CL> Situation: Found out that the home builder had put in AC smoke detectors
CL> that weren't gang-trip. I installed new gang-trip ones, and decided to
CL> put another in the detached garage.
CL> Gang-trip 3-wire type (hot, neutral and trigger).
CL> Occasionally, work in the garage (soldering something, starting the lawn
CL> tractor etc) will set off the garage alarm which immediately fires up
CL> the others... Annoys the rest of the family no end.
CL> Been thinking of putting a switch into the garage alarm's supply feed.
CL> Ideally, it'd be a normally-closed timer that when "enabled", it'd
CL> disable the garage alarm and gang trip feeding the other alarms until
CL> the timer ran out.
CL> Has anybody else done something like this? Suggestions?
CL> I could put a double-pole switch in (to cut the hot and neutral), or
CL> even a single-pole (just cutting the hot should work), but these
CL> are battery backup units, so I suspect that wouldn't work...
CL> So maybe the best I can do is disable the gang-trip with a switch.
CL> Are there any cheap "normally closed" mechanical timers?
The heat detector suggested by others is probably a better idea but if
for some reason you prefer to use the smoke detector how about
something like a bathroom fan timer (60 minute?) powering a SPDT
relay? You smoke detector is wired to the NC terminals. When you're
about to make smoke turn the timer on, which pulls in the relay
contacts, opening the circuit. At the end of the timer cycle the
power to the relay is cut off, automatically resetting your smoke
detector. Probably need to pull the battery in the garage smoke
detector else it will scream, but that might cause the others to
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