I am just starting to use pic devices. I have just designed a PCB using a
PIC16c55 as a logic controller for a system controling three phase contacors.
The PCB opperates correctly on the bench, but once connected in it's real
situation, it starts to reset almost every time one of the coils for the
contactors comes in.

I am not sure, but I think my problem may lie in the way I have connected
the periferal components to the PIC. For example I am not sure of values
for a reliable power on reset circuit. It is hard for me to know exactly
what is causing my PCB to reset, but an interesting point I noted was
that a 'Power-On' LED connected directly to the 5v suppy flickers sometimes
when the coils in the system power down, but if I remove the PIC from the
board it no longer flickers with the coils. It's almost as if the PIC is
somehow having an extream loading effect on the power supply (but only when
there are voltage transients around).

Could anyone give me any tips as to the configuration of a reliable set of
components external to the PIC.

Or, could anyone point me in the direction of information (diagrams) to
let me know what a good setup is.

Any assistance would be greatly appreciated,

Thanks,

Wayne G Boyd.