Problem with PIC 16F628A resetting intermittently

[Archangel]

Hi,

. . . Your heating coil draws a lot of current, and I suspect the spurious resets would be happening when the relay releases.

A snubber circuit accross the load might help.

Anand

Wow, it did not occur to me it was an electric resistive heater, I was thinking it was gas . . . Good call.

[hbalit]

Thanks to all for sending suggestions to solve my problem.

I do have a commercial opto isolation module in the circuit and this sends a voltage to the remote contactor coil at the heater.

I have added command to my code to display on a LCD so I could follow the program flow and monitor where the problem occurs.

I have now had more fun for the last 11 hours simulating and watching the program do its work with the actual heater disconnected. (more fun than watching paint dry) Ha Ha.
The program did fail twice in that time and it appears that it goes to the temperature read subroutine and then suddenly resets. The point when this happened was when the temperature just got to the minimum trigger setpoint. My LCD display did not indicate that it left the subroutine and went to the comparison section.

I am going to try battery power but I do not suspect that is the problem as I have a 2A 5V supply that is fed off a different circuit than what the heater is on.

I will keep plugging along.

Harold

[Archangel]

Hi Harold,
What kind of lighting is in the area you are working? Sometimes Fluorescent lights make unshielded PICs behave badly.

[Demon]

Hi Harold,
What kind of lighting is in the area you are working? Sometimes Fluorescent lights make unshielded PICs behave badly.

I didn't know that. What kind of shielding? A metal enclosure?

Robert

[Archangel]

Hi Robert,
I scrapped out a TV a Magnavox that had metal shields around it's CPU chips, they fit under and over them, only the pins were not shielded. Some forum members here have reported this problem in the past. I think breadboards would be esp. susceptible . . Remember RF crawls around on the surface whereas DC goes through a conductor.