Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!pasteur!cory.Berkeley.EDU!atn
From: atn@cory.Berkeley.EDU (Alan Nishioka)
Newsgroups: sci.electronics
Subject: Re: Latching Relays
Message-ID: <17419@pasteur.Berkeley.EDU>
Date: 20 Sep 89 22:42:50 GMT
Sender: news@pasteur.Berkeley.EDU
Reply-To: atn@cory.Berkeley.EDU (Alan Nishioka)
Organization: University of California, Berkeley
Lines: 19


For a friend's mechanical engineering project I needed a circuit that
latched.  I built a circuit using two SPDT relays in which power through
one coil closed a switch which energized the second coil which closed a
switch which energized the first coil, or something like that :-)  Kinda
like an RS latch.  This worked fine for my application, except there was
a condition where if the wrong switch was closed, the system would
oscillate.

Does a simple device exist which does this sort of thing?  (ie. Is there
a better way to build a circuit with memory?  (perhaps with transistors))
I didn't want to use a 7474 for simplicity and power supply reasons.
 
At the time, I looked at some of the "latching relays" I had heard about.
These apparently have two coils, and a pulse to one coil latches the 
switch one way, while a pulse to the other coil latches the switch in the
other state.  This wouldn't have been useful to my application.

Alan Nishioka            atn@cory.berkeley.edu            ...!ucbvax!atn%cory