I don't know if anyone is going to be able to help me on this one, but i'm going to ask anyway. I must be making a fundamental error of some kind in this circuit. I don't have a schematic, but I will describe it as best as I can.
I want to control a 3 phase AC motor with a low voltage momentary push button switch. I want one push to turn it on, and the next off.
I cheated and programmed a PIC to do this for me. I have the input pin pulled low and am using 5v+ though the push button.
The pic switches a darlington, that switches a 12v relay, and that switches a 3 phase contactor with a 24v AC coil. I have a 12/24v transformer to power the switching. From the 12v I have a bridge rectifier and a filter cap and 7805 to power the PIC.
On proto board the pic and darlington work flawlessly switching an LED. Mounted in the enclosure with the relays, it will switch the 12v relay perfectly if the 3 phase contactor is unhooked or if I hold it on via direct connection from the transformer.
When its hooked up things go bad. It works fine 50% of the time and the other half of the time its like it begins to switch the 12v relay, and then releases. It just sort of bounces on and then back off. I took the PIC out of the circuit and manually jumped 5v on the darlington and that works fine too, so I know the problem in in the PIC. I lengthened the de-bounce delay in my program, thinking maybe a voltage was being induced somewhere in the circuit causing it to cycle. It didn't really help.
I think it has to have somthing to do with the coil in the 3 phase contactor
Does anyone have anything I could check or try? Everthing was working so good up til this point