PICs and harsh environments

[erice1984]

I recently made a circuit thing, it worked great in my "lab" environment but once I put it in the car, it made this high freq ringing, extremely annoying and took it out. In the mean time I am trying to figure out what I 'left' out of the build.

I would say yes to the capacitors... this I noticed from looking at other schematics and re-reading what I should have already known about it.

I am curious to see what advice is given from the seasoned vets, /subscribed

[aratti]

The question I have is does anyone recommend a particular configuration of the I/Os so they are safe from the extremely harsh environment on both aspects: electrical and mechanical / chemical (vibrations, water and (or) other fluids).

Potting the PCB with epoxy products will solve the mechanical and chemical problems, as far as the electrical isolation is concerned, use optocouplers TLP504 for digital I/O and HCNR200 for all your analog staff.

Al.

[Nicmus]

Hi Al,

Thank you for your input.
I've been using optocouplers with good results before but had never used HCNR200 for analog I/Os. I'll give it a try.

Regards,

Nick

[Ioannis]

And a regulator for your logic/analog/digital circuits. Do not connect anything directly on +12V. Instead use lower Vcc for analog or digital about 8-9 Volts and 5 or 3.3 for the controller. So a regulator with large enough capacitors will almost eliminate your problems along with the other suggestions by Al and erice1984.

I once (and more inexperienced in electronics) had a major problem with C-MOS used as an alarm in my dad's car. Every time the alarm was triggered, the horn was generating so much electrcal noise that reset all circuits. A 7808 saved the alarm from the trash.

Ioannis