Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!apple!rutgers!cmcl2!rocky8!cucard!ccnysci!sukenick
From: sukenick@ccnysci.UUCP (SYG)
Newsgroups: sci.electronics
Subject: Re: 1Hz signals
Summary: some ideas to get started with
Message-ID: <931@ccnysci.UUCP>
Date: 16 Oct 88 15:08:15 GMT
References: <2006@lll-lcc.llnl.gov>
Reply-To: sukenick@ccnysci.UUCP (SYG)
Organization: City College of New York
Lines: 32

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

How about this:

Take the signal, limit it, schmitt trigger it, then pull it out -

all you need is one chip, a couple of diodes, resistors and a cap.  :

a) resistor series with input;

b) 5.1V zener between signal and ground ( to clamp to ttl levels when +;
   clamp to  -.7v when negative.  resistor a) limits current)

c) This is input to one input of an inverter in a  74..132  Schmitt trigger.
   There are 4 nand gates in the ..132.
   Now you have a relatively clean 60 Hz signal.

d) set up a one shot with the remaining gates with cap/resistors/diode
   (perhaps one diode, two resistors, one or two caps)
   such that it will stay on for 59.5 cycles (when the one shot
   is on, block the input pulses by feeding the output back to
   the second input of the first gate).

   If there is too much jitter in the timing, you may have to
   set the one shot for a shorter time and then add a divider -
   but then  the parts count goes up.

   If the duty cycle is not acceptable, then you can feed the output into
   another gate set up as a one shot.