On Wed, 6 Dec 2006 12:43:39 -0800, "Bob F"
wrote:


wrote in message
.. .
"Bob F" wrote:

wrote in message
.. .
I've always had mechanical timers for things like bathroom fans--turn
it on for 30 minutes of wind tunnel to exhaust condensation; it turns
off at the end--but now I'm looking for one that has the opposite
effect. I want the circuit to be on all the time except when I turn
the timer to (say) 30 minutes and it counts down. After 30 minutes it
should re-connect the circuit.

Any suggestions as to what I should look for? BTW it's not going to
switch more than 100 watts @ 110V, maybe even as little as 5 watts.

Find a normally closed or double throw timer switch, or control
a normally closed contact on a relay with a standard timer.

OK, in the meantime I've been searching google and I find:


http://item.express.ebay.com/Industr...mdZExpressItem


---sheesh!---

which seems to fill the bill at a reasonable price.

As to what I want it for...

I'm making some smoke-generating foodstuff in the kitchen and this
piercing unpleasant noise which can't be shut off shatters the
tranquility of the neighborhood necessitating a trip to the load
center to shut off the smoke detector circuit which of course you
forget to turn on again when the smoke has cleared. So...

That 30-minute timer activated before the smoke-generating cooking
will prevent the noise but return the system to alarm-ready state in a
reasonable time without further intervention on my part.

It sounds like you are on the right track.

Bob


'course, if you installed a vent-hood that worked,
you wouldn't have to sabotage the alarm system at all.