Re: Digital Clock Circuit Modification Question
From: Zach Zaborny (random_at_nts-technologies.org)
Date: 09/28/04
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Date: Tue, 28 Sep 2004 18:20:24 -0400
Okay, at first I had no idea how to use the mains line for a clock, but this
circuit has helped, it is for a binary output clock:
http://www.hanssummers.com/electronics/clocks/binary/circuitm.htm. One
problem though: his site is not based in USA, but rather in Europe. The
power in hi area oscillates at 50hz, while mine at 60hz. I used his
modification for 60hz and edited his design a bit for it:
http://random.nts-technologies.org/images/Hosted/1hz.jpg. It looks like it
will work. Except, can I use a CMOS 4000 series dual-input AND for the
oscillator instead of the 74LS08? I plan to run mine all on 9V, so it would
be more appropriate.
As for the 12/24 switch, I didn't notice my mistake :). But, will it reset
the hours to "01"? As the AND triggers, it outputs a pulse to the RESET and
CLK pins on the 4510 for 2nd-digit hours, as seen here:
http://nts-technologies.org/random/images/Hosted/clockmod.jpg.
As for it being easier on the PIC; I think that's cheating. I would rather
play with discrete logic circuits and parts than have one microcontroller do
all the work :) I do understand it's ease of use being handy though. Call me
old fashioned.
-Zach
"CFoley1064" <cfoley1064@aol.com> wrote in message
news:20040927044625.21100.00001200@mb-m07.aol.com...
>
> Hi, Zach. I'm not sure what's going on with the second link - it seems to
be
> broken or missing. You're describing the right concept on a 12/24 switch,
> though. If you get together another 3-input AND gate (requiring another
IC,
> I'm afraid) and switch between the AND output on the schematic and the one
> you're proposing, you should be spot on. All you really need are the
three 1s
> - you don't have to add any 0s to the decoding for the alternate reset
signal.
>
> A couple of points. First, using the 555 to generate a 1.000 Hz timing
signal
> is weak. You'll get drift, mostly from changes in capacitance with temp.
If
> you're in for a penny, you're in for a pound. If you're going to go to
all the
> trouble of doing this much counter logic with 4000-series CMOS, add
another
> divide-by-50 or divide-by-60 counter to get 1.000 Hz from your power
supply
> transformer. It may drift slightly from hour to hour, but our friends at
the
> power station are kind enough to bump the power frequency during the night
to
> keep the daily total remarkably steady at 5,184,000 cycles per day (60
Hz).
>
> The second thing is, this circuit has been basically a wire wrap or
perfboard
> wiring exercise for at least a decade. It would be a lot easier with a
PIC.
>
> Good luck
> Chris
>
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