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From: arnief@tekgvs.LABS.TEK.COM (Arnie Frisch)
Newsgroups: sci.electronics
Subject: Re: A pathetically simple question...
Message-ID: <6027@tekgvs.LABS.TEK.COM>
Date: 29 Sep 89 20:40:35 GMT
References: <1989Sep28.122217.26867@watcsc.waterloo.edu> <4377@wpi.wpi.edu>
Reply-To: arnief@tekgvs.LABS.TEK.COM (Arnie Frisch)
Distribution: sci.electronics
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 15


To build a reproducible time delay of several seconds to 
a minute - or more - a good approach is to do it digitally using
CMOS.  Build an inverter based oscillator out of two resistors
a capacitor and two inverter sections (any good CMOS application
manual will show how).  Follow this with a multi-stage counter.
The counter will have to be reset at power on - This will take a 
diode, a capacitor and a resistor.  Limiting yourself to 1 uf
capacitors and 1 meg resistors and using a seven stage counter IC,
you should be able to get delays up to 300 seconds.

I don't do schematics for free!

Arnold Frisch
Tektronix Laboratories