Fluctuating digital inputs

[Demon]

So you just have a resistor and LED on every line amd that's it?

That could help diagnostics in case the keypad/display circuit acts up.

Robert

[Dave]

Robert, I don't know what you mean by a resistor and led on each line. I am talking about all of the sensor loops, and individual sensors coming into the control board from some distance away. Having an additional led in series with each of the curcuits would also be an ideal way to visually diagnose the system externals though. What I was talking about was using something like a constant current diode or what I used is a LM317 in a TO-92 package and a resistor configured as a current regurator of 20 Ma. in each of the source circuits for the individual sensor circuits and the loop circuits. They were all powered by the 12 volt power supply.