Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!think!ames!ucsd!ucsdhub!esosun!seismo!uunet!iscuva!jimc
From: jimc@iscuva.ISCS.COM (Jim Cathey)
Newsgroups: sci.electronics
Subject: Re: 1Hz signals
Message-ID: <2080@iscuva.ISCS.COM>
Date: 17 Oct 88 16:36:55 GMT
References: <2006@lll-lcc.llnl.gov> <931@ccnysci.UUCP>
Organization: ISC Systems Corporation, Spokane, WA
Lines: 24

In article <2006@lll-lcc.llnl.gov> rzh@lll-lcc.llnl.gov (Roger Hanscom) writes:
>...I'm building a TTL digital counter, and I need a
>1Hz pulse train to feed it.  I'd like to use the 60Hz signal on the
>power transformer, and a MINIMUM of components to condition it and

The power line is a noisy place, and grunge on it will screw up your timing
if it's for anything critical.  Just clipping the raw line is not the best
thing to do.  I saw a design idea in a magazine once that addressed this
problem.  What he did was to design a simple 60 Hz RC-Schmitt trigger
oscillator that was synchronized to the line with a high-value resistor.
The power line only had a limited effect on the oscillator -- high-frequency
junk couldn't sway this oscillator very much.  A rather simple bandpass filter
combined with the output conditioning circuit all in one neat circuit!  
Unfortunately I can no longer find the article, but the circuit itself used 
about a half-dozen components.  

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