Design

The sensor management board implements all the circuitry necessary to do level adjustment on the sensors. This allows the PIC to simply read the port, looking for a 0-5V signal, spanning the range of the sensors that we are interested in.

The pressure sensors already take care of this themselves. Unfortunately, the pressure sensors we started with only dropped down to 15kpa. This will bottom out once we reach about 20km above sea level.

The temperature sensors give us a read of -0.55V to 1.5V based on a temperature range of -55 to 150 degrees C. We needed to push this up to 0-5V and also adjust the range as we are not likely to see temperatures above 50 degrees C. We are probably not going to see temperatures above 40 either, but might as well keep the range somewhat open. This adjustment is performed with 2 opamps.


 


Schematic



 


Layout



 


Eagle Files

Schematic
Layout