measurement. The remaining two channels are also singleended for shunt resistor current measurement (two gain stages)
• Linear successive approximation algorithm with a 16-bit resolution
• High-speed conversion (up to 128 samples per one period)
• 3.735 MHz module clock
• 16 hardware averaged samples to create a proper ADC result
The General Purpose Input Output (GPIO) features used in the application are:
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MCF51EM256 Microcontroller series
• Used for directly controlling some peripherals such as LEDs, open-collector, and so
on.
The Inter-Integrated Circuit (IIC) features used in the application:
• Primarily provides a method for internal communication between the meter (slave)
and the 1322x-LPN daughter card (master)—prepared for ZigBee communication
• Secondarily used for internal communication with the 3-axis digital accelerometer
MMA7660FC (optional only)—prepared for tamper detection
• Interrupt driven by byte-by-byte data transfer
• Communication up to 100 kbps with software selectable slave address
The Keyboard Interrupt (KBI) features used in the application:
• Used for reading the state of the buttons in interrupt mode
The Liquid Crystal Display (LCD) controller features used in the application:
• Up to 288 segments (4x40 is currently used)
• Used for data displaying
The 16-bit Modulo Timer (MTIM16) features used in the application:
• Free-running mode with interrupt is used
• Generates a precision time marks for zero-crossing
The PRACMP (Programmable Analog Comparator) features used in the application:
• Compares input voltage signal with a bias voltage (reference)
• Interrupt on rising edges is used
• Generates capture flags for zero-cross voltage signal detection. Due to this, a variable
time window for the PDB is generated
• Line frequency measurement
The Programmable Delay Block (PDB) features used in the application:
• Hardware triggering of the ADC channels
• Four individually controlled trigger conditions (one for each ADC channel)
depending on the phase shift of the sensors
The Real-Time Clock (RTC) features used in the application:
• Ultra-low power independent real time clock with calendar features (iRTC)
• Tamper detection and indicator
• Battery monitor output
The Serial Communication Interface (SCI1) features used in the application:
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Chapter 1 Introduction
• Provides communication interface with an external PC (for calibration, watching and
safe code uploading)
• Communication settings are—19200 Bd, 8 data bits, one stop bit, and no parity
The Serial Communication Interface (SCI2) features used in the application:
• Provides communication interface for the IEC1107 infrared communication port
(optional only)
The Serial Peripheral Interface (SPI) features used in the application:
• Provides internal communication interface for the1320x-RFC RF daughter card
(optional only)
The Voltage Reference (VREF) features used in the application:
• Provides a reference voltage for internal analog peripherals such as the ADC,
PRACMP
• Low-power buffer mode is used
1.4 1322x low power node (LPN)
The 1322x-LPN is one of the Freescale 1322x development kits designed for connecting
to a ZigBee network. The 1322x low power node is designed as a stand-alone
development board, including an MC1322x, two LEDs, two push buttons, a GPIO
connector, header pins, and a programming and debug port. Note that the ZigBee
capabilities of this board are only used in the MCF51EM256 metering concept – because
of this feature, the power meter can easily became part of the smart grid. The low power
node board is internally connected to an EM256 metering board via a IIC interface. Here
are the main features of the 1322x low power node board:
•
•
•
•
•
•
•
•
•
•
•
2.4 GHz wireless nodes compatible with the IEEE 802.15.4 standard
Based on the MC13224V Platform in a Package
Hardware acceleration for both the IEEE 802.15.4 MAC and AES security
Printed F antenna
Over-the-air data rate of 250 kbps
Typical range (outdoors, line of sight) is 300 meters
On-board expansion capabilities for external application-specific development
activities
Programmable flash
J-Tag port for reprogramming and in-circuit hardware debugging
Buttons and LEDs for demonstration and control
Connections for battery or external power supply
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1322x low power node (LPN)
The core of the 1322x low power node is the Freescale MC1322x 99-pin LGA Platformin-Package (PiP) solution that can be used for wireless applications ranging from simple
proprietary point-to-point connectivity to complete ZigBee mesh networking. The
MC1322x is designed to provide a highly integrated, total solution, with premier
processing capabilities, and very low power consumption. A full 32-bit ARM7TDMI-S
core operates up to 26 MHz. The RF radio interface provides for low cost and high
density as shown in Figure 1-2.
Figure 1-2. MC1322x RF interface
As described above, the 1322x low power node is used for connecting an EM256 power
meter to a ZigBee network. ZigBee, an IEEE® 802.15.4 standards-based solution, as
defined by ZigBee Alliance, was developed specifically to support sensing, monitoring
and control applications. The ZigBee solution offers significant benefits, such as low
power, robust communication and a self-healing mesh network. The ZigBee solution
frequencies are typically in the 868/915 MHz or 2.4 GHz spectrums.
The ZigBee data rate for technology solutions is 250 Kbps. ZigBee technology
theoretically supports up to 65,000 nodes. Common applications in sensing, monitoring
and control, which are best supported by a ZigBee technology solution include:
•
•
•
•
•
•
•
•
Personal and medical monitoring
Security, access control and safety monitoring
Process sensing and control
Heating, ventilation and air conditioning (HVAC) sensing and control
Home, building and industrial automation
Asset management, status, and tracking
Fitness monitoring
Energy management
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Chapter 1 Introduction
NOTE
For connection of the power meter to a ZigBee network via the
1322x-LPN daughter card, it is necessary to program the
1322x-LPN with the correct firmware. That description is out
of range of this design reference manual.
1.5 MMA7660FC 3-axis Xtrinsic accelerometer
The MMA7660FC is a digital output (IIC), low power, low profile capacitive micro
machined accelerometer featuring a low pass filter, compensation for 0 g offset and gain
errors and conversion to 6-bit digital values at a user configurable output data rate. The
device can be used for sensor data changes, product orientation, and gesture detection
through an interrupt pin (INT). The device is housed in an extremely small DFN package.
The EM256 metering concept is prepared for tamper detection – this means illegally
opening the cover of the power meter. However, the tamper function using a 3-axis IIC
accelerometer is only optional.
The MMA7660FC provides the main following features:
• Digital output IIC
• 3 mm x 3 mm x 0.9 mm DFN package
• Low power consumption—Off mode: 0.4 A, standby mode: 2 A, active mode:
47A at 1 ODR
• Configurable samples per second from 1 to 120 samples a second
• Low voltage operation:
• Digital voltage— 1.71 V – 3.6 V
• Analog voltage— 2.4 V – 3.6 V
•
•
•
•
•
•
•
Auto-wake and sleep feature for low power consumption
Tilt orientation detection for portrait and landscape capability
Gesture detection Including shake detection and tap detection
Robust design, high shocks survivability (10,000 g)
RoHS compliant
Environmentally preferred product
Low cost
Typical applications for this accelerometer are:
• Mobile phone/ PMP/PDA—Orientation detection, image stability, text scroll, motion
dialing, and tap to mute
• Laptop PC—Anti-theft
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MMA7660FC 3-axis Xtrinsic accelerometer
• Gaming—Motion detection, auto-wake and sleep for low power consumption
• Digital still camera—Image stability
There is a simplified accelerometer functional block diagram in Figure 1-3.
Figure 1-3. Simplified accelerometer functional block diagram
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Chapter 2
Basic Theory
2.1 Definition of terms
To understand the electricity metering theory, here are some definitions of basic terms.
2.1.1 Power
AC power flow has the three components — Real power (P) measured in watts (W),
apparent power (S) measured in volt-amperes (VA), and reactive power (Q) measured in
reactive volt-amperes (VAr).
Active power (P) also known as real power or working power is the power that actually
powers the equipment. As a rule, true power is a function of a circuit's dissipative
elements usually resistances (R).
Reactive power (Q) is a concept used by engineers to describe the loss of power in a
system arising from the production of electric and magnetic fields. Although reactive
loads such as inductors and capacitors dissipate no power, they drop voltage and draw
current that creates the impression that they actually do. This imaginary power or nonworking power is called reactive power (Q). If the load is purely inductive or capacitive,
then the voltage and current are 90 degrees out of phase (for a capacitor, current leads
voltage; for an inductor, current lags voltage) and there is no net power flow. This energy
flowing backwards and forwards is known as reactive power. Reactive power thus is
produced for system maintenance and not for end-use consumption. By convention, a
"lagging" or inductive load, such as a motor, will have positive reactive power. A
"leading", or capacitive load, has negative reactive power. Reactive power is a function
of a circuit's reactance (X).
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Definition of terms
Apparent power (S) is the vector summation of active and reactive power. It is the
product of a circuit's voltage and current, without reference to phase angle. Apparent
power is a function of a circuit's total impedance (Z).
These three types of power — true, reactive, and apparent relate to one another in a
trigonometric form. This is called a power triangle (see Figure 2-1). The opposite angle is
equal to the circuit's impedance (Z) phase angle. Apparent power is often computed from
this power triangle using the Pythagorean Theorem as:
Figure 2-1. Power triangle
A common utility system is often based on Total Apparent Power (Stot) measured also in
volt-amperes (VA). Total apparent power is a product of the RMS voltage and RMS
current, and is defined as:
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Chapter 2 Basic Theory
This a general proposition:
In a pure sinusoidal system with no higher harmonics, the apparent power (S) equals Stot.
If there are some higher harmonics in the mains, apparent power is not the same as total
apparent power, because the simple vector sum in apparent power computing loses
accuracy. Therefore, Stot is often used because it is more precise in these situations.
2.1.2 Energy
Energy is the accumulated power over a period of one hour.
Active energy means the electrical energy produced, flowing, or supplied by an electric
circuit during a time interval, being integral with respect to time of the instantaneous
active power and measured in units of watt-hours (Wh). For practical use in power
meters, a higher unit called a kilowatt-hour (kWh) is used, which is 1000 watt-hours
(Wh).
Apparent energy means the integral with respect to time of the apparent power. Kilovoltampere-hour (kVAh) is the unit for total (apparent) energy.
Reactive energy means the integral with respect to time of the reactive power. Kilovoltampere-reactive-hour (kVArh) is the unit for reactive (non-working) energy.
2.1.3 Power factor
The power factor of an AC electric power system is defined as the ratio of real power
flowing to the load to the apparent power in the circuit, and is a dimensionless number
between 0 and 1 (frequently expressed as a percentage, that is 0.5 pf = 50% pf). Real
power is the capacity of the circuit for performing work in a particular time. Apparent
power is the product of the current and voltage of the circuit. Due to energy stored in the
load and returned to the source, or due to a non-linear load that distorts the wave shape of
the current drawn from the source, the apparent power will be greater than the real power.
In an electric power system, a load with a low power factor draws more current than a
load with a high power factor for the same amount of useful power transferred. The
higher currents increase the energy lost in the distribution system and require larger wires
and other equipment. Because of the costs of larger equipment and wasted energy,
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Electricity distribution
electrical utilities usually charge a higher cost to industrial or commercial customers
where there is a low power factor. Therefore, a modern electronic smart power meter
must also measure the power factor.
Power factor is defined as:
is the phase angle between voltage and current.
When power factor is equal to 0, the energy flow is entirely reactive. Stored energy in the
load returns to the source on each cycle. When the power factor is 1, all the energy
supplied by the source is consumed by the load. Power factors are usually stated as
leading or lagging to show the sign of the phase angle. It is often desirable to adjust the
power factor of a system to near 1.0.
2.2 Electricity distribution
Electricity distribution is the final stage in the delivery of electricity to end users. A
distribution system's network carries electricity from the transmission system and
delivers it to consumers. Part of what determines the design of the electricity meter is the
transmission supply design, the most common residential arrangements being:
• 1-phase, 2 wire (1P2W) — Europe and Asia 220 V-240 V, US 2-wire 110 V
• 1-phase, 3 wire (1P3W) — US 3-wire, sometimes called 2-phase
• 3-phase, 4 wire (3P4W)
The 1-phase 2-wire installation is the most common form of electricity distribution in the
world. Finally, more than 80% of the population in the world uses a 1-phase 2-wire
installation of 230 V/50 Hz (see at Figure 2-2). Much of the US installation is 110 V/60
Hz 1-phase 2-wire. The electricity meter described in this design reference manual is
designed for use in 1P2W installations.
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Chapter 2 Basic Theory
Figure 2-2. Residential voltage and frequency worldwide
2.3 Electricity meters
An electric meter or energy meter is a device that measures the amount of electrical
energy consumed by a residence, business, or an electrically powered device. Electric
meters are typically calibrated in billing units, the most common is the kilowatt hour.
Periodic readings of electric meters establish billing cycles and energy used during a
cycle.
The most common unit of measurement on the electricity meter is the kilowatt hour
(kWh), which is equal to the amount of active energy used by a load of one kilowatt over
a period of one hour, or 3,600,000 joules. Some electricity companies use the SI
megajoule instead. Similarly to active energy in kWh, there is also defined a reactive
energy (kVArh) and apparent energy (kVAh), see Section 2.1.2 Energy .
Electricity meters operate by continuously measuring the instantaneous voltage (volts)
and current (amperes) and finding the product of these to give instantaneous electrical
power (watts) which is then integrated against time to give energy used (joules, kilowatthours and so on.). Meters for smaller services (such as small residential customers) can
be connected directly in-line between source and customer. For larger loads, more than
about 200 amps of load, current transformers are used, so that the meter can be located
other than in line with the service conductors.
The standard electricity meters fall into two basic categories, electromechanical and
electronic.
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Electricity meters
2.3.1 Electromechanical meters
The most common type of electricity meter is still the electromechanical induction watthour meter. These meters will be progressively substituted by fully electronic meters
because of many additional advantages of these meters (see Section 2.3.2 Electronic
meters).
The electromechanical induction meter operates by counting the revolutions of an
aluminium disc that is made to rotate at a speed proportional to the power. The number of
revolutions is proportional to the energy usage. It consumes a small amount of power,
typically around 2 watts.
The metallic disc is acted upon by two coils. One coil is connected in such a way that it
produces a magnetic flux in proportion to the voltage, and the other produces a magnetic
flux in proportion to the current. The field of the voltage coil is delayed by 90 degrees
using a lag coil. This produces eddy currents in the disc and the effect is such that a force
is exerted on the disc in proportion to the product of the instantaneous current and
voltage. A permanent magnet exerts an opposing force proportional to the speed of
rotation of the disc. The equilibrium between these two opposing forces results in the disc
rotating at a speed proportional to the power being used. The disc drives a register
mechanism that integrates the speed of the disc over time by counting revolutions, much
like the odometer in a car to render a measurement of the total energy used over a period
of time.
2.3.2 Electronic meters
Electronic meters display the energy used on an LCD or LED display, and can also
transmit readings to remote places. In addition to measuring energy used, electronic
meters can also record other parameters of the load and supply such as maximum
demand, power factor, reactive power used, and so on. They can also support time-of-day
billing, for example, recording the amount of energy used during on-peak and off-peak
hours.
A typical electronic power meter has a power supply block, a signal conditioning circuit,
a metering engine (AFE), a processing and communication engine (that is, a
microcontroller), and other add-on modules such as RTC, LCD, communication ports and
modules, and so on. A basic block outline of the electronic power meter, see Figure 2-3.
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Chapter 2 Basic Theory
User
Selection
voltage
current
analog
Signal
Conditioning
AFE
digital
MCU
ADC
LCD
AMR
Communications
Figure 2-3. Basic outline of the electronic power meter
The signal conditioning circuitry is used for adapting a high-amplitude signal from the
mains to a lower one, accepted by the AFE (ADC).
The metering engine is given the voltage and current inputs, has a voltage reference,
samplers. and quantisers followed by an ADC section to yield the digitised equivalents of
all the inputs. All of this is sometimes called the Analog Front-End (AFE). These inputs
are then processed using a DSP or MCU to calculate the various metering parameters
such as powers, energies, and so on.
The processing and communication section has the responsibility of calculating the
various derived quantities from the digital values generated by the metering engine. This
also has the responsibility of communication using various protocols and interfaces with
other add-on modules connected as slaves.
RTC and other add-on modules are attached as slaves to the processing and
communication section for various input and output functions. On a modern meter, most
if not all of this is implemented inside the microprocessor, such as the Real Time Clock
(RTC), LCD controller, temperature sensor, memory, and analog to digital converters.
One of the important features of the modern electronic power meter is AMR technology.
The AMR is the technology of automatically collecting consumption, diagnostic, and
status data from energy metering devices and transferring that data to a central database
for billing, troubleshooting, and analyzing. This advance mainly saves utility providers
the expense of periodic trips to each physical location to read a meter. Another
advantage, is that billing can be based on near real time consumption rather than on
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Voltage and current measurement
estimates based on previous or predicted consumption. This timely information coupled
with analysis, can help both utility providers and customers to better control the use and
production of electric energy. Electronic meters with AMR technology can read and
communicate through several mechanisms such as:
•
•
•
•
•
•
Infrared
Radio frequency
Data modem (via a telephone line)
Power line carrier
Serial port (RS-485)
Broadband
AMR meters often have sensors that can report the meter cover opening, magnetic
anomalies, extra clock setting, stuck buttons, inverted installation, reversed or switched
phases, and so on. These events may be immediately sent to the utility company thanks to
AMR technology.
Smart meters go a step further than simple AMR. They offer an additional function,
including a real-time or near real-time reading, power outage notification, and power
quality monitoring. They allow price setting agencies to introduce different prices for
consumption based on the time of day and the season. The feedback they provide to
consumers has also been shown to cut overall energy consumption.
In comparison to traditional mechanical or electromechanical power meter solution, the
electronic meters offer the utility market several additional advantages including:
•
•
•
•
•
•
•
•
Improved immunity and reliability
Higher accuracy
Higher security
Support of a wide range of power factor loads
Calibration is easier
Anti-tampering protection including traditional or modern solutions
Automated meter reading (AMR)
Advanced billing methods (prepay, time-of-use, an so on.)
2.4 Voltage and current measurement
In electricity meters the energy is calculated from two measured signals, voltage and
current. For line voltage and line current measurement, systems that are generally called
sensors are used. Whichever sensor is used for voltage and current measurement results
in an AC voltage with a magnitude proportional to the signal being measured.
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Chapter 2 Basic Theory
The voltage sensor results in a sine wave with a fundamental frequency typically either
50 Hz or 60 Hz depending upon the power distribution used, see Section 2.2 Electricity
distribution.
For current measurement, the sensor provides a fundamentally sinusoidal signal (possibly
with harmonics) which may lag or lead the voltage signal depending upon the load.
A typical simplified configuration for metering voltage and current in a 1-phase 2-wire
installation is shown in Figure 2-4. There are three typical sensors used for sensing
current and voltage in power meters. All of these sensors are also used in the electronic
power meter described in this manual.
Figure 2-4. Typical measurement circuit in 1P2W installation
The following sections describe the most used methods for sensing voltage and current
used in the electronic power meters.
2.4.1 Voltage divider
A voltage divider is used for voltage measurement. In a practical implementation,
multiple series resistors are used instead of R1to limit the power dissipation and reducing
heat generated thus improving accuracy, see Figure 2-4.
The equation for computing output voltage of the voltage divider is defined as:
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Voltage and current measurement
Where Vin is the phase voltage and Vout is the voltage measured by the ADC (voltage
drop at R2).
The voltage divider can be selected to more closely meet the specification of the ADC.
2.4.2 Shunt resistor
A shunt resistor is used to sense the current primarily due to the fact it does not distort the
signal and is extremely low cost in comparison to other current measurement methods.
The downside of using a shunt resistor is primarily the power dissipation that can create
inaccuracies in the measurement due to resistive changes and due to temperature and
waste of power. To limit the self heating effect of the shunt, the resistor is made using a
metal with suitable properties. The resistance of the shunt is kept very low to reduce the
power dissipation.
Typically, shunt resistors are in the range of 100 μΩ to 300 μΩ and as such the voltage
developed across them is very small. For example, 100 A drawn through a 200 μΩ shunt
develops only 20 mV (Voltage = current * resistance) through a 300 μΩ shunt this would
be 30 mV, which develops 2 W power loss and 3 W respectively.
The problem of this approach is the very small voltages derived from the shunt resistor
and the even smaller resolution of valid measurements. Therefore, a signal derived from
the shunt resistor must be amplified to keep the correct measurement precision. An
Operational Amplifiers are frequently used for this purpose (see Figure 2-4).
There are several rules for a right selection of a shunt resistor in the application:
• A shunt resistor must have good thermal properties (that is Manganin-Alloy with a
low temperature coefficient of resistance)
• Select the shunt size to maximize the dynamic range of the ADC input
• Minimize the power dissipation in the shunt resistor
NOTE
Power dissipated by the shunt resistor plus the power supply
used by the meter, must be below the specification for the meter
(IEC1036 specifies a 2 W total power loss).
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Chapter 2 Basic Theory
2.4.3 Current transformer
Current Transformers (CT) are used extensively for measuring current and monitoring of
the power grid. Like any other transformer, a current transformer has a primary winding,
a magnetic core, and a secondary winding. The alternating current flowing in the primary
produces a magnetic field in the core, which then induces a current in the secondary
winding circuit, see Figure 2-5. The CT is typically described by its current ratio (N)
from primary to secondary. Relative to current output of the CT, it is necessary to use an
external current to a voltage converter, such as a burden resistor Rb (see Figure 2-4), in
systems where the voltage input of the ADC is used in the majority of applications. The
primary objective of the current transformer design is to ensure that the primary and
secondary circuits are efficiently coupled, so that the secondary current bears an accurate
relationship to the primary current.
Benefits of using a CT are that the output voltage can easily be matched to the capability
of the ADC input by selecting appropriate winding or appropriate burden resistor (Rb),
because of this, an OpAmp pictured at Figure 2-4 is not necessary. The next important
benefit of using a CT is that this sensor isolates the measuring engine from the mains,
therefore the CTs may be easily used in polyphase meters.
A typical feature of a CT is the time shift (delay) between the primary and secondary
currents in the windings. For using this in the power meters, it is good to know that the
power meters must wait a specific time after the voltage measurement before reading the
current from the CT. The delay required is specific to each CT and is established during
calibration of the meter and programmed into the meter; as a part of calibration constants.
CT coils have the negative effect of distorting the current measurement. Considering the
magnetic core of the CT, it is necessary to respect a maximum recommended current in
the primary winding (rating factor) because of saturation of its core. A good accuracy in
the case of CT current measurement is directly related to other factors, including external
electromagnetic fields and a change of temperature.
Figure 2-5. Current transformer principle
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Voltage and current measurement
2.4.4 Rogowski coil
A Rogowski coil is an electrical device for measuring alternating current (AC) or high
speed current pulses. It consists of a helical coil of wire with the lead from one end
returning through the centre of the coil to the other end, so that both terminals are at the
same end of the coil, see Figure 2-6. The whole assembly is then wrapped around the
straight conductor whose current is to be measured. Because the voltage that is induced in
the coil is proportional to the rate of change (derivative) of current in the straight
conductor, the output of the Rogowski coil is usually connected to an electrical, or
electronic integrator circuit to provide an output signal that is proportional to the current.
One advantage of a Rogowski coil over other types of current transformers is that it can
be made open-ended and flexible, allowing it to be wrapped around a live conductor
without disturbing it. Because a Rogowski coil has an air core rather than an iron core, it
has a low inductance and can respond to fast-changing currents. Also, because it has no
iron core to saturate, it is highly linear even when subjected to large currents, such as
those used in electric power transmission, welding, or pulsed power applications. A
correctly formed Rogowski coil with equally spaced windings is largely immune to
electromagnetic interference.
Benefits of using a Rogowski coil are similar to using a CT, namely that the output
voltage can more easily be matched to the capability of the ADC input by selecting an
appropriate winding, load resistor and filter. Another advantage of a Rogowski coil, is the
lower cost than a traditional CT, although it requires an integrator and additional phase
compensation.
Figure 2-6. A Rogowski Coil Principle
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Chapter 3
System Concept
3.1 Application description
A standard system block diagram of the MCF51EM256 power meter concept is described
in Figure 3-1. The full-metering system solution, that is all the components inside of the
green-dashed rectangle, incorporate these parts:
• Metering board, inside the grey-dashed rectangle — The main metering engine, here
is the concentrated majority of metering components
• Switch Mode Power Supply board — SMPS, this board is used for supplying the
metering engine and the 1322x-LPN daughter card
• External current sensors (CT, shunt resistor) — Located directly to the mains power
connector inside the metering case
• 1322x-LPN — Daughter card for ZigBee communication
• Power Meter case with an integrated mains power connector and RS232
communication connector
Some common parts of the power meter in the block diagram have the same color for
better function identification, mainly the voltage and current sensors (red color), see
Figure 3-1. There are two current sensors in the power meter; shunt resistor and current
transformer, both are located near the mains power connector inside the power meter
case, outside the metering board. There is voltage measurement sensor (voltage divider)
which is located directly on the metering board.
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Application description
Figure 3-1. MCF51EM256 power meter block diagram
3.1.1 Metering board
The metering engine (board) is the main part of the power meter. Here are concentrated
components such as: the MCU with AFE, signal conditioning part, LCD, buttons, LEDs,
optical interface for the IEC1107 and RS232, voltage sensor, tamper button, 3 V battery,
accelerometer, and connector for the 1320x-RFC daughter card. The metering board is
designed on a two-sided printed circuit board. Most of the components are soldered on its
top side (see Figure 3-2), with only some connectors soldered on the bottom side of this
PCB, (see Figure 3-3).
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Chapter 3 System Concept
Battery
BDM
Interface
Display
Infrared
Interface
User LED
OC
Interface
Bias
Voltage
for OpAmps
RS232
Interface
EOC
Interface
CT Signal
Conditioning
Part
(full configuration)
CT Signal
Conditioning Part
(low-cost configuration)
LED
Interface
Shunt Resistor
Signal
Conditioning Part
Tamper
Button
Voltage Divider Reset
Signal
Button
Conditioning Part
LED Kvarh
LED KWh
MCU
XTAL
Power-on
LED
User Buttons
MRAM
Accelerometer
Interface
Figure 3-2. Top side metering board view
Open-collector
interface
RS232
interface
EOC
interface
1322x-LPN or
accelerometer
interface
1320x-RFC
interface
Power
supply
Voltage
interface
Shunt
interface
CT
interface
Figure 3-3. Bottom side metering board view
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Application description
The core of the metering engine placed on the top side of the PCB is the 32-bit Coldfire
V1 microcontroller, called the MCF51EM256 (for a description see Section 1.3
MCF51EM256 Microcontroller series). All of the MCU peripherals except for the BDM
interface, which are currently used in the application are pictured in the block diagram in
Figure 3-1.
A simplified function of the MCU in the application is as follows:
The ADC primarily reads data from voltage and currents sensors. The MCU computes
other values like powers, energies, power factor, and line frequency consecutively. The
MCU communicates with the user via the built-in HMI (LCD+buttons) or via several
communication interfaces (RS232, ZigBee, IEC1107, LEDs, OC). A description of the
metering algorithm is the content of this design reference manual, but it is described in
application note titled FFT-based Algorithm for Metering Application (document
AN4255).
The HMI of this power meter is comprised of these parts: LCD, two user push-buttons,
and one user (yellow) LED. On the LCD, the user can see plenty of computed values,
such as the RMS value of line voltage and current, powers, energies, power factor, line
frequency, and also actual time and date. By using the two push-buttons, the user can
select one of these values to be shown on the LCD.
NOTE
There is only one value shown on the LCD at one time. The
user yellow LED is part of the open-collector (OC) interface.
The next important part of the metering engine board is the signal conditioning part. This
part is used for adapting the signal level from sensors to the AFE (part of the MCU
included ADC, VREF, and so on). There are several different types of signal conditioning
parts with regards to sensors used: the part for voltage measurement is made of a simple
voltage divider, which is also described as the voltage sensor in this Design Reference
Manual. The part for current measurement via a shunt resistor is made from two
operational amplifiers (only one is pictured in the simplified block diagram in Figure 2-4)
with a resistive feedback network which produce two voltage signals with different gains
(26x and 520x approximately). The current measurement via the current transformer (CT)
is made in the first level by a burden resistor which works as a simple current to voltage
converter. This connection produces only one-gained voltage measurement. The second
level of signal conditioning for the current measurement via the CT is optional (dotted
symbol for the OpAmp in the block diagram). This is done by several operational
amplifiers, also with a resistive feedback network that produces two voltage level signals
with different gains; because of this, a two-gained voltage measurement is executed
(similar to the current measurement via a shunt resistor).
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Chapter 3 System Concept
There are several communication interfaces on the metering board. The interface for
RS232 is optically isolated via optocouplers and the interface for the IEC1107 is optically
isolated via infrared components. The open-collector is a non-optically isolated output of
the power meter – this may be used for switching some small loads (up to 1.6 W). One of
the most interesting types of communication in this power meter is RF or ZigBee.
Communication via RF/ZigBee is done primarily by the external 1322x-LPN daughter
Card (outside the metering engine) which communicates with the metering board through
the IIC interface. Secondarily, the RF communication may be done via the 1320x-RFC
daughter card which communicates with the metering board through the SPI interface.
But the preferential type of RF communication in this Power Meter is through external
1322x-LPN board (the IIC interface between the boards). Finally, two red LEDs are used
for optical communication with utility service provider – this is energy output interface,
the first LED is here for active energy counting and the second LED is for reactive
energy counting.
The essential parts of the metering board are components for proper function of the RTC
part of the MCU, including the 3 V battery (for saving date and time), crystal and
external tamper push-button. The tamper push-button is used only for simulation
purposes in this power meter, because it needs user interaction. But in true power meters
this button is hidden inside of the power meter and waits for the cover opening by the
user – in this case, the illegal interference to the metering engine is detected.
The other way of tamper detection in this power meter may be by using a 3-axis IIC
accelerometer—the MMA7660FC silicon may be used for that. The MCF51EM256
power meter currently does not use this type of tamper detection, however the interface
for it is now prepared. An illegal cover opening can cause a 3-axis motion that which can
be detected by this accelerometer. Then some kind of sophisticated algorithm must be
used consecutively, because this event must be filtered from ordinary motions of the
power meter and interpreted as an illegal cover opening. But this type of tamper detection
is only optional, primarily the tamper push-button is used for that.
3.1.2 Switch mode power supply board connection
The SMPS board is used for supplying the metering board engine. The SMPS used in this
application is a 3-rd party open-frame solution for the power supply that produces one
galvanic-isolated level of output voltage. This open-frame SMPS module has a wide
range of input AC voltages beginning at 85 V RMS up to 264 V RMS with a wide range
of mains frequency (47 Hz to 63 Hz) too. Thanks to input parameters of this SMPS, the
whole power meter can work with mains of these voltage and frequency ranges. The
output voltage is fixed to a 3.3 V DC level with 1.3 A nominal output current, and the
power rating is then 4.3 W. The board overview is in Figure 3-4. There are two power
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Application description
connectors on this board—on the left side there is an input socket for connection to the
mains (L_inp, N_inp), and on the right side there is an output socket for supplying the
board. The SMPS is screwed onto the bottom part of the power meter case and connected
to the mains and metering board via two thin cables.
+3.3V
N_inp
L_inp
GND
Figure 3-4. SMPS board view
3.1.3 External current sensors connection
There are two types of external current sensors as was described above: shunt resistor and
current transformer. For the correct mains current measurement in the basic power meter
configuration, only one of these sensors is required. In the full metering configuration,
two sensors are used. In this configuration, the shunt resistor is used for phase current
measurement, the CT is used for neutral current measurement.
LINE_IN LINE_OUT
GND
L_inp
L_out
Figure 3-5. Shunt resistor description
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Chapter 3 System Concept
The shunt resistor is mainly a MANGANIN® resistor of an accurately known resistance,
in this case 150 μΩ . This shunt resistor is intended for current measurement of up to 100
A RMS. The voltage drop across the shunt resistor is proportional to the phase current
flowing through it, because its resistance is known, a small voltage drop is amplified by
operational amplifiers, and then measured by the internal ADC of the MCU. For a photo
of this shunt resistor see Figure 3-5.The terminal connection of this shunt resistor is
divided into two parts—power connection and sense connection, because of this, a 4-wire
current measurement may be done. The power connection is intended for a connection
between the phase input (L_inp) and phase output (L_out) connectors. The sense
connection of this shunt resistor is intended only for measuring its voltage drop.
NOTE
There is also a separated ground terminal in the sense
connection area for the metering board ground connection. This
ground terminal is located on the same side as the power phase
input (L_inp).
The CT is also used for current measurement. In the basic configuration (low-cost), it is
intended for phase current measurement equally to the shunt resistor, but in a full-system
configuration (where a shunt resistor is used) the CT is used for neutral current
measurement. The primary winding of this CT is created from a one-coil hard wire,
connected between the phase input and phase output terminals (basic configuration), or
between the neutral input and neutral output terminals (full-system configuration). In
fact, this hard wire connection is executed by several (two) wires connected in parallel.
For a maximum flowing current of 100 A RMS, a minimum of 16 mm2 of conductor
cross-section is required. There is a CT description in Figure 3-6.
Gap for
primary winding
Secondary winding
termination
Figure 3-6. Current transformer description
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Application description
3.1.4 1322x-LPN connection
The 1322x-LPN is intended for use of a ZigBee node for the power meter. It works as an
inter-mediator between the power meter and a ZigBee coordinator which is based at the
utility provider area for example. The ZigBee coordinator scans data from numerous
equipment (power meter, home thermostat, sensor, dimmer switch, and so on.) in the
ZigBee network and sends it to the central (PC) station. The 1322x Low Power Node is
screwed on the bottom part of the power meter case, similar to where the SMPS is, and
connected as a daughter card to the metering engine through a thin flat cable. The board
overview is in Figure 3-7. There are two (optionally three) pairs of wires for its
connection to the metering board: the first pair is for supplying the node (3.3 V, GND),
the second pair is for the IIC communication lines (SCL,SDA), and the last optional pair
is for resetting the node by the external RESET push-button which is placed on the
metering board.
NOTE
The RESET push-button is used primarily for supplementary
resetting the metering board, but for resetting the 1322x-LPN
there are unused pins for doing this.
IIC connections
Power
connection
arrea
+
Reset pin
Figure 3-7. 1322x-LPN Board View
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Chapter 3 System Concept
3.1.5 Power meter case
Placed in a power meter case are all the components mentioned (boards, sensors, and so
on). It is made as a base with the terminal compartment cover, an EPDM gasket, and a
smoked transparent cover with a PUR gasket. It is intended primarily for DIN-rail
mounting in a vertical position (for example, on the wall ). Ingress protection of this case
is IP65, but due to apertures for push-buttons, it is downgraded to IP42. Because of the
transparent cover, the metering board with all its components, including the LCD
primarily are easily visible.
Spacer
RS232 flat cable & connector
Spacer
SMPS
CT
Primary winding for CT
N_out
N_inp
L_out
L_inp
Metering Board
Spacer
1322x-LPN
Shunt Resistor
Spacer
Figure 3-8. Power meter case — inside view
Figure 3-8 shows a photo of the metering case. You can see the boards and the current
sensor placements. There are also three or four power terminals in the terminal
compartment section. The number of terminals (3 or 4) depend on the system
configuration—basic with one current sensor (three terminals), or full-system with two
current sensors (four terminals). The main metering board is screwed onto four spacers
on the front side of the power meter case. On the bottom inside of the case there are the
SMPS and 1322x-LPN daughter card. The shunt sensor is soldered directly between the
two left power terminals (L_inp,L_out), and the CT sensor with its hard-wires, is
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Application usage
connected between the two right power terminals (N_inp,N_out). On the right side of this
case, there is an RS232 connector, which is connected to the main board via a thin 9-pin
flat cable.
3.2 Application usage
3.2.1 Power meter hardware configuration
This power meter is primarily used for demonstration purposes of the MCU used in a
single-phase two wire installation. For a better practical demonstration of the power
meter, the metering case is placed on a perspex base where an outlet is also placed (for
load connection) and a cable with a plug (for connection to the power mains). The whole
configuration is also called the power meter demo, see Figure 3-9.
SW2
Tamper SW1
Reset
Transparent
cover
Metering
engine
Case
Terminal
compartment
Plug
Pedestal
Outlet
Figure 3-9. The power meter demo view
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Chapter 3 System Concept
Although the current range of this power meter is internally set for a current measuring of
up to 100 A, for practical use this range is decreased to approximately 16 A, adequate for
demonstration purposes. This is caused by a maximum current rating of the outlet and
plug used. For customers who want to use the whole metering range up to 100 A, both
the plug and outlet must be replaced by more powerful ones.
For remote data communication the RS232 port may be used or the in-built ZigBee node.
Some communication interfaces, like an open-collector and so on are not directly
accessible.You must first open the cover of the case to access their connections.
3.2.2 Application example
The power meter demo can work in several hardware configurations, depending on the
current sensors used. In the basic or low-cost configuration it works only with one current
sensor, the shunt resistor or CT described in Section 3.1.3 External current sensors
connection. One of these sensors can measure line current only. The full metering
configuration allows measuring of not only the line current, but also the neutral current.
Because of this, several tampering techniques may be used for protecting against hacking
in the energy systems. For example, against a partial earth fault condition. An earth fault
means some of the load is connected to another ground potential and not the neutral wire.
Figure 3-10 shows a normal connection in a full-metering configuration and how the
phase and neutral wires are connected to the single-phase power meter.
NOTE
The current going through the phase wire is the same as that
coming out of the neutral wire (IP=IN).
Figure 3-11 shows a partial earth condition where one of the loads is connected to the
ground and thus part of the return current I2 does not go through the meter. Thus the
current in the neutral wire IN is less than that in the phase or live wire (IP). To detect this
condition, the power meter firmware monitors the current on both energy wires, phase
and neutral, and compares them. If they differ significantly, the firmware uses the larger
of the two currents to bill the energy and signals a fault condition. This is one of the
tampering events in the power meter.
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Application usage
phase neutral
Single Phase Energy Meter
IP
L_inp
Fault
shunt
L_out
N_inp
IN
metering
engine
CT
N_out
I1
I2
Figure 3-10. Normal phase neutral connection for 1-ph power meter
phase neutral
Single Phase Energy Meter
IP
L_inp
Fault
shunt
L_out
N_inp
IN
metering
engine
CT
N_out
I1
I2
Figure 3-11. Partial earth fault condition
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Chapter 4
Hardware Design of the Metering Board
4.1 Introduction to hardware implementation
This chapter describes the design of the application hardware, that is the design of the
metering board (engine). The main hardware is divided into two main parts, digital
hardware (HW) and analog hardware. Analog HW is also called signal conditioning in
this manual. Both of these parts are configurable depending on the customer request,
from a low-cost up to a high performance configuration. The stand-alone section of the
metering board is the power supply section, this is a mandatory part of each configuration
of the power meter. There are also plenty of test points in some important parts of the
metering board for primarily metering and testing purposes.
4.2 Power supply
The power supply section is used only for adapting the voltage level from the external
SMPS to the internal board, including also the overvoltage protection and signalize
function (LED) - see Figure 4-1. Connector J1 placed on the bottom side of the PCB is
the input power supply connector of the board. This connector must be joined to the
external SMPS, therefore, pin 1 of connector J1 to 3.3 V on the SMPS and pin 2 of the
connector J1 to the GND of the SMPS.
As you can see, there is a simple overvoltage protection including the Zener diode D1
and D3. These diodes protect against a reversing of polarity.
Some circuits of the whole design require two separate power supply levels, a digital and
analog power supply. The analog power supply level is separated from the digital part of
the power supply by the chip inductors L1 and L2 with filters (C5―C7) co-operation. The
analog power supply level is consequently marked +3.3 VA in the schematic, analog
ground is then marked GNDA.
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Digital hardware
For presence of an external power supply level (from the SMPS) there is a green LED D2
in the power supply section.
+3.3V
B
CON_2_TB
1
+3.3VA
1
2
D1
GND
1
A
MMSZ5231BT1G
J1
D2
WP7104LGD
+
C3
47UF
C1
0.1UF
GND
2
5.1V
R2
330
GND
GND
GND
L1
C4
100PF L2
1
1uH
1uH
2
2
C5
C6
0.1UF
100PF
+ C7
47UF
D3
MMSZ5231BT1G
5.1V
GNDA
GND
Figure 4-1. Power supply part of the metering board
4.3 Digital hardware
4.3.1 MCU core
The MCU is the core of the metering board. It is marked U1 in the schematics. The MCU
core with all key components are diplayed in the digital section of the schematic in
Figure A-1 or Figure A-3. For the MCU to function correctly, several components are
necessary:
•
•
•
•
Filters C8–C12, C48
Crystal Y1
Battery BT1 (for RTC only)
Tamper push-button TAMPER1 for simulation only (for RTC only)
Analog circuits (ADC, PRACMP) are also present in the MCU, therefore analog power
supply is necessary for supplying it.
Another part of the the MCU core, which we may simply assign to it, is the HMI. These
components include the display LCD1 and the two user push-buttons SW1 and SW2 with
simple filters C13, C17. Pull-up resistors for the buttons are software selectable by the
MCU. The charge pump for the LCD is the part of the MCU. Therefore, only minimum
external components regarding the LCD are required, in fact, only capacitors C14, C15,
C16, and C18.
Connector J3 is the BDM interface for MCU programming. Be careful about
programming the MCU through this interface in the configuration where the power meter
demo is fed from the mains. This interface is not isolated from the mains, therefore an
electric shock can arise. To prevent this, use an external optically isolated BDM interface.
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However, the best solution for MCU re-programming is using the bootloader in cooperation with the optically isolated RS232 data line (see at Section 5.2.3 Code
reprogramming via serial bootloader).
There is a RESET1 push-button that can reset not only the MCU, but also the external
1322x-LPN daughter card, this is because of the unused pins 4 and 5 of this button. Here,
this button is only for evaluation purposes in real power meters there is no room nor
reason for it.
The auxiliary part of the MCU core is an external universal SPI MRAM, whose density is
1 Mb.
4.3.2 RS232 interface
This interface is primarily used for a basic set-up of software for the meter, this includes
calibration and checking sensor outputs. The second function of this interface is
programming the power meter from a PC by a bootloader (see Section 5.2.3 Code
reprogramming via serial bootloader). Communication is optically isolated through
optocouplers ISO1 and ISO2. Because of using two additional signals on the serial data
line, RTS and DTR, the secondary side of ISO1 and the primary side of ISO2 are
powered from the RS232 data line (from the PC side). These signals are normally used
for transmission control, but this function is not used in the application, it is because of
the fixed voltage level on these control lines used for supplying these optocouplers, in cooperation with others components. These components include, D6–D8, C19, R7, and
R13. The part of the schematic including the RS232 communication interface can be seen
in Figure 4-2.
TP5
ISO1
R7
4.7K
SFH6106-4
R9
1.0K
C19
ISO2
2.2UF
1
+
3
D7
2
R13
470
TP6
4
1 1
SFH6106-4
D8
MMSD4148T1G
4
+3.3V
2
RS232_TXD
RS232_RXD
RTS
2
1
(+12V)
1
3
R6
330
MMSD4148T1G
2
D6
J5
RXD
TXD
DTR
GND
1
3
5
7
9
2
4
6
8
10
CON_2X5
2
MMSD4148T1G
GND
Figure 4-2. RS232 communication interface of the metering board
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Digital hardware
4.3.3 Infrared interface (IEC1107)
This interface uses infrared components, the high efficiency IR emitting diode D9, and
the NPN phototransistor Q3. Both of these are through-hole assembled. Other than these,
some necessary passive components are used such as R8, R10, R12 and C21. The part of
the schematic including the IEC1107 communication interface can be seen in Figure 4-3.
TP7
+3.3V
C21
Q3
OP506B
2
0.1UF
2
IR_RX
TP8
R8
680.0
R10
22K
R12
1.0K
1
IR_TX
IR_RX
TSAL4400
GND
1
GND
D9
GND
Figure 4-3. IEC1107 part of the metering board
4.3.4 User interfaces
The part of the schematic including both user interface parts can be seen in Figure 4-4.
One of these interfaces is also called the open-collector interface (OC). It has two
functions, primarily, it is used for switching some small loads up to 1.6 W, by using the
NPN transistor, Q1. It switches the voltage level 3.3 V through an external load to GND.
The second function of the user interface optically signalizes some program states via a
yellow LED D4 that may be used for debugging purposes.
NOTE
The user interface uses the same control signal from the MCU
for OC interface and for LED controlling.
2
+3.3V
LED_USR
R3 1
220
EOC_PULSE
R14
330
2
3
EOC_OC 2
EOC_OE 1
TP9
GND
1
ISO3
A
Q1 J2
MMBTA42
2
220
R4
3
1
CON_2_TB
B
D4
+3.3V
1
CON_2_TB
B
A
J7
4
SFH6106-4
2
WP7104LYD
GND
Figure 4-4. Two user interface parts of the metering board
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Chapter 4 Hardware Design of the Metering Board
There is also one general purpose user interface, called the EOC interface. This interface
is optically isolated through optocoupler ISO3. Output from this interface is accessible on
the connector J7.
4.3.5 LED interface
The LED interface is used for energy counting. There are two separate high-efficiency
red LEDs for doing this, D5 for active energy counting and D15 for reactive energy
counting. Both of these LEDs are through-hole assembled for a better placement near the
cover. The part of the schematic including the LED interface can be seen in Figure 4-5.
LED_kVarh
R59
330
LED_kWh
R5
330
2
D15
1
WP7104LSRD
D5
2
1
+3.3V
WP7104LSRD
Figure 4-5. LED part of the metering board
4.3.6 SPI interface
This interface is used exclusively for joining the 1320x-RFC daughter card to the
metering board through the 40-pin header J8. Communication between the boards uses
SPI data lines. The part of the schematic including the SPI communication interface can
be seen in Figure 4-6.
J8
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
RF_RESET
RF_ATTN
SPI1_SCK
SPI1_MISO
GND
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
IRQ
RF_RTXEN
SPI1_MOSI
RF_CE
+3.3V
CON_2X20
Figure 4-6. SPI Interface Part of the Metering Board
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Digital hardware
4.3.7 Accelerometer interface
The accelerometer function in this power meter was minutely described in Section 3.1.1
Metering board. The section of the schematic including the accelerometer interface can
be seen in Figure 4-7. In this schematic, the accelerometer is marked U6. The
accelerometer may be used in this power meter for tamper detection (optional only)
instead of the standard button.The accelerometer communicates with the MCU through
IIC data lines, therefore external pull-ups R60 and R61 on the SDA and SCL lines are
required. There is also the possibility of placing the accelerometer outside of the metering
board, like the daughter card thanks to the IIC header J4. This daughter card may be
placed on the inner side of the case cover for a better detection of tamper events.
1
+3.3V
5
3
1
J4
6
4
2
3
2
BAT54CLT1
HDR 2X3
SCL
SDA
/INT
D16
V_BAT
GND
10
9
C44 C45
8
10UF 0.1UF 7
6
R61
1.0K R60
1.0K GND
U6
NC2 RESERVED
DVDD
NC1
DVSS
AVDD
SDA
AVSS
SCL
INT
MMA7660FC
1
2
3
4
5
C46
C47
10UF
0.1UF
GND
Figure 4-7. Accelerometer interface part of the metering board
4.3.8 IIC interface
The IIC interface is used for joining the accelerometer (Section 4.3.7 Accelerometer
interface), and the 1322x-LPN Daughter Card. This daughter card is used primarily for
RF/ZigBee communication, more often then the 1320x-RFC daughter card is used. The
1322x-LPN board is connected via a thin flat cable directly to the 6-pin header J4 of the
metering board and also to the RESET1 push-button of the metering board. A schematic
of the connection between the metering engine and daughter card can be seen in Figure
4-8.
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Chapter 4 Hardware Design of the Metering Board
1322x-LPN
1
I2C_SDA 3
5
7
9
11
J1
Metering board
+3.3V
5
3
1
2
4 I2C_SCL
6
8
10
12
J4
6
4
2
HDR 2X3
GND
90122-12
BC1
GND
2
-
2xAAA Cells
1 +3.3V
+
2468
J17
1
2
TSM-102-01-L-SV
6
RESET1
1
5
2
4
3
P12S1LZ
Figure 4-8. Interface between 1322x-LPN and the metering board
4.4 Signal conditioning
In regards to various signal conditioning part configurations, there are also various power
meter configurations. These configurations depend not only on the analog parts, but also
on digital configurations. There are three power meter configurations differentiated in
regards to the current signal conditioning section:
• Full configuration with both a CT (1 gain or 2 gains) and a shunt resistor (2 gains)
current measurement. For sensor connections to the board see Figure 4-9, for a
schematic view see Figure A-1, and Figure A-2. For layout views see Figure B-1 and
Figure B-2, and for the BOM see Table C-1.
• Low-cost configuration with a shunt resistor (2 gains) current measurement. For
sensor connection to the board see Figure 4-10, for a schematic view see Figure A-3,
and Figure A-4, for layouts views see Figure B-5 and Figure B-6, and for the BOM
see Table C-4.
• Low-cost configuration with a CT (1 gain) current measurement. For sensor
connection to the board see Figure 4-11, for a schematic view see Figure A-3 and
Figure A-5, for layouts views see Figure B-3 and Figure B-4, and for the BOM see
Table C-3.
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Signal conditioning
L_inp
L_out
LOAD
N_inp
N_out
Figure 4-9. Shunt and CT current measurement connection
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Chapter 4 Hardware Design of the Metering Board
L_inp
L_out
LOAD
N
Figure 4-10. Shunt current measurement connection
L_inp
L_out
LOAD
N
Figure 4-11. CT current measurement connection
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Signal conditioning
Apart from these three basic configurations, others may be constructed by adding or
disconnecting some digital parts of the power meter configuration, for example the
infrared or OC communication. Be careful, some parts mainly in the digital area are vital
(MCU core, RS232 communication, and so on).
4.4.1 Voltage measurement
There is a simple voltage divider used for the line voltage measurement in Figure 4-12. It
is a basic and key part of each configuration of the power meter. In the basic block
diagram (see Figure 3-1) there is a voltage divider, based on two simple resistors. In a
practical implementation it is better to design this divider from several resistors
connected serially due to a power-loss spread. One part of this total resistor consists of
R32, R33, R34, and R57, the second part consists of resistor R36. The basic voltage
divider described produces a sine voltage signal around ground. This is not acceptable for
the ADC, because all voltage signals connected to it must be above ground (single-ended
configuration). Therefore, a further voltage divider that raises the signals is added to the
connection. This second divider is made from the R29||R30 combination and from the
R36 (a part of the mains divider). The ratio of this second divider allows having a voltage
on the ADC input from 0 V to 1.2 V (Vref). The sine voltage signal from the mains is
then shifted to Vref/2, that is 0.6 V approximately (voltage at VLINE, see Figure 4-12).
VDDA
TP13
R29
100k
N_IN
R57
220K
R32
220K
R33
100k
R34
47k
R30
4.7K
VLINE
R35
47
V_OUT
V_OUT
1.2V +/-0.6V
1k
R36
GNDA
C30
1000pF
LPF CUTOFF 3.4MHz
GNDA
Figure 4-12. Voltage signal conditioning part schematic
Finally, there is a simple RC low-pass filter (R35+C30) at the end of the voltage divider.
The cut-off frequency for that is set to 3.4 MHz according to this relation:
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4.4.2 DC Bias circuit
This circuit is used for raising the voltage signal levels to about Vref/2 in the current
measurement. This is necessary for converting the input signal levels from differential to
a single-ended configuration, required by the ADC. Its function is the same as the
function of the voltage divider R29||R30 plus the R36 in the voltage measurement section
(see Section 4.4.1Voltage measurement). In comparison to that voltage divider, higher
output loading is required because of using this connection in several parts of the current
measurement sections (see below). Therefore, an operational amplifier U7, working as a
voltage follower, is used for that. This amplifier extends loading of the basic voltage
divider (R21, R56), that produces a DC bias offset of 0.6 V, for using in other parts of the
current measurement sections. The part of the schematic including DC bias circuit is in
Figure 4-13.
R21
1.8K
VDDA
8
3
+
2
GNDA
-
C25
1UF
GNDA
1
DC_BIAS
0.6V
DC_BIAS
MC33502DG
4
R56
390
TP11
U7A
GNDA
Figure 4-13. DC Bias circuit schematic
4.4.3 Shunt resistor current measurement
Because there is a very small voltage drop at the shunt resistor, external amplifiers must
be presented in this part of the connection. Finally, there are two operational amplifiers
used and housed in one package U3 (see Figure 4-14) and some feedback resistors for the
correct function.The first gain stage is made from one half of U3 and resistors, R22, R24,
R25, and R28. For maintaining a good signal stability in this gain stage at higher
frequencies, there is a filter C23 with a small capacity value. This first gain stage works
as a differential amplifier for amplifying higher levels of input signals, and as a preamplifier for the next gain stage, with this gain:
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Signal conditioning
The second stage of the signal conditioning for current measurement is made from the
second half part of the operational amplifier U3 and as usual with the cooperation of a
resistive feedback network (R23, R26) and input bias-adjusting resistor R31. The
capacitor (filter) C27 has the same function as filter C23 in the first gain stage, for
maintaining the signal stability.
NOTE
The second gain stage works in co-operation with the feedback
resistors as an inverting amplifier and because of this, it inverts
the phase of the input signal. Between the first and the second
gain stage there is 180 degree phase shift.
The second gain stage is primarily used for amplifying low levels of input current signals
with this gain ratio:
Between both of these gain stages, there is an isolated capacitor C28, which is used for
cutting off the DC offset. Therefore, the DC offset from the first gain stage is 0.6 V. Both
of these gain stages also have their own RC low-pass filter and similarly to the voltage
measurement (see the previous chapter) are adjusted to 3.4 MHz, approximately (f3db):
NOTE
Filter capacitors (C24, C29) must always be placed as close as
possible to the ADC inputs (layouts in the Appendix section).
This requirement is also valid for filter C30 in the voltage
section. Notice that all the signal levels in this section are raised
above Vref/2 (0.6 V), because of the DC bias circuit.
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TP10
R20
C23
SHUNT_LO
10 PF
R22
47k
LINE_IN
4
3
U3A
MC33502DG
10UF
R26
4.7K
C27
10 PF
R23
100k
6
5
TP12
R27
U3B
SHUNT_HI
7
C29
47
1.2V +/-0.6V
1000pF
MC33502DG
8
+
47k
R28
1
C28
SHUNT_LO
1.2V +/-0.6V
+
Shunt 150uOhm
GNDA
2
R24
1.8K
R25
1.8K
GNDA
LPF CUTOFF 3.4MHz
-
LINE_OUT
C24
1000pF
-
47
VDDA
DC_BIAS
0.6V
R31
100k
GNDA
LPF CUTOFF 3.4MHz
Figure 4-14. Shunt resistor signal conditioning part schematic
4.4.4 CT current measurement
A current measurement through the CT sensor works in two modes:
• Basic (low-cost) mode without an external OpAmp — One-gained measurement
• Full-configuration mode with four OpAmps — Two-gained measurement
The basic component in both of these modes is a burden resistor(s) R40||R45. Other
circuits are not needed for adjustment of the voltage drop on the burden resistor up to the
Vref voltage level (for maximum input current). In fact, only two balancing resistors are
used, R42 and R48, which are connected from its midpoint to the DC bias voltage level
made by the DC bias circuit (see Section 4.4.2 DC Bias circuit). The reason for this, is
the same as in the previous measurement section, for shifting the voltage level above
Vref/2 (0.6 V). For the basic (low-cost) configuration an RC low-pass filter which consist
of two resistors R44, R49, and capacitor C35 are still only needed. The output signals
from this filter (CT_I1+, CT_I1-) are fully-differential in comparison to the shunt resistor
current measurement. Finally, for proper activation of the basic CT current measurement
mode to bypass the first gain stage around U4 operational amplifier is still needed. For
doing this, the jumpers J10 and J13 must be set to position 1–2. Both of these jumpers are
not original components. They are made as small tin SMD shapes on the printed circuit
board. For a basic CT current measurement only a few passive components in this section
are needed, therefore it is called low-cost configuration. It has only one gain set by the
value of burden resistors R40||R45 (see Figure 4-15).
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Signal conditioning
TP14
J10 3 PAD JUMPER
A
2
CT_IN+
1
CT_IN-
J11
R45 R40
39 39
3
R44
DC_BIAS
0.6V
1
J13
CT_I1+
C35
1000pF
R49
1.8K
R48
CT= 1:2500
1.2V +0.6V
47
47
3
B
1.8K
R42
2
CON_2_TB
2
1
TP16
CT_I11.2V -0.6V
TP18
LPF CUTOFF 1.7MHz
TP19
3 PAD JUMPER
Figure 4-15. CT signal conditioning part schematic in low-cost configuration
A full-configuration mode in the case of CT current measurement means a two-gained
input current measurements, similar to current measurement via a shunt resistor (see
Section 4.4.3 Shunt resistor current measurement). A schematic for this configuration can
be seen in Figure 4-16. For proper activation of this mode, jumpers J10 and J13 must be
switched to position 2-3. The full-configuration mode is done by two independent
cascaded sections with instrumentation amplifiers. Each instrumentation amplifier section
is created by two simple operational amplifiers housed in one package. A total of four
OpAmp are used (two IC). The instrumentation amplifier is a type of differential
amplifier with a low DC offset, low drift, high open-loop gain, high CMRR, and high
input impedances. The first instrumentation amplifier section is made from OpAmp U4
and the resistive feedback network (R38, R46, and R54) which gives this gain:
Although the gain ratio of this first stage is set to 17.7 the ohm value of the input burden
resistor R40||R45 must be adequately decreased in this case (approximately 18 x). Filters
C32 and C42 connected in parallel to the feedback resistors are used only for maintaining
the signal stability (against the signal oscillation). Resistors R41 and R51 are used only
for input bias current adjustment and their values are not critical.
The second instrumentation amplifier section consists of the OpAmp U5 and a resistive
feedback network (R37, R47, R55) which gives this gain:
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J10 3 PAD JUMPER
3
1
10 PF
R38
100k
VDDA
VDDA
10K
A
CT_IN+
1
CT_IN-
R45 R40
39 39
J11
DC_BIAS
0.6V
1.8K
R48
CT= 1:2500
R46
12k
R44
MC33502DG
47
GNDA
5
U4B
7
47
C42
+
U5A
-
R47
12k
C35
1000pF
CT_I11.2V -0.6V
R43
1.2V +0.6V
CT_I2+
47
C33
1000pF
GNDA
6
5
U5B
7
R52
1.2V -0.6V
CT_I2-
47
MC33502DG
10K
R54
100k
1
MC33502DG
CT_I1+
TP18 R53
MC33502DG
2
1.2V +0.6V
R49
6
R51
10K
TP19
-
4
2
10K
+
B
1.8K
R42
3
TP16
1
-
CON_2_TB
2
+
U4A
8
3
TP15
4
8
R41
+
TP14
R37
100k
R39
-
10 PF
2
C31
C32
R55
100k
TP17
LPF CUTOFF=1.7MHz
C43
3
1
J13
2
10 PF
10 PF
3 PAD JUMPER
Figure 4-16. CT signal conditioning part schematic in full configuration
Others components, such as filters C31, C43 and resistors R39, and R53 perform the
same function as in the first gain stage.
The simple RC low-pass filters terminate both of these measurement sections. The cut-off
frequency is computed as:
NOTE
Filters C35 and C33 must be placed as close as possible to the
MCU (U1) where the ADC is (see layouts in the Appendix
section). The first gain stage is used for amplifying higher
levels of input current signals and as a pre-amplifier for the
second gain stage, which is used for amplifying lower levels of
input current signals.
4.4.5 Input protection
An input protection section is an important part of the power meter—it protects the
integrated circuits against overvoltages and spikes that sometimes occur in the power
line. A high-energy spikes are absorbed primarily by varistor RS1. A low-energy spike is
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Signal conditioning
absorbed by diodes D10–D14 (see Figure 4-17). All of these diodes do not allow an input
voltage in each measurement input part to be higher than 3.3 V and lower than 0 V (in
respect to the voltage drop on the diode).
D10
1
3
GNDA
VDDA
VLINE
2
BAV99LT1
LINE_IN
D11
1
3
LINE_OUT
2
BAV99LT1
LINE_OUT
D12
1
3
LINE_IN
2
BAV99LT1
D13
1
GNDA
VDDA
3
CT_IN+
3
CT_IN-
2
BAV99LT1
D14
1
GNDA
VDDA
2
BAV99LT1
Figure 4-17. Schematic of input protection diodes
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Chapter 5
Application Set-Up
5.1 Setting-up the demo hardware
The following section is focused on setting-up the metering demo hardware. For better
orientation in the power meter demo see Figure 3-9.
•
•
•
•
•
Connect the power meter plug directly to the power line
Green power LED turns-on at this time
Connect an external load to the single phase outlet
LCD shows the RMS line current in Amp after a power-on (default state)
User can also see other values on the LCD by pressing push-buttons SW1 or SW2.
These values include:
• Active energy in kWh
• Reactive energy in kVArh — Value with R symbol on the left side of the LCD
• Actual time — Format is, hour, min, sec, plus the TIME symbol
• Actual date — Format is, day of week, day, month, year plus the DATE symbol
• Line frequency — Is the value with Hz symbol on the right side of the LCD
• RMS line voltage — Value with U symbol on the left side of the LCD, plus the
volts symbol
• RMS line current — Value with I symbol on the left side of the LCD, plus the
Amps symbol
• Active power — Value with W symbol on the right side of the LCD
• Reactive power — Value with Var symbol on the right side of the LCD
• Apparent power — Value with VA symbol on the right side of the LCD
• Power factor — Value with PF symbol on the left side of the LCD
• Both the energies (active and reactive) are saved in non-volatile memory. These
energies remain in the memory after resetting the power meter. For clearing energy
counters, you must push both of the SW buttons during reset.
• When you push only the SW1 button during any soft or hard reset, the LCD shows
the actual version of the internal software.
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
57
Setting-up the software demo
• Press the Tamper button for a tampering simulation. There will be a Tampering text
on the LCD after pressing this button and a fire symbol on the LCD appears. The fire
symbol remains on the LCD after any reset, because this information is saved in the
non-volatile memory. For clearing the tamper status you must push both of the SW
buttons during any reset (soft or hard reset).
NOTE
Together with the tamper status, both energy counters are
also erased.
• A soft HW reset of the power meter is done by the Reset push-button, a hard HW
reset is executed by disconnecting the power meter plug from the power line
network.
• Energy LEDs are flashing simultaneously with internal energy counters.
• 3 V battery is used for the RTC function and the data storage (tamper plus energy
counters).
• RS232 plug is used for code flashing and for FreeMASTER data visualization and
calibration
5.2 Setting-up the software demo
The following section is focused on setting-up the metering demo software.
5.2.1 FreeMASTER data visualization
For FreeMASTER data visualization the RS232 cable between the power meter and the
PC must first be connected. The FreeMASTER visualization script is the software for
remote visualization and remote settings of the power meter up via an RS232 cable. This
software runs on the PC that connects to the power meter via an RS232 cable. FreeMaster
visualization script is the application that runs under FreeMASTER software.
FreeMASTER software is one of the off-chip drivers which supports communication
between the target microcontroller and a PC. This tool allows the programmer to
remotely control an application using a user-friendly graphical environment running on a
PC. It also provides the ability to view some real-time application variables in both
textual and graphical form. FreeMASTER software runs under Windows 98, 2000, or
XP. It is a versatile tool to be used for multipurpose algorithms and applications. It
provides a lot of excellent features, including:
• Real-time debugging
• Diagnostic and a visualisation tool
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
58
Freescale Semiconductor, Inc.
Chapter 5 Application Set-Up
• Demonstration tool
• Education tool
Before running a visualization script, FreeMASTER software must be installed on your
PC. After, a FreeMASTER visualization script may be started after double-clicking on
the EM256kWh.pmp file in the current directory (EM256kWh project). Following this, a
visualization script will appear on your PC (see Figure 5-1).
You must now set the proper serial communication port and speed in the menu Project/
Option (see Figure 5-2). To do this, you must click on the Start/Stop Communication
button. After, you must set the proper Project.abs project file in the menu Project/Option/
MAPfiles (see Figure 5-3). This file is accessible in the Bin directory of the EM256kWh
project. If all previous settings are correctly done, the FreeMASTER visualization script
for the power meter is now running. At this point you can see the voltage and current
diagram in the time domain and in the frequency domain (in FFT window). You may also
see other variables in a text format like frequency, VRMS, IRMS, and so on.
Figure 5-1. FreeMASTER visualization script (GUI)
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
59
Setting-up the software demo
Figure 5-2. FreeMASTER communication port setting
Figure 5-3. FreeMASTER project file setting
5.2.2 ZigBee communication
ZigBee communication is only optional and is not implemented in every power meter
demo. There is a 2.4 GHz 1322x daughter card inside the power meter. The ZigBee
module and the power meter are connected through the IIC. For joining the power meter
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
60
Freescale Semiconductor, Inc.
Chapter 5 Application Set-Up
to the ZigBee network, you will need the 1322x-SRB module, this is like a ZigBee
coordinator (see Figure 5-4). The power meter can now easily become part of the smart
grid.
Figure 5-4. 1322x-SRB as ZigBee Coordinator
Here is a standard communication procedure for joining the power meter to smart grid:
• Install the latest version of the BeeKit from the Freescale web page. There is also a
ZeD monitor and is a separate part of the BeeKit. Use the ZeD monitor for
demonstrating ZigBee communication between the power meter and the PC
• Switch the power meter on and connect some load to the power meter outlet
• Connect the ZigBee coordinator (1322x-SRB) to the PC through a USB cable and
switch the coordinator on. The coordinator must be powered. To do this, plug the AC
adaptor to the coordinator (you may also use the internal battery inside of the
coordinator module), or use a USB power line from the PC side (this is the best
choice). You will have to install the software driver for this equipment after the first
connection of the 1322x-SRB to the PC. The driver is on the CD in directory Drivers
\LuminaryFTDI or alternatively on the FTDI web page
• Push the button SW1 on the coordinator – it is looks up all ZigBee equipment
connected to the ZigBee network at this time. Two red LEDs on the coordinator are
then lit (see Figure 5-4)
• Start the ZeD monitor and then click on the OK button. Before running the ZeD GUI,
the ZigBee coordinator must be connected to the PC through a USB cable.
• At this moment there are several icons of all the devices connected to the ZigBee
network, and only power meter plus the coordinator (see Figure 5-5) in this case. If
there is no icon for the power meter, you must reset the power meter using the reset
button and reset the ZeD GUI using the F5 key. You may also repeat the installation
from point 2 in this case
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
61
Setting-up the software demo
• In the ZeD GUI menu you may open a new window for showing the ZigBee data
transfer. This is in Tools/Start SE Utility Control Panel menu. You must address the
meter by clicking the Add New Household ESP Connection, and then click on the
Connect icon (see Figure 5-6)
• For showing data (only kWh) you must click on the Metering icon and a kWh data
table is now refreshed (every 5 seconds). The most important is the meter report
column, where active energy from the power meter is displayed (see Figure 5-7).
These numbers are in HEX format to 0.0001 kWh resolution, but the kWh-number
on the LCD of the power meter is to 0.001kWh resolution. It is ten times lower then
the numbers in the ZeD GUI. The reason for this is as follows: there are not many
LCD digits for the kWh data displaying in the power meter LCD module.
Figure 5-5. ZeD GUI
Figure 5-6. Add new household ESP connection dialog box
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
62
Freescale Semiconductor, Inc.
Chapter 5 Application Set-Up
Figure 5-7. Metering report in ZeD GUI
5.2.3 Code reprogramming via serial bootloader
There is a developer’s serial bootloader in the power meter that allows in-circuit
reprogramming of the Power Meter MCU using the standard SCI port. A detailed
description of this bootloader is out of content of this design reference manual. It is
described in the application note titled Developer’s Serial Bootloader for M68HC08 and
HCS08 MCUs (document AN2295).
Firstly, you must connect an RS232 cable between the power meter and the PC. Then you
must double-click on file BootLoaderControl.exe in the directory BootLoader. This
program is a GUI for bootloader (see Figure 5-8). In this program you must first select
the correct communication port of the PC, where the RS232 cable is connected. Then you
must open the *.s19 file of the actual code which you want to flash to the MCU of the
power meter. Originally, this file is accessible in the Bin directory of the EM256kWh
project. Finally, you must click on the Bootload icon in the GUI. Then turn the power
meter on (soft or hard reset) and if all the connections are OK, the PC begins to
communicate with the MCU in the power meter. This takes approximately 1 minute.
After flashing, the Reset push-button must be clicked, the MCU program then
automatically runs with a new code.
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
63
Setting-up the software demo
Figure 5-8. Serial bootloader GUI
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
64
Freescale Semiconductor, Inc.
Appendix A
Schematics
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
65
A
B
C
GND
A
GND
L_IN
R5
330
LED_kWh
SJ1
1
5
WP7104LSRD
100PF
0.1UF
GNDA
C6
C5
+3.3VA
1
4
2
GND
10K
R18
TAMPER
+3.3V
32.768KHz
Y1
3
P12S1LZ
TAMPER1
GNDA
4
6
10K
R15
CT_I2SHUNT_LO
SHUNT_HI
V_OUT
2
2
GND
WP7104LSRD
D5
2
1
2 PAD JUMPER
0.1UF
C16
1uH
4
2
+3.3V
1
C4
100PF L2
1
LCD25
LCD26
PTD0/LCD27/KBI2P0
PTD1/LCD28/KBI2P1
PTD2/LCD29/KBI2P2
PTD3/LCD30/KBI2P3
PTD4/LCD31/KBI2P4/TMRCLK1
PTD5/LCD32/KBI2P5/TMRCLK2
PTD6/LCD33/KBI2P6
PTD7/LCD34/KBI2P7
LCD35/CLKOUT
PTF0/LCD36
PTF1/LCD37/EXTRIG
PTF2/LCD38/RX3
PTF3/LCD39/TX3
PTF4/LCD40/AD16
PTF5/LCD41/AD17
PTF6/LCD42/AD18
PTF7/LCD43/AD19
VDDA
VREFH
DADP0
DADM0
AD4
DADP1
U1
DC_BIAS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
0.1UF
C18
0.1UF
C15
0.1UF
GND
C1
0.1UF
C14
GND
C3
47UF
1uH
5
D15
BATTERY
1
3V Battery
GND
BT1
SHUNT_LO
SHUNT_HI
CT_I2+
CT_I2-
LCD25
LCD26
LCD27
LCD28
LCD29
LCD30
LCD31
LCD32
LCD33
LCD34
LCD35
LCD36
LCD37
LCD38
LCD39
LCD40
LCD41
LCD42
LCD43
+3.3VA
VREFH
CT_I1+
CT_I1-
GND
+
L1
1
2
Optical Interface
R59
330
RS1
20S0271
2
V_OUT
DC_BIAS
ANALOG SENSING
N_IN
CT_I2+
CT_I2-
SHUNT_LO
SHUNT_HI
LINE_OUT
LINE_IN
+3.3VA
CT_I1+
CT_I1-
+3.3VA
GNDA
PAGE01
GND
N_IN
2
1
1
2
B
TP3
TP2
R2
330
WP7104LGD
D2
GND
CON_2_TB
A
Q1 J2
MMBTA42
1
2
GNDA
+3.3VA
GND
5.1V
D1
MMSZ5231BT1G
User Interface
LED_kVarh
J9
A
B
CON_2_TB
J6
B
CON_2_TB
GND
R3 1
220
+3.3V
TP4
TP1
WP7104LYD
D4
220
R4
LED_USR
+3.3V
1
D
GND
External isolated
+3.3V, 200mA
switched mode
power supply
CON_2_TB
2
VDDA
2
3
2
1
2
1
2
1
GNDA
B
V_OUT
+3.3V
47UF
+ C7
D3
MMSZ5231BT1G
5.1V
U2
SO
7
2
3
+3.3V
9
GND SPI1_SCK
SPI1_MOSI
RF_ATTN
RF_RESET
SPI1_MISO
EXP
HOLD
MRAM
WP
VSS
CS
8
VDD
SCK
SI
MR25H10CDC 4
+3.3V
3
1
6
5
GND
V_OUT
1UF
MCF51EM256
PTE7/LCD5
PTC7/LCD4
PTC6/LCD3/CMP2P5
PTC5/LCD2/CMP1P5
PTC4/LCD1/CMP2O
PTC3/LCD0/CMP1O
BKGD/MS/PTC2
PTC1/KBI1P7/XTAL2/TX3
PTC0/KBI1P6/EXTAL2/RX3
RESET
PTB7/RGPIO15/KBI1P5/TMRCLK2/AD15
PTB6/RGPIO14/KBI1P4/TMRCLK1/AD14
PTE6/SSB3/TX2
PTE5/SCLK3
PTE4/MISO3/MOSI3
PTE3/MOSI3/MISO3
PTB5/RGPIO13/SDA/CMP2P4
PTB4/RGPIO12/SCL/CMP2P3
PTB3/RGPIO11/KBI1P3/CMP2P2/TX1
PTB2/RGPIO10/KBI1P2/CMP2P1/RX1
VSS
VDD
PTB1/RGPIO9/KBI1P1/SSB3/TX2
PTB0/RGPIO8/KBI1P0/CMP1P1/RX2
PTE2/CMP1P2
C49
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
3
0.1UF
C22
+3.3V
10K
R11
LCD12
LCD13
LCD14
LCD15
LCD16
LCD17
LCD18
LCD19
LCD20
LCD21
LCD22
LCD23
LCD24
LCD25
LCD26
LCD27
LCD43
LCD42
LCD41
LCD40
LCD39
LCD38
IR_TX
CON_2X20
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
SPI1_MOSI
RF_CE
2
+3.3V
330
R14
TP9
+3.3V
R6
330
4
1
2
GND
TP6
3
R9
1.0K
1
2
2
ISO3
SFH6106-4
SFH6106-4
1
GND
GND
GNDA
GNDA
C45
ISO2
4
3
U6
1
2
3
4
5
2
D7
D6
RXD
TXD
DTR
GND
1
3
5
7
9
2
4
6
8
10
CON_2X5
J5
RS232
Interface
A
J7
B
CON_2_TB
1
Energy output
pulse interface
EOC_OE 1
EOC_OC 2
RS232 isolated
(Half Duplex, max 19200 Bd)
D8
R13
470
2.2UF
C19
R7
4.7K
(+12V)
RTS
GND
C47
0.1UF
C46
10UF
GNDA
Isolation barrier
MMA7660FC
NC2 RESERVED
DVDD
NC1
DVSS
AVDD
SDA
AVSS
SCL
INT
MMSD4148T1G
1 1
2
4
3
GND
10
9
8
7
6
Accelerometer Interface
10UF 0.1UF
C44
GNDA
C12
0.1UF
VREFO
C11
0.1UF
VREFH
C48
10UF
+3.3VA
C10
0.1UF
+3.3VA
C9
10UF
+3.3V
Place as close as possible to U1!
C8
0.1UF
+3.3V
All caps in 0805 package
Filters for MCU
R61
1.0K R60
1.0K
3
SFH6106-4
V_BAT
BAT54CLT1
ISO1
GND
6
4
2
+3.3V
HDR 2X3
TSAL4400
D9
R8
680.0
GND
RF_RTXEN
IRQ
+3.3V
GND
1
D16
4
P12S1LZ
5
3
6
2
J4
TP7
TP5
SCL
5
/INT
SDA 3
1
GND
100PF
P12S1LZ
SW2
3
1
4
2
100PF
GND
5
1
6
4
3
P12S1LZ
SW1
5
6
+3.3V
2
1
R1
4.7K
RESET1
3 Buttons
C13
GND
SDA
SCL
RS232_TXD
RS232_RXD
EOC_PULSE
OP506B
Q3
+3.3V
RF/ZigBee Interface
GND
J8
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
RF_CE
RF_RTXEN
IRQ
0.1UF
C21
IR_RX
+3.3V
R58
10K
GND
RESET
+3.3V
R10
22K
R12
1.0K
6
4
2
HDR 2X3
GND
5
3
1
J3
2
0.1UF
C2
SW2 C17
SW1
RESET
Infrared interface
TP8
RF_RESET
GND
100PF
C20
IR_TX
IR_RX
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
BDM
Interface
GD-3980P
FP8
FP9
FP10
FP11
FP12
FP13
FP14
FP15
FP16
FP17
FP18
FP19
FP20
FP21
FP22
FP23
FP39
FP38
FP37
FP36
FP35
FP34
LCD5
LCD4
LCD3
LCD2
LCD1
LCD0
BKGD
LED_USR
/INT
RESET
SW1
SW2
VCCPRESENT
LED_kVarh
LED_kWh
EOC_PULSE
SDA
SCL
RS232_TXD
RS232_RXD
GND +3.3V
BP0
BP1
BP2
BP3
FP0
FP1
FP2
FP3
FP4
FP5
FP6
FP7
FP24
FP25
FP26
FP27
FP28
FP29
FP30
FP31
FP32
FP33
LCD1
GND
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
Display
LCD0
LCD1
LCD2
LCD3
LCD4
LCD5
LCD6
LCD7
LCD8
LCD9
LCD10
LCD11
LCD28
LCD29
LCD30
LCD31
LCD32
LCD33
LCD34
LCD35
LCD36
LCD37
V_OUT
A
DC_BIAS
1
2
1
5
2
DADM1
AD5
DADP2
DADM2
AD6
DADP3
DADM3
AD7
VREFO
VREFL
VSSA
EXTAL1
XTAL1
VBAT
TAMPER
PTA0/RGPIO0/IRQ/CLKOUT
PTE0/CMP1O/AD8
PTE1/CMP1P4/AD9
PTA1/RGPIO1/MOSI1
PTA2/RGPIO2/MISO1/AD10
VREFO
1
2
2
1
LCD24
LCD23
LCD22
LCD21
LCD20
LCD19
LCD18
LCD17
LCD16
LCD15
LCD14
LCD13
LCD12
LCD11
LCD10
LCD9
LCD8
LCD7
LCD6
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
MMSD4148T1G
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
EXTAL1
XTAL1
VBAT
TAMPER
IRQ
RF_RESET
RF_ATTN
SPI1_MOSI
SPI1_MISO
2
1
VCAP1
VCAP2
VLL1
VLL2
VLL3
VSS
LCD24
LCD23
LCD22
LCD21
LCD20
LCD19
LCD18
LCD17
LCD16
LCD15
LCD14
LCD13
LCD12
LCD11
LCD10
LCD9/SSB2
LCD8/SCLK2
LCD7/MISO2
LCD6/MOSI2
PTA3/RGPIO3/SCLK1
PTA4/RGPIO4/SSB1
PTA5/RGPIO5/TPMCH0/AD11
PTA6/RGPIO6/TPMCH1/AD12
PTA7/RGPIO7/TPMCLK/CMP1P3/AD13
46
47
48
49
50
SPI1_SCK
SPI1_SS
RF_RTXEN
RF_CE
MMSD4148T1G
66
+
J1
A
B
C
D
Schematics for Full Configuration of the Metering Board
A.1 Schematics for Full Configuration of the Metering Board
Figure A-1. Full digital configuration of the metering board schematic
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
A
B
C
D
R32
220K
2
3
GNDA
-
R33
100k
MC33502DG
1
U7A
+
8
4
A
B
5
CT_IN-
1
TP19
CT_IN+
2
CT= 1:2500
RC= 0.8mV/A
J11
CON_2_TB
TP14
R45 R40
39 39
1.8K
R42
10K
R51
10K
R41
R35
47
10 PF
C42
R46
12k
10 PF
C32
1k
R36
GNDA
VLINE
R30
4.7K
VDDA
DC_BIAS
G1 = (1+2*R38/R46)
G1 = 17.7
R54 = R46
1.8K
R48
R29
100k
DC_BIAS
0.6V
R34
47k
TP11
DC_BIAS
0.6V
CURRENT SENSING USING CURRENT
TRANSFORMER OR ROGOWSKI COIL
Voltage measurement
N_IN
C25
1UF
GNDA
R57
220K
GNDA
R56
390
VDDA
5
6
2
3
-
+
U4A
U4B
1
VDDA
R54
100k
4
47
R49
Gtotal=312
3 PAD JUMPER
J13
MC33502DG
7
GNDA
47
R44
J10 3 PAD JUMPER
MC33502DG
R38
100k
GNDA
V_OUT
1.2V +/-0.6V
C30
1000pF
LPF CUTOFF 3.4MHz
V_OUT
TP13
2
2
R21
1.8K
4
3
3
5
8
+
-
4
1
1
LINE_OUT
10K
R39
CT_I1-
CT_I1+
TP18
R47
12k
-
U5B
3
2
1
VDDA
MC33502DG
U3A
GNDA
10 PF
R22
47k
C23
10 PF
R55
100k
MC33502DG
7
GNDA
MC33502DG
1
VDDA
3
C24
1000pF
10UF
C28
R31
100k
4.7K
R26
TP17
TP15
CT_I2-
1.2V -0.6V
C33
1000pF
CT_I2+
1.2V +0.6V
U3B
R23
100k
GNDA
47
R27
GNDA
VDDA
100PF
GNDA
BAV99LT1
2
BAV99LT1
D14
1
2
BAV99LT1
D13
1
2
D12
1
BAV99LT1
2
D11
1
BAV99LT1
2
GNDA
0.1UF
C40
VDDA
100PF
C41
GNDA
0.1UF
C50
VDDA
Input protection
VDDA
GNDA
VDDA
GNDA
LINE_IN
LINE_OUT
LINE_OUT
LINE_IN
VDDA
D10
1
1
CT_IN-
CT_IN+
VLINE
100PF
C51
3
3
3
3
3
2
1
Note:
C24,C29,C30,C33,C35 are low-pass filter capacitors.
Place it as close as possible to ADC (U1) !
GNDA
0.1UF
C38
VDDA
Bypass capacitors
100PF
0.1UF
GNDA
C37
C36
VDDA
C39
1.2V +/-0.6V
SHUNT_HI
LPF CUTOFF 3.4MHz
GNDA
1000pF
C29
TP12
Supply connection
MC33502DG
7
VDDA
SHUNT_LO
1.2V +/-0.6V
2
G2=R23/R26
G2=21.3
5
6
10 PF
C27
SHUNT_LO
LPF CUTOFF frequency
f3dB = 1/(2PI*(R43+R52)*C33)
f3dB = 1.7MHz
47
R52
47
R43
TP10
GNDA
LPF CUTOFF 3.4MHz
47
R20
Gtotal=556
G1=R22/R24=R28/R25
G1=26.1
47k
R28
R37
100k
+
U5A
C43
5
6
2
3
10 PF
C31
R24
1.8K
R25
1.8K
G2 = (1+2*R37/R47)
G2 = 17.7
R55 = R47
10K
R53
1.2V -0.6V
C35
1000pF
DC_BIAS
0.6V
LINE_IN
Shunt 150uOhm
1.2V +0.6V
TP16
3
CURRENT SENSING USING SHUNT
8
+
-
4
4
+
-
8
+
Freescale Semiconductor, Inc.
-
DC bias voltage 0.6 V
A
B
C
D
Appendix A Schematics
Figure A-2. Full analog schematic of the metering board
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
67
A
B
C
D
GND
A
5
WP7104LSRD
GNDA
0.1UF
C5
+3.3VA
Y1
1
4
2
GND
10K
R18
TAMPER
+3.3V
32.768KHz
3
P12S1LZ
1
4
+3.3V
TAMPER1
10K
R15
GNDA
WP7104LSRD
D5
2
1
6
V_OUT
CT_I2SHUNT_LO
SHUNT_HI
DC_BIAS
2
2
GND
2
Optical Interface
R5
330
LED_kWh
C16
0.1UF
1uH
LCD25
LCD26
PTD0/LCD27/KBI2P0
PTD1/LCD28/KBI2P1
PTD2/LCD29/KBI2P2
PTD3/LCD30/KBI2P3
PTD4/LCD31/KBI2P4/TMRCLK1
PTD5/LCD32/KBI2P5/TMRCLK2
PTD6/LCD33/KBI2P6
PTD7/LCD34/KBI2P7
LCD35/CLKOUT
PTF0/LCD36
PTF1/LCD37/EXTRIG
PTF2/LCD38/RX3
PTF3/LCD39/TX3
PTF4/LCD40/AD16
PTF5/LCD41/AD17
PTF6/LCD42/AD18
PTF7/LCD43/AD19
VDDA
VREFH
DADP0
DADM0
AD4
DADP1
U1
1
C4
100PF L2
1
4
5
D15
BATTERY
1
3V Battery
GND
BT1
SHUNT_LO
SHUNT_HI
CT_I2+
CT_I2-
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
C18
0.1UF
C15
0.1UF
0.1UF
GND
C1
0.1UF
C14
GND
C3
47UF
1uH
1
2
RS1
20S0271
2
V_OUT
DC_BIAS
ANALOG SENSING
N_IN
CT_I2+
CT_I2-
SHUNT_LO
SHUNT_HI
LINE_OUT
LINE_IN
CT_I1+
CT_I1-
+
GND
LCD25
LCD26
LCD27
LCD28
LCD29
LCD30
LCD31
LCD32
LCD33
LCD34
LCD35
LCD36
LCD37
LCD38
LCD39
LCD40
LCD41
LCD42
LCD43
+3.3VA
VREFH
CT_I1+
CT_I1-
TP3
TP2
R2
330
WP7104LGD
D2
GND
+3.3VA
GNDA
+3.3VA
GND
5.1V
D1
MMSZ5231BT1G
+3.3VA
GNDA
PAGE01
TP4
TP1
GND
L_IN
1
R59
330
A
N_IN
2
1
LED_kVarh
J9
B
CON_2_TB
J6
B
2
GND
CON_2_TB
+3.3V
External isolated
+3.3V, 200mA
switched mode
power supply
CON_2_TB
VDDA
2
GNDA
1
2
1
V_OUT
L1
VREFO
B
DC_BIAS
+3.3V
100PF
C6
47UF
+ C7
D3
MMSZ5231BT1G
5.1V
GND
MCF51EM256
V_OUT
1UF
PTE7/LCD5
PTC7/LCD4
PTC6/LCD3/CMP2P5
PTC5/LCD2/CMP1P5
PTC4/LCD1/CMP2O
PTC3/LCD0/CMP1O
BKGD/MS/PTC2
PTC1/KBI1P7/XTAL2/TX3
PTC0/KBI1P6/EXTAL2/RX3
RESET
PTB7/RGPIO15/KBI1P5/TMRCLK2/AD15
PTB6/RGPIO14/KBI1P4/TMRCLK1/AD14
PTE6/SSB3/TX2
PTE5/SCLK3
PTE4/MISO3/MOSI3
PTE3/MOSI3/MISO3
PTB5/RGPIO13/SDA/CMP2P4
PTB4/RGPIO12/SCL/CMP2P3
PTB3/RGPIO11/KBI1P3/CMP2P2/TX1
PTB2/RGPIO10/KBI1P2/CMP2P1/RX1
VSS
VDD
PTB1/RGPIO9/KBI1P1/SSB3/TX2
PTB0/RGPIO8/KBI1P0/CMP1P1/RX2
PTE2/CMP1P2
C49
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
3
3
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
Display
LCD0
LCD1
LCD2
LCD3
LCD4
LCD5
LCD6
LCD7
LCD8
LCD9
LCD10
LCD11
LCD28
LCD29
LCD30
LCD31
LCD32
LCD33
LCD34
LCD35
LCD36
LCD37
10K
GND
100PF
C20
RS232_TXD
RS232_RXD
GND +3.3V
RESET
SW1
SW2
VCCPRESENT
LED_kVarh
LED_kWh
R11
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
LCD12
LCD13
LCD14
LCD15
LCD16
LCD17
LCD18
LCD19
LCD20
LCD21
LCD22
LCD23
LCD24
LCD25
LCD26
LCD27
LCD43
LCD42
LCD41
LCD40
LCD39
LCD38
5
3
1
6
4
2
R58
10K
HDR 2X3
J3
BDM
Interface
GD-3980P
FP8
FP9
FP10
FP11
FP12
FP13
FP14
FP15
FP16
FP17
FP18
FP19
FP20
FP21
FP22
FP23
FP39
FP38
FP37
FP36
FP35
FP34
LCD5
LCD4
LCD3
LCD2
LCD1
LCD0
BKGD
LED_USR
BP0
BP1
BP2
BP3
FP0
FP1
FP2
FP3
FP4
FP5
FP6
FP7
FP24
FP25
FP26
FP27
FP28
FP29
FP30
FP31
FP32
FP33
LCD1
V_OUT
5
EXTAL1
XTAL1
VBAT
TAMPER
+3.3V
GND
RESET
+3.3V
C2
RS232_TXD
RS232_RXD
2
TP5
GND
100PF
ISO1
+3.3V
4
GND
TP6
3
R9
1.0K
1
2
SFH6106-4
SFH6106-4
4
R6
330
5
3
6
2
P12S1LZ
P12S1LZ
SW2
3
1
4
2
100PF
GND
5
1
6
4
3
P12S1LZ
SW1
5
6
+3.3V
2
1
R1
4.7K
RESET1
3 Buttons
C13
GND
0.1UF
SW2 C17
SW1
RESET
2
1
GND
GND
ISO2
GNDA
GNDA
2
D7
D6
RXD
TXD
DTR
GND
1
3
5
7
9
2
4
6
8
10
CON_2X5
J5
RS232
Interface
RTS
1
RS232 isolated
(Half Duplex, max 19200 Bd)
D8
R13
470
2.2UF
C19
R7
4.7K
(+12V)
MMSD4148T1G
1 1
2
4
3
GNDA
Isolation barrier
GNDA
C12
0.1UF
VREFO
C11
0.1UF
VREFH
C48
10UF
+3.3VA
C10
0.1UF
+3.3VA
C9
10UF
+3.3V
Place as close as possible to U1!
C8
0.1UF
+3.3V
All caps in 0805 package
Filters for MCU
2
1
A
1
2
DADM1
AD5
DADP2
DADM2
AD6
DADP3
DADM3
AD7
VREFO
VREFL
VSSA
EXTAL1
XTAL1
VBAT
TAMPER
PTA0/RGPIO0/IRQ/CLKOUT
PTE0/CMP1O/AD8
PTE1/CMP1P4/AD9
PTA1/RGPIO1/MOSI1
PTA2/RGPIO2/MISO1/AD10
2
1
LCD24
LCD23
LCD22
LCD21
LCD20
LCD19
LCD18
LCD17
LCD16
LCD15
LCD14
LCD13
LCD12
LCD11
LCD10
LCD9
LCD8
LCD7
LCD6
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
MMSD4148T1G
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
VCAP1
VCAP2
VLL1
VLL2
VLL3
VSS
LCD24
LCD23
LCD22
LCD21
LCD20
LCD19
LCD18
LCD17
LCD16
LCD15
LCD14
LCD13
LCD12
LCD11
LCD10
LCD9/SSB2
LCD8/SCLK2
LCD7/MISO2
LCD6/MOSI2
PTA3/RGPIO3/SCLK1
PTA4/RGPIO4/SSB1
PTA5/RGPIO5/TPMCH0/AD11
PTA6/RGPIO6/TPMCH1/AD12
PTA7/RGPIO7/TPMCLK/CMP1P3/AD13
46
47
48
49
50
MMSD4148T1G
68
+
J1
A
B
C
D
Schematics for Low-Cost Configurations of the Metering Board
A.2 Schematics for Low-Cost Configurations of the Metering
Board
Figure A-3. Low-cost configuration of the digital schematic of the metering board
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
A
B
C
1UF
C25
GNDA
2
3
2
LINE_IN
5
1
3
3
3
VLINE
MC33502DG
Input protection
BAV99LT1
D12
1
BAV99LT1
2
D11
1
-
+
U7A
GNDA
BAV99LT1
2
D10
1
VDDA
LINE_OUT
LINE_OUT
LINE_IN
VDDA
GNDA
GNDA
R56
390
R21
1.8K
4
D
8
DC bias voltage 0.6 V
TP11
GNDA
VDDA
100PF
0.1UF
4
GNDA
0.1UF
C50
VDDA
100PF
C51
DC_BIAS
0.6V
LINE_IN
Shunt 150uOhm
LINE_OUT
Bypass capacitors
C41
GNDA
3
R24
1.8K
R25
1.8K
VDDA
MC33502DG
1
GNDA
R57
220K
R32
220K
3
Voltage measurement
N_IN
U3A
TP10
10UF
C28
R31
100k
4.7K
R26
R33
100k
2
R34
47k
SHUNT_LO
U3B
R23
100k
R29
100k
1k
R36
GNDA
VLINE
R30
4.7K
VDDA
R35
47
MC33502DG
7
1.2V +/-0.6V
G2=R23/R26
G2=21.3
5
6
10 PF
C27
SHUNT_LO
C24
1000pF
2
GNDA
LPF CUTOFF 3.4MHz
47
R20
Gtotal=556
G1=R22/R24=R28/R25
G1=26.1
47k
R28
3
2
C23
10 PF
R22
47k
CURRENT SENSING USING SHUNT
C40
VDDA
Supply connection
GNDA
VDDA
DC_BIAS
0.6V
DC_BIAS
4
4
+
8
+
-
Freescale Semiconductor, Inc.
-
5
GNDA
1000pF
C29
TP12
SHUNT_HI
1.2V +/-0.6V
GNDA
1.2V +/-0.6V
1
C30
1000pF
LPF CUTOFF 3.4MHz
V_OUT
V_OUT
LPF CUTOFF 3.4MHz
TP13
47
R27
1
A
B
C
D
Appendix A Schematics
Figure A-4. Low-cost analog schematic of the metering board with shunt resistor
configuration
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
69
A
B
R32
220K
R33
100k
R34
47k
4
R29
100k
J11
CT_IN-
1
5
TP19
CT_IN+
2
CT= 1:2500
A
B
CON_2_TB
TP14
R45 R40
39 39
1.8K
R48
DC_BIAS
0.6V
1.8K
R42
4
3 PAD JUMPER
J13
47
R49
47
R44
J10 3 PAD JUMPER
TP18
GNDA
3
V_OUT
1.2V +/-0.6V
3
C30
1000pF
LPF CUTOFF 3.4MHz
V_OUT
TP13
LPF CUTOFF 1.7MHz
CT_I1-
1.2V -0.6V
C35
1000pF
R35
47
CT_I1+
1.2V +0.6V
TP16
GNDA
1k
R36
R30
4.7K
VDDA
VLINE
Current sensing using Current Transformer
Voltage measurement
R57
220K
1
1
C
N_IN
2
2
D
3
3
GNDA
VDDA
100PF
C51
2
Bypass capacitors
GNDA
0.1UF
C50
VDDA
Supply connection
GNDA
VDDA
1UF
C25
GNDA
VDDA
GNDA
R56
390
R21
1.8K
2
3
1
MC33502DG
BAV99LT1
2
BAV99LT1
D14
1
2
D13
1
1
1
3
3
3
DC_BIAS
0.6V
BAV99LT1
2
D10
1
TP11
Input protection
VDDA
GNDA
VDDA
GNDA
VDDA
GNDA
GNDA
-
+
U7A
DC bias voltage 0.6 V
2
8
70
4
5
CT_IN-
CT_IN+
VLINE
DC_BIAS
A
B
C
D
Schematics for Low-Cost Configurations of the Metering Board
Figure A-5. Low-cost analog schematic of the metering board with low-cost CT
configuration
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
A
B
C
D
R57
220K
R32
220K
R33
100k
R34
47k
A
1
2
CT= 1:2500
J11
B
CON_2_TB
5
TP19
CT_IN-
CT_IN+
TP14
10K
R51
10K
10 PF
C42
R46
12k
5
6
2
3
-
+
U4A
U4B
4
R54
100k
47
R49
Gtotal=312
3 PAD JUMPER
J13
MC33502DG
7
GNDA
47
R44
J10 3 PAD JUMPER
GNDA
1.2V +/-0.6V
V_OUT
10K
CT_I1-
CT_I1+
10K
R53
3
R56
390
R47
12k
-
U5B
1
VDDA
VDDA
2
3
10 PF
R55
100k
1
47
R52
47
R43
GNDA
TP17
DC_BIAS
0.6V
CT_I2-
1.2V -0.6V
C33
1000pF
CT_I2+
1.2V +0.6V
TP11
TP15
MC33502DG
-
+
U7A
2
DC_BIAS
2
LPF CUTOFF frequency
f3dB = 1/(2PI*(R43+R52)*C33)
f3dB = 1.7MHz
MC33502DG
7
GNDA
MC33502DG
R37
100k
+
U5A
C43
5
6
2
3
10 PF
C31
1UF
C25
GNDA
R21
1.8K
GNDA
G2 = (1+2*R37/R47)
G2 = 17.7
R55 = R47
TP18
1.2V -0.6V
C35
1000pF
3
DC bias voltage 0.6 V
R39
1.2V +0.6V
TP16
C30
1000pF
LPF CUTOFF 3.4MHz
V_OUT
TP13
MC33502DG
1
VDDA
R35
47
R38
100k
G1 = (1+2*R38/R46)
G1 = 17.7
R54 = R46
1.8K
R48
R45 R40
DC_BIAS
39 39 0.6V
1.8K
R42
R41
10 PF
C32
1k
R36
R30
4.7K
GNDA
VLINE
CURRENT SENSING USING CURRENTTRANSFORMER
Voltage measurement
N_IN
R29
100k
4
2
2
8
4
VDDA
3
3
5
8
+
-
4
1
1
8
4
+
Freescale Semiconductor, Inc.
-
Figure A-6. Low-cost analog schematic of the metering board with full CT configuration
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
71
100PF
C37
GNDA
0.1UF
C38
VDDA
Bypass capacitors
GNDA
0.1UF
C36
VDDA
BAV99LT1
2
BAV99LT1
D14
1
2
D13
1
BAV99LT1
2
D10
1
Input protection
VDDA
GNDA
VDDA
GNDA
VDDA
GNDA
GNDA
1
3
3
3
1
100PF
C39
CT_IN-
CT_IN+
VLINE
Supply connection
GNDA
VDDA
VDDA
GNDA
0.1UF
C50
VDDA
100PF
C51
A
B
C
D
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
72
Freescale Semiconductor, Inc.
Appendix B
Layouts
B.1 Layouts for full configuration
Figure B-1. Top side of the PCB
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
73
Layouts for full configuration
Figure B-2. Bottom side of the PCB
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
74
Freescale Semiconductor, Inc.
Appendix B Layouts
B.2 Layouts for Low-Cost Configuration with CT
Figure B-3. Top Side of the PCB with CT Low-Cost Configuration
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
75
Layouts for Low-Cost Configuration with CT
Figure B-4. Bottom Side of the PCB with CT Low-Cost Configuration
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
76
Freescale Semiconductor, Inc.
Appendix B Layouts
B.3 Layouts for Low-Cost Configuration with Shunt Resistor
Figure B-5. Top side of the PCB with shunt resistor configuration
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
77
Figure B-6. Bottom side of the PCB with shunt resistor configuration
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
78
Freescale Semiconductor, Inc.
Appendix C
BOM
C.1 Bill of Materials for Full Configuration
Table C-1. BOM report for full configuration
Part Reference
Quantity
Description
Manufacturer
Part Number
BT1
1
Battery holder CR2032
3V ROHS
COMPLIANT
Renata Batteries
SMTU2032-LF
C1,C2,C5,C8,C10,C11,
C12,C14,C15,C16,C18
,C21,C22,C36,C38,C4
0,C45,C47,C50
19
CAP CER 0.1UF 25V
10% X7R 0805
SMEC
MCCC104K2NRTF
C3,C7
2
CAP ALEL 47UF 6.3V
20% -- CASE C SMT
PANASONIC
EEE0JA470SR
C4,C6,C13,C17,C20,C
37,C39,C41,C51
9
CAP CER 100PF 50V
10% C0G 0805
AVX
08055A101KAT2A
C9,C28,C44,C46,C48
5
CAP CER 10UF 16V
10% X5R 0805
AVX
0805YD106KAT2A
C19
1
CAP TANT 2.2UF 16V
10% -- 3216-18
KEMET
T491A225K016AT
C23,C27,C31,C32,C42
,C43
6
CAP CER 10PF 50V
5% C0G 0805
KEMET
C0805C100J5GAC
C24,C29,C30,C33,C35
5
CAP CER 1000PF 50V
10% X7R 0805
AVX
08055C102KAT2A
C25,C49
2
CAP CER 1UF 25V
10% X5R 0805
Panasonic
ECJ2FB1E105K
D1,D3
2
DIODE ZNR 5.1V 0.5W
SOD123
ON
SEMICONDUCTOR
MMSZ5231BT1G
D2
1
LED GRN SGL 2mA
TH
Kingbright
WP7104LGD
D4
1
LED YEL SGL 2mA TH
Kingbright
WP7104LYD
D5,D15
2
LED RED SGL 2mA
TH
Kingbright
WP7104LSRD
Table continues on the next page...
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
79
Bill of Materials for Full Configuration
Table C-1. BOM report for full configuration (continued)
Part Reference
Quantity
Description
Manufacturer
Part Number
D6,D7,D8
3
DIODE SW 100V
SOD-123
ON
SEMICONDUCTOR
MMSD4148T1G
D9
1
LED IR SGL 100MA
TH
VISHAY
INTERTECHNOLOGY
TSAL4400
D10,D11,D12,D13,D14
5
DIODE DUAL SW
215MA 70V SOT23
ON
SEMICONDUCTOR
BAV99LT1G
D16
1
DIODE SCH DUAL CC
200MA 30V SOT23
ON
SEMICONDUCTOR
BAT54CLT1G
ISO1,ISO2,ISO3
3
IC OPTOCOUPLER
100MA 70V SMD
VISHAY
INTERTECHNOLOGY
SFH6106-4
J1,J2,J6,J7,J9,J11
6
CON 1X2 TB TH 5MM
SP 394H --
LUMBERG INC
KRM 02
J3,J4
2
HDR 2X3 TH 100MIL
CTR 335H AU 95L
SAMTEC
TSW-103-07-S-D
J5
1
CON 2X5 PLUG SHRD
TH 100MIL CTR 358H
AU 118L
ADAM
TECHNOLOGIES
BHR-10-VUA
J8
1
CON 2X20 SKT TH
100MIL CTR 335H SN
SAMTEC
SSW-120-01-T-D
J10,J13
2
JUMPER 3 PAD 40MIL
SQUARE SMT - NO
PART TO ORDER
N/A
N/A
LCD1
1
LCD DISPLAY 3V
64HZ TH
S-TEK INC
GD-3980P
L1,L2
2
IND CHIP
1UH@10MHZ 220MA
25%
TDK
MLZ2012A1R0PT
Q1
1
TRAN NPN AMP 0.5A
300V SOT-23
FAIRCHILD
MMBTA42
Q3
1
TRAN PHOTO NPN
250mA 30V TH
OPTEK
TECHNOLOGY INC
OP506B
TAMPER1,SW1,RESE
T1,SW2
4
SW SPDT PB 0.1A
30V TH
ZIPPY TECHNOLOGY
CORP
P12S1LZ
RS1
1
RES VARISTOR
275VRMS 10% 4.5kA
151J TH
epcos
B72220S0271K101
R1,R7
2
RES MF 4.70K 1/8W
1% 0805
BOURNS
CR0805-FX-4701ELF
R2,R5,R6,R14,R59
5
RES MF 330 OHM
1/8W 5% 0805
VISHAY
INTERTECHNOLOGY
CRCW0805330RJNEA
R3,R4
2
RES MF 220 OHM
1/8W 5% 0805
YAGEO AMERICA
RC0805JR-07220RL
R8
1
RES MF 680 OHM
1/8W 1% 0805
YAGEO AMERICA
RC0805FR-07680RL
Table continues on the next page...
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
80
Freescale Semiconductor, Inc.
Appendix C BOM
Table C-1. BOM report for full configuration (continued)
Part Reference
Quantity
Description
Manufacturer
Part Number
R9,R12,R60,R61
4
RES MF 1.00K 1/8W
1% 0805
KOA SPEER
RK73H2ATTD1001F
R10
1
RES MF 22K 1/8W 5%
0805
BOURNS
CR0805-JW-223ELF
R11,R15,R18,R39,R41
,R51,R53,R58
8
RES MF 10K 1/8W 5%
0805
VENKEL COMPANY
CR0805-8W-103JT
R13
1
RES MF 470.0 1/8W
5% 0805
BOURNS
CR0805-JW-471ELF
R20,R27,R35,R43,R44
,R49,R52
7
RES MF 47 OHM 1/8W
5% 0805
Rohm
MCR10EZPJ470
R21,R24,R25,R42,R48
5
RES MF 1.8K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-1K8BI
R22,R28,R34
3
RES MF 47K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-47KBI
R23,R29,R31,R33,R37
,R38,R54,R55
8
RES MF 100K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-100KBI
R26,R30
2
RES MF 4.7K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-4K7BI
R32,R57
2
RES MF 220K 1/4W
1% 50ppm MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204C-220KFI
R36
1
RES MF 1K 200V 0.1%
15PPM MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-1KBI
R40,R45
2
RES MF 39 OHM 200V
1% 50PPM MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204C-39RFI
R46,R47
2
RES MF 12K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-12KBI
R56
1
RES MF 390 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-390RBI
SJ1
1
JUMPER 2 PAD 40
MIL SQUARE SMT;NO
PART TO ORDER
N/A
N/A
TP1,TP2,TP3,TP4,TP5
,TP6,TP7,TP8,TP9,TP
10,TP11,TP12,TP13,T
P14,TP15,TP16,TP17,
TP18,TP19
19
TEST POINT TH PAD
60 DRILL 35 DIAM, NO
PART TO ORDER
NA
NO PART TO ORDER
Table continues on the next page...
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
81
Bill of Materials — Others Components
Table C-1. BOM report for full configuration (continued)
Part Reference
Quantity
Description
Manufacturer
Part Number
U1
1
IC MCU 32 BIT
ColdFire VI 256K
FLASH 16K RAM
2.5-3.6V/1.8-2.5V
LQFP100
FREESCALE
SEMICONDUCTOR
MCF51EM256CLL
U2
1
IC MEM MRAM 1Mb
SPI 2.7-3.6V DFN8
EVERSPIN
TECHNOLOGIES, INC
MR25H10CDC
U3,U4,U5,U7
4
IC LIN OPAMP DUAL
RAIL-TO-RAIL
1.0-7.0V SO8
ON
SEMICONDUCTOR
MC33502DG
U6
1
IC SENSOR
ACCELEROMETER
2.4-3.6V DFN10
FREESCALE
SEMICONDUCTOR
MMA7660FC
Y1
1
XTAL 32.768KHZ PAR
20PPM -- SMT
Citizen
CMR200T32.768KDZF
-UT
C.2 Bill of Materials — Others Components
Table C-2. BOM report —other components (non included in schematics)
QUANTITY
DESCRIPTION
MANUFACTURER
PART NUMBER
1
Current Transformer
Vacuumschmelze
T60404-E4626-X131
1
Shunt 150 microOhm
Zhongshan Weiqi Electronics
Co
WL150
1
Enclosure
FIBOX
PC 17/16-3
1
Open-frame AC/DC power
supply
XP Power
ECL05US03-T
1
Receptacle Cannon 9-pin
Tyco Electronics
1658609-4
2
Buttons termination - white
ZIPPY TECHNOLOGY
CORP
-
1
Buttons termination - black
ZIPPY TECHNOLOGY
CORP
-
1
Buttons termination - red
ZIPPY TECHNOLOGY
CORP
-
1
Receptacle 10-pin, ribbon
crimp
Tyco Electronics
1658622-1
1
3V battery
GP
CR2032
20 cm
Flat cable
any acceptable
-
2m
Extension Cord 250V/16A
any acceptable
-
1
Outlet 250V/16A
any acceptable
-
1
Power connector
SEZ
HSV 35
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
82
Freescale Semiconductor, Inc.
Appendix C BOM
C.3 Bill of Materials for Low-Cost (Basic) CT Configuration
Table C-3. BOM report for low-cost (basic) CT configuration
PART REFERENCE
QUANTITY
DESCRIPTION
MANUFACTURER
PART NUMBER
BT1
1
BATTERY HOLDER
CR2032 3V ROHS
COMPLIANT
RENATA BATTERIES
SMTU2032-LF
C1,C2,C5,C8,C10,C11,
C12,C14,C15,C16,C18
,C50
12
CAP CER 0.1UF 25V
10% X7R 0805
SMEC
MCCC104K2NRTF
C3,C7
2
CAP ALEL 47UF 6.3V
20% -- CASE C SMT
PANASONIC
EEE0JA470SR
C4,C6,C13,C17,C20,C
51
6
CAP CER 100PF 50V
10% C0G 0805
AVX
08055A101KAT2A
C9,C48
2
CAP CER 10UF 16V
10% X5R 0805
AVX
0805YD106KAT2A
C19
1
CAP TANT 2.2UF 16V
10% -- 3216-18
KEMET
T491A225K016AT
C30,C35
2
CAP CER 1000PF 50V
10% X7R 0805
AVX
08055C102KAT2A
C25,C49
2
CAP CER 1UF 25V
10% X5R 0805
Panasonic
ECJ2FB1E105K
D1,D3
2
DIODE ZNR 5.1V 0.5W
SOD123
ON
SEMICONDUCTOR
MMSZ5231BT1G
D2
1
LED GRN SGL 2mA
TH
Kingbright
WP7104LGD
D5,D15
2
LED RED SGL 2mA
TH
Kingbright
WP7104LSRD
D6,D7,D8
3
DIODE SW 100V
SOD-123
ON
SEMICONDUCTOR
MMSD4148T1G
D10,D13,D14
3
DIODE DUAL SW
215MA 70V SOT23
ON
SEMICONDUCTOR
BAV99LT1G
ISO1,ISO2
2
IC OPTOCOUPLER
100MA 70V SMD
VISHAY
INTERTECHNOLOGY
SFH6106-4
J1,J9,J11
3
CON 1X2 TB TH 5MM
SP 394H --
LUMBERG INC
KRM 02
J3
1
HDR 2X3 TH 100MIL
CTR 335H AU 95L
SAMTEC
TSW-103-07-S-D
J5
1
CON 2X5 PLUG SHRD
TH 100MIL CTR 358H
AU 118L
ADAM
TECHNOLOGIES
BHR-10-VUA
J10,J13
2
JUMPER 3 PAD 40MIL
SQUARE SMT - NO
PART TO ORDER
N/A
N/A
Table continues on the next page...
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
83
Bill of Materials for Low-Cost (Basic) CT Configuration
Table C-3. BOM report for low-cost (basic) CT configuration (continued)
PART REFERENCE
QUANTITY
DESCRIPTION
MANUFACTURER
PART NUMBER
LCD1
1
LCD DISPLAY 3V
64HZ TH
S-TEK INC
GD-3980P
L1,L2
2
IND CHIP
1UH@10MHZ 220MA
25%
TDK
MLZ2012A1R0PT
TAMPER1,SW1,RESE
T1,SW2
4
SW SPDT PB 0.1A
30V TH
ZIPPY TECHNOLOGY
CORP
P12S1LZ
RS1
1
RES VARISTOR
275VRMS 10% 4.5kA
151J TH
EPCOS
B72220S0271K101
R1,R7
2
RES MF 4.70K 1/8W
1% 0805
BOURNS
CR0805-FX-4701ELF
R2,R5,R6,R59
4
RES MF 330 OHM
1/8W 5% 0805
VISHAY
INTERTECHNOLOGY
CRCW0805330RJNEA
R9
1
RES MF 1.00K 1/8W
1% 0805
KOA SPEER
RK73H2ATTD1001F
R11,R15,R18,R58
4
RES MF 10K 1/8W 5%
0805
VENKEL COMPANY
CR0805-8W-103JT
R13
1
RES MF 470.0 1/8W
5% 0805
BOURNS
CR0805-JW-471ELF
R35,R44,R49
3
RES MF 47 OHM 1/8W
5% 0805
Rohm
MCR10EZPJ470
R21,R42,R48
3
RES MF 1.8K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-1K8BI
R34
1
RES MF 47K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-47KBI
R29,R33
2
RES MF 100K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-100KBI
R30
1
RES MF 4.7K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-4K7BI
R32,R57
2
RES MF 220K 1/4W
1% 50ppm MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204C-220KFI
R36
1
RES MF 1K 200V 0.1%
15PPM MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-1KBI
R40,R45
2
RES MF 39 OHM 200V
1% 50PPM MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204C-39RFI
Table continues on the next page...
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
84
Freescale Semiconductor, Inc.
Appendix C BOM
Table C-3. BOM report for low-cost (basic) CT configuration (continued)
PART REFERENCE
QUANTITY
DESCRIPTION
MANUFACTURER
PART NUMBER
R56
1
RES MF 390 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-390RBI
U1
1
IC MCU 32 BIT
ColdFire VI 256K
FLASH 16K RAM
2.5-3.6V/1.8-2.5V
LQFP100
FREESCALE
SEMICONDUCTOR
MCF51EM256CLL
U7
1
IC LIN OPAMP DUAL
RAIL-TO-RAIL
1.0-7.0V SO8
ON
SEMICONDUCTOR
MC33502DG
Y1
1
XTAL 32.768KHZ PAR
20PPM -- SMT
Citizen
CMR200T32.768KDZF
-UT
C.4 Bill of Materials for Low-Cost Shunt Resistor
Configuration
Table C-4. BOM report for shunt resistor configuration
PART REFERENCE
QUANTITY
DESCRIPTION
MANUFACTURER
PART NUMBER
BT1
1
BATTERY HOLDER
CR2032 3V ROHS
COMPLIANT
RENATA BATTERIES
SMTU2032-LF
C1,C2,C5,C8,C10,C11,
C12,C14,C15,C16,C18
,C21,C22,C40,C45,C4
7,C50
17
CAP CER 0.1UF 25V
10% X7R 0805
SMEC
MCCC104K2NRTF
C3,C7
2
CAP ALEL 47UF 6.3V
20% -- CASE C SMT
PANASONIC
EEE0JA470SR
C4,C6,C13,C17,C20,C
41,C51
7
CAP CER 100PF 50V
10% C0G 0805
AVX
08055A101KAT2A
C9,C28,C44,C46,C48
5
CAP CER 10UF 16V
10% X5R 0805
AVX
0805YD106KAT2A
C19
1
CAP TANT 2.2UF 16V
10% -- 3216-18
KEMET
T491A225K016AT
C23,C27
2
CAP CER 10PF 50V
5% C0G 0805
KEMET
C0805C100J5GAC
C24,C29,C30
3
CAP CER 1000PF 50V
10% X7R 0805
AVX
08055C102KAT2A
C25,C49
2
CAP CER 1UF 25V
10% X5R 0805
Panasonic
ECJ2FB1E105K
D1,D3
2
DIODE ZNR 5.1V 0.5W
SOD123
ON
SEMICONDUCTOR
MMSZ5231BT1G
Table continues on the next page...
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
85
Bill of Materials for Low-Cost Shunt Resistor Configuration
Table C-4. BOM report for shunt resistor configuration (continued)
PART REFERENCE
QUANTITY
DESCRIPTION
MANUFACTURER
PART NUMBER
D2
1
LED GRN SGL 2mA
TH
Kingbright
WP7104LGD
D5,D15
2
LED RED SGL 2mA
TH
Kingbright
WP7104LSRD
D6,D7,D8
3
DIODE SW 100V
SOD-123
ON
SEMICONDUCTOR
MMSD4148T1G
D10,D11,D12
3
DIODE DUAL SW
215MA 70V SOT23
ON
SEMICONDUCTOR
BAV99LT1G
ISO1,ISO2
2
IC OPTOCOUPLER
100MA 70V SMD
VISHAY
INTERTECHNOLOGY
SFH6106-4
J1,J6,J9
3
CON 1X2 TB TH 5MM
SP 394H --
LUMBERG INC
KRM 02
J3
1
HDR 2X3 TH 100MIL
CTR 335H AU 95L
SAMTEC
TSW-103-07-S-D
J5
1
CON 2X5 PLUG SHRD
TH 100MIL CTR 358H
AU 118L
ADAM
TECHNOLOGIES
BHR-10-VUA
J10,J13
2
JUMPER 3 PAD 40MIL
SQUARE SMT - NO
PART TO ORDER
N/A
N/A
LCD1
1
LCD DISPLAY 3V
64HZ TH
S-TEK INC
GD-3980P
L1,L2
2
IND CHIP
1UH@10MHZ 220MA
25%
TDK
MLZ2012A1R0PT
Q1
1
TRAN NPN AMP 0.5A
300V SOT-23
FAIRCHILD
MMBTA42
Q3
1
TRAN PHOTO NPN
250mA 30V TH
OPTEK
TECHNOLOGY INC
OP506B
TAMPER1,SW1,RESE
T1,SW2
4
SW SPDT PB 0.1A
30V TH
ZIPPY TECHNOLOGY
CORP
P12S1LZ
RS1
1
RES VARISTOR
275VRMS 10% 4.5kA
151J TH
EPCOS
B72220S0271K101
R1,R7
2
RES MF 4.70K 1/8W
1% 0805
BOURNS
CR0805-FX-4701ELF
R2,R5,R6,R59
4
RES MF 330 OHM
1/8W 5% 0805
VISHAY
INTERTECHNOLOGY
CRCW0805330RJNEA
R8
1
RES MF 680 OHM
1/8W 1% 0805
YAGEO AMERICA
RC0805FR-07680RL
R9,R12
2
RES MF 1.00K 1/8W
1% 0805
KOA SPEER
RK73H2ATTD1001F
R10
1
RES MF 22K 1/8W 5%
0805
BOURNS
CR0805-JW-223ELF
Table continues on the next page...
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
86
Freescale Semiconductor, Inc.
Table C-4. BOM report for shunt resistor configuration (continued)
PART REFERENCE
QUANTITY
DESCRIPTION
MANUFACTURER
PART NUMBER
R11,R15,R18,R58
4
RES MF 10K 1/8W 5%
0805
VENKEL COMPANY
CR0805-8W-103JT
R13
1
RES MF 470.0 1/8W
5% 0805
BOURNS
CR0805-JW-471ELF
R20,R27,R35
3
RES MF 47 OHM 1/8W
5% 0805
Rohm
MCR10EZPJ470
R21,R24,R25
3
RES MF 1.8K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-1K8BI
R22,R28,R34
3
RES MF 47K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-47KBI
R23,R29,R31,R33
4
RES MF 100K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-100KBI
R26,R30
2
RES MF 4.7K 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-4K7BI
R32,R57
2
RES MF 220K 1/4W
1% 50ppm MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204C-220KFI
R36
1
RES MF 1K 200V 0.1%
15PPM MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-1KBI
R56
1
RES MF 390 200V
0.1% 15PPM
MELF0204
WELWYN
COMPONENTS
LIMITED
WRM0204Y-390RBI
U1
1
IC MCU 32 BIT
ColdFire VI 256K
FLASH 16K RAM
2.5-3.6V/1.8-2.5V
LQFP100
FREESCALE
SEMICONDUCTOR
MCF51EM256CLL
U3,U7
2
IC LIN OPAMP DUAL
RAIL-TO-RAIL
1.0-7.0V SO8
ON
SEMICONDUCTOR
MC33502DG
Y1
1
XTAL 32.768KHZ PAR
20PPM -- SMT
Citizen
CMR200T32.768KDZF
-UT
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
Freescale Semiconductor, Inc.
87
MQX-Enabled MCF51EM256 Single-Phase Electricity Meter Reference Design, Rev. 0
88
Freescale Semiconductor, Inc.
Appendix D
References
D.1 References
1. http://cache.freescale.com/files/32bit/doc/ref_manual/MCF51EM256RM.pdf?
fpsp=1&WT_TYPE=Reference
Manuals&WT_VENDOR=FREESCALE&WT_FILE_FORMAT=pdf&WT_ASSET
=Documentation
2. http://cache.freescale.com/files/sensors/doc/data_sheet/MMA7660FC.pdf?fpsp=1
3. http://cache.freescale.com/files/rf_if/doc/ref_manual/1322xLPNRM.pdf?
fsrch=1&sr=1
4. http://cache.freescale.com/files/rf_if/doc/ref_manual/1322xSNRM.pdf?
fsrch=1&sr=1
5. http://en.wikipedia.org/wiki/Electricity_meter.
6. http://en.wikipedia.org/wiki/File:WorldMap_Voltage%26Frequency.png
7. http://en.wikipedia.org/wiki/Power_factor
8. http://en.wikipedia.org/wiki/AC_power
9. http://en.wikipedia.org/wiki/Current_transformer
10. http://en.wikipedia.org/wiki/Rogowski_coil
11. http://www.powerstudies.com/articles/PowerFactorBasics.pdf
12. http://cache.freescale.com/files/microcontrollers/doc/app_note/AN2295.pdf?
fsrch=1&sr=1
13. http://cache.freescale.com/files/rf_if/doc/user_guide/ZEDESDUG.pdf?fsrch=1&sr=1
14. AN4255: FFT-based Algorithm for Metering Application
15. Utility Meters/How To/Hacking in Energy Meters, Stephen Pickering
16. Utility Meters/How To/What Does an Electricity Meter Measure, Stephen Pickering
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Appendix E
E.1 Glossary
Analog to Digital Converter — ADC
Analog Front-End — AFE
Automatic Meter Reading — AMR
Bill of Materials — BOM
Common-Mode Rejection Ratio — CMRR
Current Transformer — CT
Fast Fourier Transform — FFT
General Purpose Input Output — GPIO
Graphical User Interface — GUI
Human Machine Interface — HMI
Integrated Circuit — IC
Inter-Integrated Circuit — IIC
Keyboard Interrupt — KBI
Light Emitting Diode — LED
Liquid Crystal Display — LCD
Microcontroller Unit — MCU
Open-Collector — OC
Printed Circuit Board — PCB
Programmable Delay Block — PDB
Programmable Analog Comparator — PRACMP
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Root Mean Square — RMS
Real Time Clock — RTC
Serial Communication Interface — SCI
Surface Mounted Device — SMD
Switch Mode Power Supply — SMPS
Serial Peripheral Interface — SPI
Zero-Cross Detection — ZCD
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