>>I have attached a PDF of my input circuit.  C1 is 1uf C2 is 33pf C3 is
>>1000pf R1 is 500ohm and R3 is 4.7K.  This circuit seems to work well
>>on my old design but I do not have a PCB version of my PIC project to
>>test it on yet.  I do have a wire wrapped version which fails
>>miserably.
>>
>>


PIC's, I have found, do not like working in high EMI environments.
Ignition systems are a big source of this. It may(?) be that the PIC is
not false triggering, but the core of the PIC is being upset by being
"near" the ignition system and therefore cannot run the code correctly.

I got caught with this big time with my programmable ignition, until I
realised the problem.

Sheilding the PIC, and the wires running into it, may help.

If you doubt this, try having a simple LED flash program and place the
PIC near an operating spark plug or ignition coil. You'll probably find
that the LED flashes erratically.

Unsuppressed spark plug leads (copper cored), also play havoc with PIC
operation.

Remember the interference shown on your TV when an old lawnmower starts
up nearby.

regards

Tony

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