> What I was wondering, is there any sort of device that I can
> make/buy that
> I can hook up to my water pump that will 'time' how long it is
> continuously running. Then it sends an alarm after it has
> been running
> continuously for more than a preset length of time?
I don't know of a commercial device, but it shouldn't be too hard to build
something that would do. Basically you just need a counter or clock that
starts at zero when the pump comes on, and sounds an alarm when the
count/time exceeds your threshold.
Here is one example, using the venerable NE555 timer chip:
http://www.sentex.ca/~mec1995/gadgets/555/555ex8.gif
For your purpose, you would substitute a relay coil for the "ID red" LED &
dropping resistor; plus a circuit that detected when the pump was running in
place of the "reset" button (so pins 2 & 4 are grounded when the pump is
off). The alarm delay can be adjusted over a wide range by changing the RC
network on pins 6 & 7. If the pump runs for longer than 1.1RC, the relay
gets activated and can set off whatever you want in terms of lights &
sirens. Probably easier to use a 12v supply instead of the 9v indicated, so
you can use a standard 12v relay.
-- Randall
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