I have several products that use PICs in industrial machinery - which have
been doing quite well except for the rare, but unpleasant instances below.
These PIC based designs have replaced other commercially available
controllers and PLC's and the like. I have noticed in a couple of machine
installations what seem to be brown outs and resets. I have had similar
occurrences back in the 'old' days when using PLC's - If the building wiring
is weak, or if an electician a bit careless, someone will turn on a large
machine at one end of the building and my PIC, like the PLC's will lock up.

I can tell customers that they need a small UPS for a PLC in this
environment, but it won't cut it with my own design...the idea was to
improve the process while SAVING $$.

I figure this must be a fairly common thing to deal with. I am a bit
surprised because these boards are phase angle controllers and have been
hardened (via snubbing, gating methods and filtering and decoupling) to
withstand the worst noise from the AC switching at peaks.
The lock-ups happen when the AC line is lower than normal, so I have changed
to a(n) LDO Regulator (Thanks, Olin, for your suggestions).
If these events still occur, I am left to conclude that there must be some
interruption of the line of significant duration.
Where might I look for strategies to deal with such a thing? I need 4.5V
<200mA to keep the whole thing running for the duration. Having no
experience with such things as super caps, I am wondering if this is a good
app for one....

C

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