At 10:57 AM 1/25/2006, andrew kelley wrote: >Hello all, > >I have a solid state relay controlled by a 'c508 which is powered from >a simple power supply (transformer, rectifier, regulator with 470uF >cap on input and 10uF on output). We have a microwave which when you >open or close the door generates +/- 0-8v spikes on the power *to the >micro*.. We think that these power glitches are causing RAM data to >change and the PC to change and alter the execution of further code. Hi there, Andrew. The spike magnitude suggests strongly that you have a measurement problem. I believe the spikes are causing your problem but I'd like to ask exactly *how* you connected the scope probe when measuring them. I'm assuming that you used the standard (long) ground from the scope probe? If so, try this: your scope probe should have a bare shield area right near the probe tip. Wrap a couple turns of bare #22 or #24 wire around that shield area and twist the free ends of the wire loop together TIGHTLY so as to make a short, stiff lead. Use that wire to make the shortest possible connection to your 0V rail right at the 12c508. Solder the free end of your new ground lead to the 0V pin if you can. Assuming a standard Tek scope probe, that means that the ground lead should be no longer than 3/16" and still allow the probe tip to reach the +5V rail at the PIC. Now measure the spike amplitude at each of the PIC pins. Keep that ground lead as short as is possible. The spikes might be coming in on the VDD / ground leads - or they might be coming in somewhere else. Susceptibility to sharp, fast transients can be the devil to track down but it is almost always possible. Good luck! dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 21 years of Engineering Innovation (1984 - 2005) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist