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From: cyamamot@nunki.usc.edu (Cliff Yamamoto)
Newsgroups: sci.electronics
Subject: How could I make a delayed one-shot?
Keywords: delayed, one-shot, simple, chips
Message-ID: <4689@merlin.usc.edu>
Date: 9 Aug 89 15:03:15 GMT
Sender: news@merlin.usc.edu
Reply-To: cyamamot@nunki.usc.edu (Cliff Yamamoto)
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Organization: University of Southern California, Los Angeles, CA
Lines: 33

Greetings,

I'd like to thank everyone for their replies on lighting bulbs with TTL.  Now
that I know how to calculate all that stuff, my little circuit is quite happy
(myself included)!

Now I'm trying to whip up something a little different.  What chips would you
use to make a delayed one-shot like this :

normally high input (+12 volts)
-----------+		  ______________	 ______________
	   | goes low	 |		|	|	       |	pulse
(0 volts)  +------------>| .1 to 1 sec. |------>| .5 sec pulse |------> output
			 |______________|	|______________|
			 wait after input	triggering the one
			 goes low before...	shot to generate its pulse

(Note : when the one-shot generates its pulse, the input to the delay circuit
	will go from low back up to high.  The one-shot pulses a solenoid, the
	input is from a microswitch )

I'll probably use a 555 for the one-shot (since it can sink/source 200mA) but
the delay circuit is a different matter.  The timing is not too critical.  I
don't really want to clock any kind of divide-by-n gizmo unless it's all on a
chip or relatively simple to wire.  I'd rather have some simple RC delay and a
multi-turn pot to get some granularity for setting the delay.

Any pointers (especially on any chips that can do this in one package) would be
appreciated.

Thanks again to all you friendly hobbyists!

Cliff Yamamoto