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SAE Formula Car Display and
Data Acquisition System
“SAEDAQ”
Caleb Davison
Phil Jacher
George Kontos
Advisor: Mr. Gutschlag
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Overview
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Summary
Measurement Strategies
LabVIEW User Interface
Microcontroller
LCD Screen
Wireless Chips
3
Overview
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Summary
Measurement Strategies
LabVIEW User Interface
Microcontroller
LCD Screen
Wireless Chips
4
A Typical Car…
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SAEDAQ Summary
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Society of Automotive Engineers Formula
One racecar
Data recording
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wheel speed
engine rpm
oil pressure
oil temperature
coolant temperature
Data will be transmitted to the car’s
dashboard and an off-track laptop
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Previous Works
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Project has been attempted several times
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Never been able to coordinate with MEs
Most recently last year with Justin Peters
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Using different MCU, upgraded wireless chips
New dashboard design
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High Level Block Diagram
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Overview
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Summary
Measurement Strategies
LabVIEW User Interface
Microcontroller
LCD Screen
Wireless Chips
9
Temperature and Pressure
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Temperature sensor
(0-300 degrees
Fahrenheit) x 2
Pressure sensor
(0-100 psi) x 1
Requires supply
voltage (12V)
Outputs current
(4-20mA)
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Sensor Measurement Circuit
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From datasheet:
ZLmax=(Vs-9.6)*50
Vs=12V from car
battery,
ZLmax =120 ohms
Issue: at 20mA, A/D
voltage will be only
2.4V
Solution: Adjust A/D
resolution (0-2.56V)
VL
ZL
A/D
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A/D Method - Temperature
A/D Res (2.56/255) Volts
Sensor Output
(mA)
uC Bit Number
Temperature (Fahrenheit)
0.48
0.49
0.5
0.51
0.52
0.53
0.54
4.00
4.08
4.17
4.25
4.33
4.42
4.50
48
49
50
51
52
53
54
0.00
1.56
3.13
4.69
6.25
7.81
9.38
2.34
2.35
2.36
2.37
2.38
2.39
2.4
19.50
19.58
19.67
19.75
19.83
19.92
20.00
234
235
236
237
238
239
240
290.63
292.19
293.75
295.31
296.88
298.44
300.00
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Linear Based Method
Temperature vs. A/D Value
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350
y = 1.5625x - 75
300
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Temperature
250
200
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150
100
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50
0
0
50
100
150
200
250
Temp=(1.5625*A/D
Value)-75
Attempt 1: Temp=((A/D
Value*3)/2)-75
Attempt 2: Temp=((A/D
Value*1563)/1000)-75
Solution: Look up table,
use memory available
300
A/D Value
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A/D Method - Pressure
A/D Res (2.56/255)
Sensor Output
uC Bit
Volts
(mA)
Number
0.48
4.00
0.49
4.08
0.5
4.17
0.51
4.25
0.52
4.33
0.53
4.42
0.54
4.50
2.34
2.35
2.36
2.37
2.38
2.39
2.4
19.50
19.58
19.67
19.75
19.83
19.92
20.00
Pressure (PSI)
48
0.00
49
0.52
50
1.04
51
1.56
52
2.08
53
2.60
54
3.12
234
235
236
237
238
239
240
96.87
97.40
97.92
98.44
98.96
99.48
100.00
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Linear Based Method
Pressure vs. A/D Value
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120.00
y = 0.5208x - 25
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Pressure (psi)
100.00
80.00
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60.00
40.00
Temp=(0.5208*A/D
Value)-25
Attempt 1: Temp=(A/D
Value/2)-75
Solution: Look up table,
use memory available
20.00
0.00
0
50
100
150
200
250
300
A/D Value
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Engine RPM Measurement
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ACI Hall-effect current
sensor
TTL output
Induced supply power
Meets amperage
range
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Overview
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Summary
Measurement Strategies
LabVIEW User Interface
Microcontroller
LCD Screen
Wireless Chips
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LabVIEW Interfacing: Front Panel
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LabVIEW Interfacing: Front Panel
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LabVIEW Interfacing: Front Panel (cont.)
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RS232 communication protocol
Complete control over settings
Data logging feature
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LabVIEW Interfacing: Front Panel (cont.)
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LabVIEW Interfacing: Front Panel (cont.)
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Pressure and temperature updated in real
time along with engine RPM and speed
Warning lights indicate dangerous levels
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LabVIEW Interfacing: Front Panel (cont.)
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LabVIEW Interfacing: Front Panel (cont.)
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Data vs time displays operate independently
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LabVIEW Interfacing: Parallel Computing
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Overview
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Summary
Sensors
LabVIEW User Interface
Microcontroller
LCD Screen
Wireless Chips
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Microcontroller: Amtel ATmega
128 MCU
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16 MHz clock
8 A/D converters
Voltage regulator
(5.5-15V)
Dual UARTS
Additional power and
ground connectors
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Programming Phases
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A/D Converter
RS-232 Interface
RPM Counter
Touchscreen
All Together
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Programming Phases
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A/D Converter
RS-232 Interface
RPM Counter
Touchscreen
All Together
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A/D Conversion
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Records oil pressure, oil temperature, and
coolant temperature
A/D inputs: 0-2.56V
Sensor voltages: 0.48-2.4V
Scaled into single byte value
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A/D Conversion
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ADC clock machine cycle: 8us
1st conversion: 200us
Normal conversions: 104us
Three conversions: 312us
Vin * 255
ADC 
Vref
Vref = 2.56 V
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Programming Phases
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A/D converter
RS-232 Interface
RPM Counter
Touchscreen
All Together
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RS-232 Interfacing
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Previous experience with transmit/receive
Stair step progress:
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Polling
Interrupt driven
Timer based
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RS-232 Interfacing
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Hyper Terminal problems
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Incorrect Hyper Terminal settings
ASCII Setup – echo typed characters locally
Transmitting/Receiving settings:
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9600 baud
8 data bits
1 stop bit
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Example RS-232 Communication
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Receive key press
from computer
ASCII ‘F’ sent back to
computer
Hyper Terminal
displays appropriate
values
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Example RS-232 Communication
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String based
communication with
timer
Sends “1abcde” every
5 seconds
Practical application
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Programming Phases
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A/D Converter
RS-232 Interface
RPM Counter
Touchscreen
All Together
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RPM Counter
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Example simulation
Set up basic pulse
counting program
100ms (10 Hz)
sampling period
Counts rising edges
30 Hz Pulse Input
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RPM Counter
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Problems with 16-bit counter
Had to use external interrupts
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Rising edge triggers interrupt
Counter increments
Inefficient
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Programming Phases
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A/D Converter
RS-232 Interface
RPM Counter
Touchscreen
All Together
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Touchscreen
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ASCII protocol
CRC protocol
Used XON/XOFF to simplify
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XON/XOFF Communication
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ASCII Protocol
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Set byte variable 1 to
0xFE
Set IR word variable 0 to
0x02C9
0xD5
0xD6
0x30
0x31
0x46
0x45
‘0’
‘1’
‘F’
‘E’
0x30
0x30
0x30
0x32
0x43
0x39
‘0’
‘0’
‘0’
‘2’
‘C’
‘9’
Opcode
Internal RAM address
Internal RAM value
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Jump to Page Function
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Does not use the normal ASCII protocol
Reads in hexadecimal format
Jump to page 0x103:
0xA0
0x02
Command
0x01
0x03
0x5A
Page # MSB
Page # LSB
checksum
Opcode
Internal RAM address
Internal RAM value
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Calculating the Checksum Value
0xA0
0x02
Command
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0x01
0x03
0x5A
Page # MSB
Page # LSB
checksum
X=0xA0+0x02+0x01+0x03=0xA6
The sums of the LSB must be 0xNN00
0x100-0xA6=0x5A
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Programming Phases
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A/D Converter
RS-232 Interface
RPM Counter
Touchscreen
All Together
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All Together
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Software Flowchart
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Overview
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Summary
Sensors
LabVIEW User Interface
Microcontroller
LCD Screen
Wireless Chips
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Touchscreen
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Amulet Technologies
GEMStudio
µHTML
9600 Baud
Resistive technology
LCD GUI from 2010 Project
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Touchscreen
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Design
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Numerical displays
Warning indicators
Inter-widget communication
Multiple pages
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Touchscreen Design
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Touchscreen
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Widgets
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Function Buttons
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Calls a function when hit
Numeric Fields
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Pulls the values from bytes in the Amulet’s
internal RAM
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Touchscreen
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Communications with microcontroller
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ASCII protocol
CRC protocol
Amulet as slave
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XON/XOFF protocol
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Overview
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Summary
Sensors
LabVIEW
Microcontroller
LCD Screen
Wireless Chips
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Wireless Chips
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Chipcon CE2500M
Voltage Regulator
RS-232
Packets
Infinite transmission
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Wireless Chips
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Aerocomm AC4790
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Aerocomm Software
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Future Work
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Noise suppression circuitry
Enclosures
Sampling rates
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Temperature, RPM, land speed
Land speed calculation
Support documentation
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Schedule
Week of:
Caleb
Phil
George
12/5/2010
finalize parts list with mechanical engineers
winter break
order parts, research
1/23/2011
program temperature sensor
research touchscreen software
design interface for LabVIEW
setup
1/30/2011
program pressure sensor
work on example programs
program LabVIEW for receiving
data
2/6/2011
program wheel speed sensor
work on design options for
touchscreen GUI
test LabVIEW for receiving data
2/13/2011
program displacement sensor
design GUI for touch screen
work on sensor circuitry
2/20/2011
program and combine modules
design GUI for touch screen
make sensor test bench
2/27/2011
program and combine modules
finalize design and construct
GUI
make sensor test bench
3/6/2011
set up analog to digital
converters
work on communications with
microcontroller
work on LabVIEW datalogging
3/13/2011
spring break
3/20/2011
implement counters
finalize GUI / communications
with microcontroller
work on LabVIEW datalogging
3/27/2011
program microcontroller to
transmit data to LabVIEW
finish all touchscreen
elements. start on wireless
finalize LabVIEW design and
sensor circuitry
4/3/2011
interface all devices together. work on wireless devices
4/10/2011
interface all devices together. work on wireless devices
4/17/2011
work on wireless devices. documentation/finalization/final report/presentation
4/24/2011
documentation/finalization/final report/presentation
5/1/2011
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Questions
62
Calculating Timer Value for Pulse
Counter
f OCnA
16 Mhz

N 1  OCRnA 
1
16Mhz

0.1 641  OCRnA 
OCRnA  24999  0h61A7
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