"DaveC" wrote in message
al.net...
So the answer is... no.

If power fails at the remote site, so does the control circuitry and
its
power. So a traditional delay relay won't work.

The relay, powered by mains, simply opens the wireless sensor's sense
circuit
when power goes away. I just want it to do so after waiting a few
minutes to
see if power comes back on.

The alarm isn't for security purposes, just for letting those
responsible
know that certain things have occurred, one of which is power fail.
The
sensor is a wireless device run on a lithium battery, and is a
packaged deal
so has no spare power available. The relay's not near the alarm CPU,
so that
power isn't available, either.

Suggestions for a simple mains-powered circuit that will open a pair
of
contacts about 5 minutes after de-energizing? If it's to be
battery-powered,
it needs to be super-low drain. I rather keep battery replacements
down to
every 2 years, at most.

An idea that just struck me: the presence of mains power could keep
this
circuit de-energized. When power fails, the battery is connected to
the
circuit which starts the countdown. When zero is reached (ie, 5
minutes have
passed), a pair of contacts would open. And the energizing circuit
(triggering these contacts) would only have to be a one-shot; once the
alarm
is triggered, the circuit could de-energize. That way the battery is
utilized
only briefly, during power-fail situations. How might I construct such
a
circuit?

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

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I never cease to be amazed at the questions asked in this NG from people
who do not have a clue from grade school experiments about electronics
but want to design or modify industrial situations where some manager
should be putting up the money to employ a competent engineer skilled in
the particular area.

Relying on poorly informed advice is asking for trouble and a sure
course to the courts for a damages claim.
--
John G

Wot's Your Real Problem?