Quote Originally Posted by Joe S. View Post
I have some ideas,
I would like to see the schematic and your code configs, also part # of the snubber diode. I am thinking . . . Diode too slow . . . Not hooked up right . . . brown out PIC due to reverse EMF, remember the back voltage from that relay coil and motor is several hundred volts, also make sure the PIC is properly bypassed on it's power pins with .01uf and a 10uf, you may need to run separate power lines from the battery for the load and PIC circuits.
Diode is 1N4007. I was indeed wondering about diode speed, since these are the cheapies from Radio Shack. I also put a small cap between the transistor base and ground, to slow down the fall time of the output and reduce the back EMF, too.

Forgot to mention - motor has built-in supression, however the resets occur even with the motor disconnected and only the relay coil active.

PIC is bypassed well, with ceramic cap directly under socket, and electrolytic at the voltage regulator.

I did some further experimintation yesterday, and found out that the relay will cause a reset, even when not connected to the circuit. In other words, with the control wire from the board to the relay coil neg terminal unhooked, if I touch a ground wire to the relay coil (click the relay), the controller will sometimes reset. This is without the motor connected to the relay.

I then took a "snap-on ferrite choke" and wrapped the harnss to the control board through this choke, and the problem is gone.

Here is the schematic (sorry for the hand-drawn schematic - I am not a professional designer by any means!)



The power supply works by taking ignition key switched power through the indicator lamp, through a diode and into the 7805 regulator. This is enough to start the CPU. The first thing the program does is turn on the power hold-up output (pin 10 on CPU) so that it will maintain power when the indicating lamp is grounded by the indicating lamp output. The program monitors voltage at the indicating lamp circuit to know when the car's ignition is on or off, and powers off the power hold-up circuit several minutes after the car is switched off.

I bypassed this and had the circuit connected to stay on constant, and the resets continued so I don't think it is in my power control circuit.

I think the capacitor added to the base of the relay drive (not shown) and the ferrite choke have it fixed hopefully!

Thanks,
David