Overview:
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.
Functionality:
1. Display Pressure or Temperature
- Pressure will be displayed when button A is pressed.
- Temperature will be displayed when button B is pressed.
- Temperature is displayed in intervals of five Celsius from �20° C to 20° C and 30° C to 80° C.
- Displays the closest to 20° C, 23° C, 25° C, 28° C when in the range between
20° C and 30° C.
- Pressure will be displayed in lb/inch2 from 0 to 30 PSI in intervals of one PSI.
2. Temperature can be controlled to any of the displayable threshold with approximately +/- 2° C control range.
- When Button D is pressed, user will be prompted to enter the temperature range desired.
- There are 24 temperature ranges available as shown in table 1. These ranges are selected by punching the range number in the keyboard.
- Temperature control has a three stage differential sensing scheme. When temperature is within approximately 2° C within desired temperature range, then a lower intensity fan is deployed. When temperature is approximately between 2° C to 4° C within the desired range, a higher intensity fan is deployed. When the temperature discrepancy from the desired temp is more than 4° C then the highest fan intensity is selected.
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.
For more detail: Temperature and Pressure Control using the AT90S8535
