Subject: please help with controller problem
By: tim (IP: 192.250.34.*)
Written on: 20-03-2006 15:11
I thought I had it working but lost ability to control via trim pot.
I had built a 2 zone system using a Radio Shack 1500mA dc converter for 12v supply
Common + side connection to: fan+, two thermistors, and a 12v led indicator assembly.
Common - side to: Source side of 2 MOSFETs and mid lead of trim pot.
Seperate connections from each NTC, Back lead of 1 pot, and gate of 1 MOSFET.
Seperate connections from each MOSFET drain to fan - and led.
Seemed to work well at first, each fan (actually a set of 3 fans on each circuit), and led reacted as expected to temp changes on the respective ntc in the circuit, although I did notice a bit of cross effect, ie; turning one pot seemed to have some effect on the other circuit.
I had each ntc wired to a 3/32 plug and jack, and after plugging and unplugging a couple of times, I could no longer adjust via the pot. I checked out the pots and both showed infinite resistance with no effect on turning the adjustment. This happened twice, replacing the pots between each attempt.
I obviously have no knowledge of electronic components, so I am wondering if there is an issue with the connections the way I am attempting to wire. Is there some isolation needed between the circuits?