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In article <4377@wpi.wpi.edu> reynhout@wpi.wpi.edu (Andrew Reynhout) writes:
>
>   Help!  This is an amusingly simple question, but I've been working on it
>for some time now, and can't come up with an answer...
>
>   I need a circuit that will, on application of power, cause a delay of 5-20
>seconds before allowing current to flow through (a different part of the circuit)
>   Basically, it should take, say, 12v, wait 10 seconds, then trip a relay.
>It's for an alarm circuit.  (I didn't see much point in paying $159 for $30 of
>components and a few hours of work.)
>   I tried a deceptively complex setup with a FET and a timing cap and all sorts
>of other nasty things, but I can't get ANYTHING out of it.

Look in a catalog for an Amperite Delay Relay.  They come in the same package
as the thermeonic high-voltage-depletion-mode-JFETs (a.k.a. Vacuum Tubes),
and are just a heater and a pair of bimetalic contacts.  They come in 
6v, 12v, 24v, 110v and 220v, and in times ffrom 1 second to 3 minutes, 
normally open ort normally closed.
the part number format is obvious:
     <voltage><contact style><time in seconds>
         6NO180= 6v NO 3 minute
        12NC1   12v NC 1 second
        110C30  110v NV 30 second
Note that the heater can take DC or AC, it doesn't care.  I've seen both
octal format and 9-pin-miniature versions.  At the surplus store they are
in the $1 region.  I saw them new in a Newark catalog a couple of years ago.

Mike Morris                      UUCP: Morris@Jade.JPL.NASA.gov
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