PSN-L Email List Message

Subject: 15-minute counter for Placer 400
From: The Lahrs JohnJan@........
Date: Fri, 02 Jul 1999 04:38:58 -0600


Kevin,

That would be great!  I'm not in a big hurry, as I'm dealing with
a herniated disk right now and probably will not get my seismic system
set up again for another month or so.  My plan is to continue using
a one-channel AD (DaTaq) which is fed by coil/magnet/amplifier from
my home-built Lehman.  DaTaq stamps the files with the computer time.
I would like to offset the trace every fifteen minutes for about
10 seconds.  To do this I'll add a summing amplifier after the final
stage of the amplifier.  Once I get the phase of the fifteen-minute 
marks correct, they will be used to derive four clock corrections per hour.

Thinking about it now, it may be tricky getting the fifteen-minute
marks to go off on the minute.  One option would be have a push button
that would set the counter to 899 and block the ticks from the GPS unit 
when it is held down.  The button could be released just before
the 0-, 15-, 30-, or 45-minute mark to set the phase of the ticks.  

Thanks for this offer!  Of course I'll reimburse you for the parts, 
and post the schematic when it's working in case anyone else wants to
try a similar scheme.

John,

How big of a hurry are you in?  What kind of output do you need the
15 minute pulse to be?  What is it going into?

I'll breadboard a circuit and send it to you, but, it will be a couple of
weeks before I can get it into the mail.

KR

>Kevin suggested using a 10 bit counter and some logic
>elements to get a 15 minute pulse.  Can anyone recommend
>a book that would show how to design such a circuit?  Or,
>does anyone have a similar circuit that would only need
>minor modifications?



* John C. and Jan H. Lahr                 *
* JohnJan@........                        *
* 1925 Foothills Road                     *
* Golden, Colorado 80401-1718             *
* (303) 215-9913                          *
* http://lahr.org/john-jan                *
* AOL version of homepage:                *
*  http://lahr.org/john-jan/homepage.html *
* http://giseis.alaska.edu/lahr           *

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Larry Cochrane <cochrane@..............>