DESIGN (E) 314
TECHNICAL REPORT
Renewable Energy
Power Flow Management System
Author:
Kanda T
May 15, 2017
Student Number:
19362846
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19362846
Handtekening / Signature
T Kanda
Studentenommer / Student number
15/05/2017
Voorletters en van / Initials and surname
Datum / Date
1
Summary
The report discusses a renewable energy power flow management system. This
system has the solar panel as the source of renewable energy. The solar panel can is
either connected to the load resistor or a motor.
The details of the hardware design and implementation is discussed for each
hardware element. Descriptions of the main components are described with the help
of circuit diagrams. These components include LCD, RL78/G13 microprocessor and
temperature sense to mention a few. Software design and implementation is also
discussed. All of the user-level software functions involved in implementing the
operations are listed with brief descriptions. The main project file layout, as well as
the flow of control of the main program, is presented
The LCD is used to give a good interface between the user and the system and The
RL78 microcontroller provides a good integration work space for all data and
decisions made by the system.
2
Table of Contents
1 Introduction
5
2 System description
5
2.1 Main PCB System......................................................................................................................................................... 6
2.1.1 RL78/ G13 Microcontroller........................................................................................................................... 7
2.1.2 Power Supply ...................................................................................................................................................... 8
2.1.3 UART communications ................................................................................................................................. 8
2.1.4 Liquid Crystal Display....................................................................................................................................... 9
2.1.5 Temperature Sensor ..................................................................................................................................... 10
2.1.6 Switches ............................................................................................................................................................. 10
2.1.7 TLC081CP Operational Amplifier ............................................................................................................ 11
2.1.8 Push-buttons .................................................................................................................................................... 12
2.1.9 Electrically Erasable Programmable Read-Only Memory (EEPROM)...................................... 12
2.1.10
Operating modes ................................................................................................................................... 13
3 Chapter 3: Hardware design and implantation……………………………………………………………………………12
3.1
Power Supply………………………………………………………………………………………………………………..12
3.2
UART Communication……………………………………………………………………………………………………12
3.3
LCD……………………………………………………………………………………………………………………………….13
3.4
Temperature Sensor……………………………………………………………………………………………………...13
3.5
Current and Voltage Sensing…………………………………………………………………………………………..14
3.6
Switches………………………………………………………………………………………………………………………..15
3.7
Push Buttons…………………………………………………………………………………………………………………15
3.8
EEPROM………………………………………………………………………………………………………………………..16
4 Software Design ……………………………………………………………………………………………………………………….16
4.1
Main.C Functions……………………………………………………………………………………………………………16
4.2 User.c Functons………………………………………………………………………………………………………………17
4.3 Lcd.c Functions ……………………………………………………………………………………………………………...19
4.4 Project File layout…………………………………………………………………………………………………………...19
4.5 Flow Diagram of Main program control…………………………………………………………………………….21
4.6 Pheripheral setup and calibaration…………………………………………………………………………………...21
4.6.1 ADC………………………………………………………………………………………………………………………..21
4.6.2 Serial ….………………………………………………………………………………………………………………….22
4.6.3 Timers……………………………………………………………………………………………………………………22
4.6.4 Real-time Clock ……………………………………………………………………………………………………...23
4.6.5 Ports………………………………………………………………………………………………………………………23
5 Chapter 5: Measurements and Results
24
5.1
Power Supply………………………………………………………………………………………………………………….23
5.2
Push buttons…………………………………………………………………………………………………………………..24
5.3
Current and Voltage sensing……………………………………………………………………………………………24
5.4
Software program………………………………………………………………………………………………………….24
6 Conclusion………………………………………………………………………………………………………………………………25
References……………………………………………………………………………………………………………………………..25
Appendices
27
3
List of Abbreviations
A/D
Analogue to digital
ADC
Analogue to Digital Converter
ASCII
American Standard Code for Information
Interchange
BCD
Binary Coded Decimal
DC
Direct Current
I/O
Input and Output
LCD
Liquid Crystal Display
PC
Personal Computer
PCB
Printed Circuit Board
RAM
Random Access Memory
RTC
Real Time Clock
UART Universal Asynchronous Receiver/Transmitter
USB
Universal Serial Bus
TxD
Transmit Data
4
RxD
Receive Data
1 Introduction
An electronic renewable energy system monitor that can log power generated from both a
miniature solar panel .This system manages to control the power flow among the load resistor
and the motor. The RL78/G13 microprocessor was used to implement the system. The system
uses the commands which are received through the USB cable from a control on a PC or from
the buttons on the PCB.
For the system there are two modes of operation. These modes are Normal mode and Test
mode. The system runs automatically in the normal mode whilst in the test mode it waits for
the PC to execute tasks .In the normal mode the load resistor is connected to the solar and
when the temperature of the load resistor is high the solar automatically connects to the
motor load to dump energy. In the normal mode, push buttons are used to switch between
different loads.
The hardware and software details are provided in the report. In addition to that,
measurements from the system are given. Lastly a conclusion discussing how successful the
project was is given.
2 System description
This section of the report gives a detailed description on how the renewable energy monitor
system is made of. The block diagram below and circuit diagrams is used to describe the
operation of the whole system. It also explains how the system functions is related to the
different hardware components used. For the renewable energy monitor system, the
hardware components discussed are: the FT230XS UART, RL78/G13 microcontroller, LM7805
voltage regulator, Temperature sensor, PC1601-LCD, Push Buttons and the EPROM. The two
operating modes of the system namely Test Mode and Normal mode are is also discussed in
this section. Figure 1 shows the System Block Diagram.
5
Figure1: System Block Diagram
The system blocks are shown in Error! Reference source not found., with the major
components listed in Table 1.
Table 1: Main components Voltage range
Component
RL78/G13 Stick
FX230XS UART
LCD Module
EEPROM
Temperature
Sensor
Voltage Regulator
Push Buttons
2.1
Operating Voltage
2.0 V-5.5 V
3.3 V
5V
4.5V-5.5V
3V-5.5V
4.8V-5.2V
3V-5.5V
Main PCB System
The PCB has subsystems that work and coordinate with each other. The RL78/G14 acts as the
main component of the system consisting of input and output devices. Figure 2 show the PCB
System with hardware components
6
Figure 2: Main PCB System with hardware components
2.1.1 RL78/ G13 Microcontroller
The RL78/G13 processor from Renesas was used as the microcontroller of the system .As
the main brain of the system the RL78/G13 processor has the inputs and outputs components
connected to it.Renesas is currently the volume leader and the RL78/G13 processor is chosen
for this type of application because it is a fast complex instruction-set 16 bit with modern lowpower feature and good support. This processor also incorporates a R5F100LE processor (64pin with 64kB ROM Flash (program), 4kB Data Flash, 4kB RAM) and a hardware debugger
tool. It is very conveniently available in a low-cost promotion board with most of the I/O pins
exposed in two 30-pin header pins, thus also meeting the idea of a lower-pin count with
optimal amount of memory production hence suitable for the project. When mounted on the
PCB, the microcontroller chip uses 5V provided by the power supply. The controller uses an
external micro USB connected to the PC to program the device and for the debug purposes.
The
7
Figure 3: RL78/G13 Microcontroller Rails and Peripherals
2.1.2 Power Supply
The RL78/G13 microcontroller require a constant 5V supply. Thea LM7805 linear voltage
regulator is used to provide the constant voltage and to tolerate large peaks. The regulator
and all the regulated circuitry are protected from the reverse power connection by an extra
1N4007 protection diode which is in the power supply channel system. A 100Nf capacitor was
connected at the output for improved stability and transient response and also a 10Nf
capacitor was connected at the input to decrease the impedance from the source The power
supply will also provide a stable regulated +5V to the LCD display. The LM7805 regulator will
output a typical of +5V from an Input voltage of +7V to +20V and the output minimum and
maximum voltage being +4.8V and +5.2V respectively. Despite ensuring operation for the
system the voltage regulator acts as a safety mechanism since excess voltages can blow up the
components .It outputs a current of 5Ma which is very safe for other components in the
system.
Figure 4: Power supply and the Voltage regulator LM7805 to the system.
2.1.3
UART communications
8
Communication between the electronic renewable energy system monitor and the PC is
needed. The UART interface is added so debugging can still be done while communications to
PC uses separate UART port. The selected device for UART interface is the FTDI FT230XS IC. It
provides full UART functionality access from a PC USB port. Since the USB is not always at the
ground, large resistor values (1Mega ohm) are used to remove static voltage and small
capacitors (47pF) are used to filter out noise signals in transmission and reception processes.
100Nf capacitors are also used to stabilize the voltage for continuously changing signals The
UART communication is based on asynchronous bi-directional communication at moderate
speeds of 110 – 115200 baud. Since we operate over very short distances to the USB
translator, The UART port is set to 34800 baud in this design. The FTDI FT230XS has an
integrated level of +3.3V, however its logic inputs are 5V compatible hence the RxD input will
not be affected at 5V. Since VOH maximum for the FTDI FT230XS does not comply with the
R5F100LE VIH minimum in normal mode the TTL option for the RxD channel was chosen for
this project.
Figure 5: shows the USB to UART translator. Modified version of diagram in Practical 2
2.1.4 Liquid Crystal Display
The LCD screen acts as a device for displaying input signals as characters on a screen and
this provides a reliable interface between the user and the system. The LCD is used for
displaying switch states, real time date and any other messages which should be displayed. A
low cost 8 character x 2 line type display PC1601A LCD module with a choice of a 4-bit nibble
or 8-bit byte-orientated parallel interface is used. The LCD module is connected to the
microcontroller using 4 data lines DB4-DB7 whereas lines DB0-DB3 are grounded. It contains
three control bits Register Enable (E), Read-Not-Write (R/W) and Select (RS. In the setup, the
LCD is initially initialized to the 4-bit mode operation. Writing on the LCD occurs when both
RS and R/W equal 0. Reading from microcontroller occurs when R/W and RS equal 1.For both
commands Enable must be equal to 1. For the LCD contrast a potential divider was used.
Beside its low cost the LCD’s operating voltage ranges from 2.7 to 5 V and this makes it
suitable for the project system.
9
Figure 6: LCD Circuit diagram. Modified version of diagram in Practical 2
2.1.5 Temperature Sensor
The LMT01-Q1 is a high-accuracy 2 pin temperature sensor provides a digital output in the form
of a pulse count that is transmitted by a train of current pulses. When it is powered up it will
transmit a very low current for less than 54ms while the part executes a temperature to digital
conversion. The temperature sensor is attached to the load resistor so as to measure the
temperature of the load resistor. This is done so as to ensure that the temperature of the load
resistor stay in the required region. The temperature sensor then transmit a series of pulses
equivalent to the pulse count at a given temperature. The total time for temperature to digital
conversion and the pulse train time interval is 104ms.The pulse train keeps on repeating itself if
power is applied periodically .The temperate sensor will output at minimum 1 pulse and a
theoretical maximum of 4905 pulses. Each pulse has a weight of 0.0625⁰C with 1 pulse
corresponding to a temperature less than -50⁰C. Figure 4 shows how the pulse diagram and how
the temperature sensor is connected to the microcontroller.
.
Figure 7: Pulse diagram and LMT01-Q1 2-pin Temp sensor.
2.1.6 Switches
The only required source of power in this project was the solar panel as per the project
specification requirements. This source of power either drives the load resister as a primary
load or switches on the drive to the motor just as the load the load resistor becomes too hot.
For this power flow management to be fluent 3 digital switches were implemented by using 3
10
2N700 MOSFETs and a 2 HRS1KH-S Relays.This MOSFET, which has a rated current of 200mA
was used because it has fast switching times, improved inductive ruggedness, lower input
capacitance, extended safe operating area and improved high temperature reliability. The
relay driver was also used since it can handle the 5V supplied to the boards for electromagnetic switching. Electrical isolation is also provided by the fly-back diode which is in the
relay circuit. MOFSET switches were used to supply a driving current to the relay thereby
enabling the microcontroller to connect the solar panel to the motor or load resistor. The
MOSFET was not used as a direct short circuit switch as they are easily blown off if too much
current flows through.
Figure 8a: MOSFET 2N700
Figure 8b: HRS1KH Relay driver circuit
2.1.7 TLC081CP Operational Amplifier
Current sensing circuits to measure the solar panel short circuit current, and current supplied
from the solar panel to the loads were build using the TLC081CP Operational Amplifier. The
low side current sensing was used to measure current flowing to the ground through small
sense resistor (RSENSE). The low-side current sense circuit in figure 6 is used because voltage
drop is easy to measure since it is with respect to ground. To implement this, voltage (VSENSE )
drop across the current sense resistor is measured and then Ohms law(VSENSE = ISENSE RSENSE)
is used to calculate ISENSE. VSENSE is then amplified to an analogue VADC value by making use of
Rf
the gain of the amplifier according to the amplifier equation Vadc = Vsense ∗ (1 + R2),
whereby RF is the feedback resistor and R2 . The voltage is amplified so as to provide a signal
with suitable range for the RL78 analog-to-digital converter ADC. The supply voltage and
current required by the op amp is 4.5V and 57mA therefore making it is suitable for the
project.
11
TLC0
81CP
R
L78/
G13
Figure 9: TLC081CP Operational Amplifier. Modified version in Lecture 6.
2.1.8 Push-buttons
The push buttons were added to the system for user interaction with the
microcontroller. The buttons inputs to the microcontroller have the pull resistors
and when pressed they connect to the ground. The user control comprises of 4
buttons with different functionalities depending in the type of mode you will be in
Test mode or Normal mode.When the system is running in Test mode the buttons
are used to switch the states and when in the Normal mode the buttons are used to
adjust date, time and to test the solar panel. The figure below shows the buttons
added to the system.
Figure 10: Push Buttons
2.1.9 Electrically Erasable Programmable Read-Only Memory (EEPROM)
The system monitor must be able to log information about the power generated prior to
the project specification. To implement this an external storage for log data, a 64kbit (8192 x
8bit) 25LC640 8-pin DIP microchip, was connected to the RL78. . The microchip has a 3-wire
interface with SI, SO and SCK being the interfaces signals. SCK is used as a clock input at 1MHz,
SI is used as separate data in line and SO is used as separate data out line. The operating
voltage of the microchip is 4.5-5.5V and also it uses low-power CMOS technology thus making
12
it suitable for the project .It has a write current of 3mA and a read current of 500µA both
which are within the board limits hence making it suitable for the project. The RL78 only
controlled the not CS pin to enable/disable the microchip. The voltage and temperature
measurement, current switch state, current date/time, load current measurement and
calibrated temperature values are logged onto the EEPROM every second. This is possible
since the microchip has 5ms max write cycle time. This logged information can be taken from
the EEPROM via the UART to the PC.
Figure 11: 25LC640 8-pin DIP microchip
2.1.10 Operating modes
Two operating modes namely normal mode and test mode were used for the system.
The system runs a certain task automatically in normal mode and this is the start-up mode of
the system. In this mode the controller execute a programmable schedule as well as a logic on
which state to execute. A certain range of temperature is calibrated so at to control the load
temperature. This temperature is sampled at certain intervals of time by the RL78.Either the
load resistor or the motor load is driven by the solar depending on the temperature. The
sequence goes this way, while the temperature reaches a specified maximum value the
controller independently switches the solar panel to drive the only the motor thereby
allowing the load resistor to cool. When the temperature reaches a minimum value the
microcontroller switches the solar panel to drive the load resistor. The voltage and
temperature measurement, current switch state, current date/time, load current
measurement and calibrated temperature values are logged onto the EEPROM ever second. In
this normal mode, push buttons are also used to perform solar panel test and the setting of
the real time clock.
For the second mode, Test mode, the system waits for certain commands from the PC so as to
execute certain tasks such as reading and writing from the EEPROM. In this mode buttons are
used to go through different switch states. Each time the new state switch is displayed on the
LCD.
3 Chapter 3: Hardware design and implantation
In the design of the system, many design choices had to be made. This was done so that all
hardware components meet their perspective tasks. This chapter explains the choices of the
components used in the entire system together with their calculated values. It also gives a
13
detailed description of the of the system design with motivation on the design choices and
assumptions made.
3.1 Power supply
A suitable power supply was designed to provide an output of +5V for the microcontroller
and display (LCD). From the datasheets: LM7805 Input voltage Vin (min) = 7 V
1N4007 Forward voltage Vd1 (max) ≈ 0.8 V
Since the LM7805 requires at least 7V and the forward voltage is 0.8V.The total voltage for
needed for the input is now 7.8V.It is know that standard batteries have 6V, 9V AND 12V
output voltage. So as not to drain the supply voltage I chose my input voltage to be
≥9.8V.Considering the worst case scenario I designed for an input voltage range of 12
≤Vinput≥ 10v at a current of 0.24A at max. From the datasheet of the LM7805 voltage
regulator C3 = 100nF, C2 = 10Nf.The output capacitance improve stability and the input
capacitance helps to reduce the source impedance.
Figure 12: Power supply circuit
3.2 UART communications
The UART TxD and RxD lines provides the channel of data transmission to and from the
microcontroller. They are connected to the ports P04 and p03 and current flow through this
ports. The maximum current that flows through the ports is 20mA as from the RL78 data
sheet. To avoid any excess dead parasitic current I designed for resistors which I connected
between the TxD and RxD ports of the FT230XS UART and the RL78 G13 microcontroller.
14
Figure 12: Representative circuit diagram of connection between FT230X and R5F104LE
Since the input voltage is 5V and the max current is 20mA. Applying Ohms law the
𝑉𝐷𝐷
5
minimum resistance is: Rmin = 𝐼𝑚𝑎𝑥 = 0.02 = 250Ω
R1 and R2 was chosen to be 1000Ω to make sure that a maximum current of 5mA, which is
extremely below 20mA, can flow through.
3.3 Liquid Crystal Display (LCD)
For the LCD contrast, a resistor is used in the LCD potential divider to limit the amount of
current. The resistors R1 and R2 in the schematic diagram below affect the contrast of the
LCD.R1 was set to 18kΩ.Since this 2 resistors form a potentiometer, I adjusted R2 until I
observed a satisfactory contrast on the LCD.A 800Ω
Figure 13: Section of LCD circuit
3.4 Temperature sensor
In the RL78 datasheet using the TTL Vin max is 0.8V and Vmin is 2.2V,and also from the
LMT01 datasheet the values for the typical temperature sensor I(Low) is 34µA and the
value for I(inmax 0)is 125 µA. From Ohms law (V = IR): The approximate minimum value
of the resistor to be used to convert pulses from the temperature sense can be calculated.
𝑉𝑖𝑙
Rminimum = 𝐼𝑖𝑙𝑜𝑤 = 0.8V/34µA = 17600Ω
15
Rmaximum =
𝑉𝑖ℎ𝑖𝑔ℎ
𝐼𝑖ℎ𝑖𝑔ℎ
= 2.2V/125µA = 23500Ω
I then chose a resistor value of 22k Ω which is in between the range 17 000 < R < 23 500
The resistor value also met the condition of Vn > 3V, since 125µA*22k Ω= 2.75v
3.5 Current and voltage sensing
Rsense, the current sense resistor, was designed to have a low resistance value as possible so
the current through this resistor be almost equal to the current which has to be measured.
A design constraint that the power rating of 0.25W of the resistors available should be not
exceeded.
Since Pmax= Imax2Rmax
0.25
Rmax = 0.25 = 1Ω
Since the 1Ω resistors had high variability of +0.5 Ω. Or -0.5 Ω when measured in the lab, I
did choose to connect 1.2 Ω resistors in parallel to yield an equivalent resistance of 0.6 Ω
This low resistor value ensured that a lower current flows through each resistor hence not
exceeding
its maximum wattage required.
Gain: For Motor Op Amp:
This maximum measured value for the motor current 560mA .
Vsense = 0.56 x 0.6
= 0.336V
For worst case scenario for Vadc = 5.2V and
𝑅𝑓
Vadc = Vsense x (1 + 𝑅2)
I calculated
𝑅𝑓
𝑅2
as shown below
𝑅𝑓
Vadc = Vsense x (1 + 𝑅2)
5 = 0.336 x (1 +
𝑅𝑓
𝑅2
𝑅𝑓
𝑅2
)
=14
I then chose Rf = 14kΩ and R2 = 1kΩ
My design held since for both the op amps saturation did not occur during measurements.
Gain: Load Resistor op amp:
This maximum measured value for load resistor current was found to be 0.45A. I used a
Rsense = 0.6Ω
Vsense = 0.45 x 0.6
16
= 0.27V
For worst case scenario Vadc = 5.2 V and
𝑅𝑓
Vadc = Vsense x (1 + 𝑅2)
𝑅𝑓
𝑅2
was calculated as shown below
𝑅𝑓
Vadc = Vsense x (1 + 𝑅2)
5
𝑅𝑓
𝑅2
𝑅𝑓
= 0.27(1 + 𝑅2 )
= 18.5
I then went on to choose Rf = 20kΩ and R2 = 1kΩ
3.6 Switches
Figure 13b: MOSFET switch
Vgate = 2.2V From the MOSFET data sheet.
Using nodal analysis at the gate node
(Vgate – Vinput)/ Rin + Vg/Rgs =0
(2.2-5) /Rin + 2.2/Rgs = 0
2.2/Rgs = 2.8/Rin
Rin = 1.272Rgs
Resistor values chosen
Rin = 13kΩ
Rgs = 1kΩ
Used in all the 3 circuits to ensure switching.
17
3.7 Push Buttons
As shown in the figure below, I designed for pull up resistors. When the button is pressed,
the input is made low thefore Vin<Vmax, and the button is not pressed, the input pin is made
high there Vin >Vmin. From the RL78 datasheet R3 is 100k Ω
Figure 14: Schematic circuit for Push buttons
3.8 EEPROM
A designed for a decoupling capacitor, small 10nF, between Vcc and ground
near the EEPROM to make sure that all the high frequency noise from the power
supply is filtered off and won’t affect the stored information in the EEPROM.
4 Software Design
4.1 Main.C Functions
void main (void)
This function implements the main function. The initializing function, R_MAIN_UserInit(), is
called in the main. This is followed by an infinite while loop which calls the functions
responsible for the reaction of the flags of the UART which in-turn stimulates the
communication of our system with the PC. It also calls functions which start the timers for a
number of channels and also functions which setup certain flags for other different commands.
The
functions
serviceUart(),SCROLLONGTEXT(lcd_bufter),initLcd(),
writeString(show),R_TAU0_Channel1_Stop() and R_TAU0_Channel1_Start() are also called in
the infinite while loop.
18
void main(void)
{
R_MAIN_UserInit ();
/* Start user code. Do not edit comment generated here */
R_TAU0_Create ();
R_TAU0_Channel2_Start ();
//Create and initialize the UART
States_C=0;
State_N = 11;
int tcout=0;
R_UART1_Create ();
R_UART1_Start ();
R_RTC_Creat e();
R_RTC_Start ();
R_IT_Create ();
R_IT_Start ();
uart1Status = R_UART1_Receive (&uart1RxBuf[0], 1);
initLcd();
}
while (1U)
{
In the main function this is where the Test mode or the Normal mode are executed. This
modes are executed when their flags are set to high. The software for activating the buttons is
also in the while loop of main function
void R_MAIN_UserInit(void)
This function calls the timer initializing function, real time clock, and the LCD initialize and
communication channels.
void UartSend(void)
The function writes out information from the UART0.The function wait for the lag to be set
high and this happens after all information is send from the UART then is can continue
4.2 User.c Functions
void serviceUart (void)
This function is continuously called in the while loop which is in the void main (void) function.
It stores the data in the command of the UART0 after receiving it. The function executes
through only if there are available bytes from the UART. A This bytes are then loaded to an
array.
void UartSend(void)
The function writes out information from the UART0 . The function wait for the flag to be set
high, thus after all the information is send from the UART then it can continue.
void INSTRUCT(void)
19
This function uses a switch statement to implement the state machine. The switch statement
switches the menu to the Test mode as well as the Normal mode depending on the commands
from the user.The different cases with different functions are case '0' : go to normal mode
case '1' : go to test mode
case '2' : load the LCD with certain characters
case '3' : load the student number
case 'D' : display message loaded into the LCD
case 'E': display measured values of voltage or
current
case 'I': show the temperature
case 'C': return the present time
case 'N': temperature turn on or off
default: invalid command or does not exist.
void Mode toNormal(void)
This functions sets the normal mode flag to 1 and puts the system in the normal mode by
transmitting (0x00) to the PC.
void Mode toTest(void)
This functions sets the test mode flag to 1 and puts the system in the test mode by
transmitting (0x10) to the PC.
void INVALID_PARAM(void)
This function transmit an invalid message back to the PC when an invalid character is
transmitted to the system
void WELCOME_TEXT(void)
This function sends a welcoming message to the PC when the system is powered up
void SOLAR_toSWITCH(void)
This function uses a switch statement to set the switch states. Depending on which state the
system is in, the solar connects either to the load resistor or to the motor. If the solar is not
connected to any of this it is short circuited. This is all implemented in the SOLAR toSWITCH
function by setting the flags of the motor and load resistor. The function short circuits the
solar panel by assigning the port 43 of the RL78 to 1.It also connects the solar panel to the
motor by assigning the RL78 port 42 to 1 whilst port 41 and port 43 are assigned to zero. The
solar panel is connected to the load resistor by assigning the port 41 to 1 whilst pots 42 and
43 are assigned to 0. All switches are opened by assigning all the 3 ports of the RL78 to 0.
void R_ADC_Get_Result(uint8_t * const storeAdc)
This function shift the conversion result, ADCR, to the right by 6 (*buffer = (uint16_t) (ADCR
>> 6U) and write this value address of the variable which is sent to it. It then gets the digital
output value after the ADC conversion.
void Measure(void)
This function first calls the functions R_ADC_Create () and R_ADC_Start () which initializes
and start the AD convetor. It then calls the function R_ADC_Get_Result_8bit(&measuredvalue)
which returns the higher 8 bits conversion result of the measured value and writes it in the
address of measured value. The function is called a multiple number of times and it returns
different values which are then averaged to get an accurate value.
20
void TEMP_GOT(void)
This function gets the value of the pulses of the temperature sensor and then converts this
pulse to a decimal value of the temperature in degree Celsius. In this function the 2 channels,
R_TAU0_Channel1_Start()and R_TAU0_Channel1_Start(), are started. This pulse counted are
store in variable KAY. This pulses are then used to calculate the temperature value in degree
𝑃𝐶
Celsius according to the formula in LMT01-Q1 data sheet, Temp = (4096 × 256) − 50℃ , where
PC is the pulse count and Temp is the temperature reading.
void TEMPOF_ON(void)
This function sends the measured valued of the temperature to the UART.
uint8_t DECIMALToBCD(uint8_t DECvalue)
This function is used to change the decimal value sent to it to a BCD value. It’s done by left
shifting the decimal value by 4 and then bitwise OR the result with the units value of the
decimal value: BCDValue = ((DECvalue/10)<<4) | (DECvalue%10)
uint8_t bcdToDecimal (uint8_t BCDvalue)
This function is used to change BCD value sent to it to an integer value. It’s done by right
shifting the upper nibble value of the BCD value by 4 and then adding the result with the
lower nibble value of the BCD value: DECvalue= (upperNibble >> 4) + lowerNibble.
void PrintMeasure(void)
This function calls the function Measure().It gets the measured values of voltage, solar current
and load current. It the sends this values to microcontroller and then stored in certain
registers.
void returnTimem (rtc_counter_value_t current time)
This function receives a struct containing bytes received from the PC .It then checks if the last
5 bytes shows a valid time and date. If the bytes are valid, the specified time is then converted
to BCD format and then get set to the RTC using the generated R_RTC_Set_CounterValue()
function.
void Auto_Switch(void)
This function checks if the temperature is low or high. If the temperature is high it
automatically switches on the motor by connecting the solar panel to the motor and if the
temperature is low it automatically connects the solar panel to load resistor.
4.3 Lcd.c Functions
void writeByteLcd(uint8_t reg,uint8_t value)
This function writes 2 nibbles to the LCD. reg (BOOL) 0 = register, 1 = data
value(BYTE) -first the upper 4 bits then 4 lower bits
void writeNibbleLcd(uint8_t reg,uint8_t nibble)
This function writes a nibble to the LCD. reg (BOOL) 0 = register, 1 = data
nibble(BYTE) -first the upper 4 bits then 4 lower bits
void initLcd(void)
21
This function initializes the LCD. It also calls a function CLEARLCD which clears the LCD
screen.
void delayNoInt(uint16 t delay)
void startTMR0(int delay)
These 2 functions are from the lecture slides. They are used to implement a delay in
microseconds. The first function uses this timer to cause delay in operations and the second
function starts the timer.
void DisplaySTRING(uint8_*TkAY)
This function displays an array of characters on the LCD. If the characters become greater
than 16 the function RIGHTSHIFT(Tkay) is called. This function shifts the characters on the
LCD to the right at a rate of 500ms and displays them. This implements scrolling.
4.4 Project File Layout
Globvalues.c
iodefine_ext.h
iodefine.h
r_cg_cgc.h
r_cg_intc_user.c
r_cg_intc.c
r_cg_intc.h
r_cg_interrupt_handlers.h
r_cg_macrodriver.h
r_cg_pclbuz_user.c
lcd.c
lcd.h
r_cg_adc_user.c
r_cg_adc.c
r_cg_adc.h
r_cg_cgc_user.c
r_cg_cgc.c
r_cg_port_user.c
r_cg_serial_user.c
r_cg_serial.c
r_cg_serial.h
r_cg_timer_user.c
r_cg_timer.c
user.c
user.h
r_cg_timer.h
r_cg_port.c
r_cg_port.h
r_cg_rtc_user.c
r_cg_rtc.c
r_cg_rtc.h
r_cg_userdefine.h
r_cg_vector_table.c
r_hardware_setup.c
22
r_main.c
r_reset_program.asm
4.5 Flow Diagram of Main program control
23
4.6 Peripheral setup and calibration
The RL78 set up peripherals for successful implementation of the project are as follows.
4.6.1 ADC
The reference voltage of the A/D convertor was set to Vcc = 5V while the minimum
reference was 0V.Its resolution was set to 8bits.The ADC will only get changed by the software
since the software trigger mode was selected.3 inputs which are analog were selected and all
of them being continuous select mode. For the conversions the following formula was used.
𝐷𝑖𝑔𝑖𝑡𝑎𝑙 𝑉𝑎𝑙 =
𝐴𝑛𝑎𝑙𝑜𝑔 𝑉𝑎𝑙
× 𝑉𝑐𝑐
28
4.6.2 Serial
Channel 0 and channel 2 were used.CS100 was selected for channel 1 whilist for channel 2
UART1 was selected. This channels were both set to Transmit and Receive. For the UART1 it
was set to receive data of 8bits long with no parity bit. The baudrate was set to 38400bps.
This was the specification of the design. For the CS100 the baudrate was to be 100kbps and
the internal clock was set to clock mode.
4.6.3 Timers
Two timers’ namely External timer and Interval timer were set up. The project protocol
specification required the system to be respond quickly. For channel 0, the interval timer was
set to run for 20ms.This means that an interrupt is generated after every 20ms.This interval
timer was used for the LCD scrolling. As per project specification the LCD was supposed to
scroll at a rate of 500ms per character.
External event counter was set to operate at 16 bits and max frequency of 500MHZ. The
external event counter was set to start at a count value of 4094. After a falling edge is detected
this count value decrements and is stored in the TCR01 register. A count value of 4094 was
chosen since the maximum number of pulses generated by the temperature sensor is
4095.The temperature sensor used the interval timer as well as the external counter.
4.6.4 Real-time Clock
An interrupt for the real time clock was set to generate every second .The real time clock was
set up to be used in the 24 hour system.
4.6.5 Ports
All the inputs and outputs pins used on the RL78 stick where selected on the ports peripherals
and then generated.
5 Chapter 5: Measurements and Results
In order to assess the accuracy of the completed systems, measurements were taken from the
system and this were listed below. The system is fully operational with the exception of the
EEPROM.
24
5.1 Power Supply
Input voltage(v) Output Voltage(v)
7
10
12
26
5.2
5.2
5.3
6.3
Table 2: Power supply
Figure 15: Power supply output
The measured values for the power supply shows that a constant supply of 5.2V to the
system is maintained. The voltage regulator only outputs a constant voltage of 5.2V
when an input voltage of 7V to 20V is supplied from a DC source
5.2 Push buttons
Figure 16: Lcd Voltage
Voltage for Push buttons = 5.4V when pressed and aprox 0V when not pressed.
5.3 Current and voltage sensing
Current from the load = 0.45 Amp
Current from the Motor = 0.56 Amp
5.4 Software program
The program software use the memory shown in figure 17
25
Figure 17: Memory used
6 Conclusions
The goal of the design was to create an electronic renewable energy monitor that can log
power generated from miniature solar panel. The final system was fully operational
(excluding the EEPROM).This was because of failing to implement the software for EEPROM.
The user can however be able to navigate through the menu using the push buttons. The
system can control the amount of power through the load resistor by sensing the temperature
of the load resistor at a time interval. The system will automatically connects to the motor
when the wattage of the load resistor is being exceeded (temperature becomes too high).
The communication through the USB responded correctly to the commands requested by the
user. The system also displays relevant information to the user as per speciation for the
project. However the gains of 20(for load) and 14(for motor) which were used to amplify the
voltage and current values of the solar panel, load and motor needs to be improved since, at
the end, the system failed to produce the ADC values in the required range as per protocol
specification.
References
[1]
J. M. Alexander G.Dean, Creating Fast, Responsive and Energy-Efficient Embedded
Systems using the Renesas RL78 Mirocontroller, Weston: Micrium Press, 2012.
[2]
Renesas, "RL78/G14 Datasheet - Renesas Electronics," 05 January 2015. [Online].
Available:
http://documentation.renesas.com/doc/products/mpumcu/doc/rl78/r01ds0053ej03
20_rl78g13.pdf. [Accessed 14 May 2017].
[3]
LMT01-Q1 0.5°C Accurate 2-Pin Digital Output Temperature Sensor with Pulse Count
Interface, LMT01-Q1 datasheet, Texas Instruments, Nov. 2017,
[4]
FT230X USB to Basic UART IC, FT230X Datasheet, Future Technology Devices
International Ltd, 2016.
[5]
HITACHI, "HITACHI, Ltd Semiconductor and Integrated Circuits," 1998. [Online].
Available: https://www.sparkfun.com/datasheets/LCD/HD44780.pdf. [Accessed 8 May
2017].
26
[6]
A. Barnard and L. Visagie , "Design (E) 314 Lectures," Stellenbosch, 2017.
[7]
"Diodes Incorporated 1N4001," [Online]. Available:
www.diodes.com/_files/datasheets/ds28002.pdf. [Accessed 11 May 2016].
[8]
R. MCU, "RL78/G13," 2013. [Online]. Available:
http://www.renesas.eu/products/mpumcu/rl78/rl78g1x/rl78g12/app_notes.jsp.
[Accessed 12 May 2017].
Appendices
Appendix A Complete Schematic
27
Appendix B Technical specification
Power Supply:
Main PCB: 9-12V,
0.18 -0.36mA
External Connections
Solar panel
USB cable
DC power supply
28
LCD display
Screen width: 16 characters
Strings longer than 16 characters scroll to the left at a rate of 500ms character/s
until complete
Appendix C Circuit Diagrams and Tables
RL78 Pins Used and their Configuration
Project function
RL78 R5F100LE - 64 pin device
RPB UART
Function
UART2 RX
UART2 TX
Port
P13
P14
Type
IN
OUT
Pin
43
42
FT230XS UART
UART1 RX
P03
IN, TTL
61
J2-8
UART1 TX
P02
OUT
62
J2-7
D0/4
P74
OUT, (IN)
25
J1-25
D1/5
P75
OUT, (IN)
24
J1-24
D2/6
D3/7
E
R/W
RS
P76
P77
P72
P71
P70
OUT, (IN)
OUT, (IN)
OUT
OUT
OUT
23
22
27
28
29
J1-23
J1-22
J1-27
J1-28
J1-29
Enable
P41
OUT
4
J2-23
Voltage
P20
IN/ANA
56
J2-11
Current
P21
IN/ANA
55
J2-12
Motor(2nd Load)
Enable
P42
OUT
3
J2-22
Short circuit
Voltage
Current
Enable
P22
P23
P43
IN/ANA
IN/ANA
OUT
54
53
2
J2-13
J2-14
J2-21
LCD
Solar
29
PCB Pin
J1, J2
J1-6
J1-7
Power supply
Microcontroller module
Lcd Interface
30
Temperature sensor
Current and Voltage sensing
Push Buttons
31
EEPROM
Voltage Regulator
32