Oneil Kwangwanh
ETEC471 – Project Description
12.11.2012
DDM – Digital Diameter Meter
0
TABLE OF CONTENTS
FUNCTIONAL DESCRIPTION……………………………………………………………………………………………………………………..2
Introduction………………………………………………………………………………………………………………………………..2
Description and Sketch...…………………………………………………………………………………………………………….2
Features…….……………………………………………………………………………………………………………………………….3
Detailed Functional Description…………………..……………………………………………………………………………..3
Software……………………………………………………………………………………………………………………………………..4
User Interface……………………………………………………………………………………………………………………………..4
STANDARDS…………………………………………………………………………………………………………………..………………………..6
DEVELOPMENT PLAN……………………………………………………………………………………………………………….……………..6
Weekly Schedule………………………………………………………………………………………………………………….……..6
Description of Hardware/Software…………………………………………………………………………..………….……..7
Description of Demonstration……………………………………………………………………………………….….………..7
ELECTRICAL SPECIFICATIONS……………………………………………………………………………………………………………………7
Project Specifications………………………………………………………………………………………………………..………..7
Power Requirements.………………………………………………………………………………………………………………….7
Special Environmental Requirements………………………………………………………………………………………….7
PRELIMINARY PARTS LIST…………………………………………………………………………………………………………………………8
1
FUNCTIONAL DESCRIPTION
a. Introduction:
The Digital Diameter Meter (DDM) is a device that will digitize the process of measuring
the diameter of pipes. The user will be able to quickly measure pipe diameters ranging from
6 inches all the way up to 96 inches in diameter.
b. Description & Sketch:
The purpose of the DDM is to digitize the process of measuring the diameter of pipes.
The idea was first realized by Todd Bishop, president and owner of BRER Technical, INC.,
when his employees found themselves atop tall ladders trying to wrap measuring tapes
around large pipes. Referring to Figure 1, the DDM will have a fixed “W” and will use a
rotary encoder to measure “H” of a given pipe. I will need to convert the value returned by
the encoder to an “H” value in inches. Using these two values, the microcontroller will then
calculate radius and diameter, and output calculated diameter and the closest standard size
to an LCD display.
FIGURE 1
FIGURE 2: Side view sketch of DDM
2
c. Features:
1. Accurately calculate the diameter of a given pipe ranging from 6” to 96” in
diameter.
d. Detailed Functional Description:
FIGURE 3: Block diagram
Microcontroller
The ideal and actual microcontroller used for the DDM is an ATMega328P. This 28-pin
chip features 32KB of flash memory, 1KB of EEPROM, and 2KB of internal SRAM. The
resources used will be the MCU’s SPI and GPIO. The SPI for the LCD display and the GPIO in
order to read data from the encoder. One external switch will have to be used in order to
run the interrupt service routine that will sample data from the encoder.
Rotary Encoder
The ideal encoder used for measurements would be one with a digital output such as
the E6B2-CWZ6C. This specific encoder has five wires: power supply, output phase A,
output phase B, output phase Z, and ground. Connecting the output phases to 3 GPIO pins
on the ATMega328P, the DDM will be able to monitor the amount of pulses the encoder has
revolved.
LCD Display
If we look at FIGURE 5, we see an example of an output to the LCD display. This
example is 29 pixels tall and 38 pixels wide and shows the largest message that needs to be
3
displayed. The smallest standard LCD display is 48x84 and ideally would communicate with
the ATMega328P over SPI.
Power Supply
Both the encoder and the MCU will need a 5V power supply, while the LCD Display has a
maximum power supply voltage of 3.3V. Because two different power supplies are required
for the system, one dual output buck converter will be used sourced from one 9V battery.
e. Software:
The program used to read and handle data from the encoder and to output to the LCD
display will all be written in the C programming language. I will be using Atmel studio and
an STK500 to program the ATMega328P. The main bulk of the code will be converting the
value returned by the encoder and interfacing with the LCD display.
The kernel will contain two different modules: one that samples and the other that
calculates data and outputs to the LCD display. The calculation/output module will run so
long as the sample button is not depressed. This module will average all of the samples
taken from the sample module, calculate the diameter, and display the calculated and
actual diameter to the LCD display. If the kernel has no samples (i.e. upon start up), then
the module will output zeros to the display. (“Calculated Diameter: 0.000 inches.”)
The sample module, which will be triggered by an external interrupt (sample button),
will sample data from the encoder at a given sample rate. It will sample data as long as the
switch is depressed.
f.
User Interface:
FIGURE 4: User interface layout
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FIGURE 5: Example output
FIGURE 6: State diagram for user interface
The user interface will consist of an LCD display, an ON/OFF switch, a reset button, and a
sample button. The device will have two states: SAMPLE and OUTPUT. The device boots up
into the OUTPUT state. When the sample button is depressed, the device will enter the
SAMPLE state where the DDM will take readings from the encoder at a given sample rate.
Once the sample button is released, the DDM returns to the OUTPUT state. In this
state, the device will average all of the samples received while in the SAMPLE state. I will
then have to convert this value into the equivalent “H” value in inches and, using this “H”,
calculate the diameter of the pipe. The DDM will then output both the actual calculated
diameter and the standard industrial pipe size closest to that of the calculated to the LCD
display. An example of the output is provided in FIGURE 5 where the “O’s” are pixels that
are filled in. This information will remain on the LCD display until the reset button is
depressed or the sample button is depressed (returning it to the sample state.)
5
Because the device boots into the output state, the device will output zeros to the
display. For example, it would be identical to that of FIGURE 5 except instead of “11.11” it
would display “00.00.” It would be the same if the user were to press the reset button.
g. Sustainability:
The DDM will operate off of one 9 volt battery which requires no proper disposal
methods. In order to save power consumption, the DDM will have a sleep mode. If the
device is on for a certain amount of time (x amount of clock cycles), then it will put the MCU
into low power mode. The user will have to depress and release the sample or reset button
once, or turn the device off then on in order to “wake” the DDM up.
STANDARDS
NPS – Nominal Pipe Size
A North American set of standard sizes for pipes used for high or low pressures and
temperatures.
DEVELOPMENT PLAN
a. Weekly Schedule:
WEEK #
1
2
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5
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DATES
1/7 - 1/11
1/13 - 1/18
1/21 - 1/25
1/27 - 1/31
2/3 - 2/7
2/10 - 2/14
2/18 - 2/21
2/24 - 2/28
3/3 - 3/7
3/10 - 3/14
3/17 - 3/21
3/24 - 3/28
4/2 - 4/4
4/7 - 4/11
4/14 - 4/18
4/21 - 4/25
4/28 - 5/2
5/5 - 5/9
5/12 - 5/16
5/19 - 5/23
5/26 - 5/30
6/2 - 6/6
6
PLAN
Finish mechanical design
Finish mechanical design
Finish mechanical design
Rotary encoder interface
Rotary encoder interface
Rotary encoder interface
Rotary encoder interface
LCD interface
LCD interface
LCD interface
Dead Week
Spring Break
Buck converter interface
Buck converter interface
Buck converter interface
Hardware design review
Debug/Clean up code
Debug/Clean up code
Software presentation
Code review
Demonstration preparation
Final demonstration
b. Description of hardware/software:
The testing and the design will take place mostly in the Ross Engineering Technology Lab
in ET340 and ET333 on Western Washington University’s campus. The required tools and
software required to complete this project will be Atmel Studio, MATLAB, a digital
oscilloscope, and a soldering kit. Because the computers in the ET340 and ET333 labs do not
contain Atmel Studio, I will run the software off of an external hard drive.
c. Description of demonstration:
To demonstrate the final product, I will have a cardboard presentation board to present
the design, dimensions, and implementations. Also I will have a few (three to five) pipe
cutouts of varying diameter lengths that people will be able to test the DDM on.
ELECTRICAL SPECIFICATIONS
a. Project specifications (as required):
SPECIFICATION
Pipe Diamter Range
Resolution
Accuracty
DESCRIPTION
6" - 96"
hundreths place
.01 of an inch
b. Power requirements:
SPECIFICATION
Rotary Encoder
ATMega328P active
ATMega328P power-save
Nokia 5110
DESCRIPTION
80 mA
.2 mA
.75 micro amps
10mA
The standard 9V battery is typically rated around 400 – 600 mAh. The Duracell PC1604
for example is rated at 500 mAh. The DDM will consume 90.2 mA whilst in active mode and
10.00075 mA in power-save mode. If the DDM were operating with this PC1604 it would
last 5.54 hours in active mode and 50.00 hours in power-save mode. The entire process of
measuring the pipes is estimated to take two hours and is done roughly once a week. I
estimate the DDM to be in active mode for 50% of the time. So by these figures the battery
would last around five weeks.
c. Special environmental requirements:
SPECIFICATION
Operating Temperature Range (Celcius)
7
DESCRIPTION
-10 to 60
PRELIMINARY PARTS LIST
PART
Atmel Microcontroller
OMRON Rotary Encoder 2000 P/R
84x48 Nokia 5110 LCD Module Display
Linear Technology Dual DC/DC Controller
Resistors
Capictors
MANUFACTURER PART #
ATMega328P
E6B2-CWZ6C
PCD8544
LTC3890-1
8
QUANTITY
1
1
1
1
10
10
TOTAL
POWER
45 mW
400 mW
300 mW
250 mW
X
X
995 mW
COST
$3.16
$32.40
$3.99
$6.80
$0.05
$0.05
$47.35