Temperature and Pressure Control using the


Louis Mo

Stephen Yu


This project involves the implementation of control and monitor for dual processes. The variables monitored are pressure and temperature. The input control is a 16 button keypad and the output is monitored in a 16 character LCD The device can be widely deployed as a cheap solution to room and automobile climate control automation.

Assembly code for device



1. Display Pressure or Temperature

20° C and 30° C.

2. Temperature can be controlled to any of the displayable threshold with approximately +/- 2° C control range.

3. When Pressure is selected as LCD output, temperature is monitored every 20 read cycles or approximately 70035 m secs.

4. Pressure change alarm LED is flashed when the increase in pressure is past 5 PSI within five read cycles or approximately 35 m secs.


Hardware: 1 AT90S8535, 1 STK200, 1 RCM2034R LCD,

1 16 button keypad, Lucas NovaSensor NPC 410 pressure sensor,

1 NTC GE 76 thermistor

Wiring Scheme:

Circuit Specification:

Clock rate 4Mhz AREF 4.096 Volts

The following graph depicts the linearization relationship for the GE 76 thermistor:

Temperature^2 VS Resistance

Voltage step per PSI increase for the Lucas Novasensor:

4.1667mv per PSI

DC offset from output of NPC-410


Table of temperature with respective voltage.