No news is good news; more news

Well, I replaced the ground fault interrupt outlet that the sump pump was plugged into a month or two ago, and I haven’t heard a peep out of the alarm since. So that must have been the culprit all along.

I’m still glad the alarm is there, because if any new problems crop up (or the new GFI dies again for some reason), I’ll know.

And since then, our other sump pump - the one at our rental property - blew a circuit breaker after the outlet hose froze up outside, and then the basement filled up with water almost to the danger point. Can’t have that happening again. So, I now have a new batch of parts on order to make another sump pump alarm!

Should be fun. The only change I plan to make to the original circuit, apart from minor construction changes due to different part availability, is to use a more appropriate Zener diode this time - 3.9 V instead of 5.1 V. The voltage seen by the PIC is the battery voltage minus the Zener voltage, so this should give me a solid 5.1 V on the PIC. At the clock frequency I’m using, the PIC was fine with the 3.9 V it was getting in the previous version, but doing it correctly should allow it to work slightly longer as the battery ages and its output voltage drops.