Hi everyone,

I’m planning on building few gismos for automotive application based on PIC microprocessors and I will need to interface with some custom sensors and other modules. I will be dealing with ADC input, and digital inputs and outputs. Because this will be a long term step by step project I would have used and unused PIC I/Os for expansion.

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).

I have some experience and I got good results potting the PCBs with different epoxy type products which will take care of the mechanical aspect. I will also make sure I will filter my 12 V in as well as possible along with the 5 V line and the mandatory decoupling capacitors next to VDD – VSS pins.

What I’m looking for is some kind of protection so my I/Os don’t get randomly zapped or fooled by EMI. I’m not dealing with extremely fast signals so I guess just a T like configuration, limiting resistor series + capacitor to ground + limiting resistor series might do. Should I go to the extreme of using voltage suppressors?
Also, how do I deal with an ADC input without messing up the input voltages (I expect 0 – 5 V full scale) and without loosing resolution?

Any input will be appreciated.

Nick