Tire Pressure Sensor

The pressure is determined by the formula, <m>P=0.145*{{{ADC/2^10}-0.04}/0.0012858}</m> where ADC is the value from the 10-bit DAC and P is the pressure in PSI. The pressure sensor is ratiometric with respect to Vdd which makes it easy to interface to the PIC. Instead of the LCD display the finished project will use the 7-segment display module to make it easier to read under different lighting conditions. Also, I have not been able to locate a small, backlight display, or even a small single line display that is inexpensive.

Prototype

Parts

Part# Description Source Cost
MPX5700DP-ND0-101.5PSI Pressure sensorDigikey$16
2 Ft 1/4ID hoseHome Hardware$1.50
2 crimp style hose clampsHome Hardware$1.60
Barbed hose connectorHome Hardware$1.19
Compression fittingHome Hardware$1.95
Street ElbowHome Hardware$2.29
Barbed hose connectorHome Hardware$1.19
Click on air chuck for valve stem Princess Auto$3
1/8NPT tank valvePrincess Auto$2.50
Total $33

Development

Here are the calculations I did for the module using a spreadsheet to graph the transfer function, then working out the math to something which can be easily done in assembly.

MPX5700 Datasheet

 
projects/electronics/tirepressuresensor.txt · Last modified: 2014/11/13 10:50 (external edit)
 
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