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Old December 3rd 04, 09:25 AM
David Maynard
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Daniel J Beardsall wrote:

The problem with an alarm clock is that the chip is
completely contained. The only information coming out would
be seven segment displays - multiplexed. You would have to
convert that back to some usable form OR build a memory device
to store those multiplexed seven segment outputs and then
drive the other displays. Four digits times seven segments
plus AM/PM is 29 D flipflop latches and LED display drivers.



The other displays would be independent of the actual clock, if that's
what you mean. And yes, when I mentioned butchering an alarm clock that
was mostly as a last-resort kind of option.

What type of time do you want to store? For example, if
time of day, then the alarm clock solution is better. AC
powered clocks synchronize with the 60 Hz power line - whose
accuracy is traceable to the National Bureau of Standards. To
avoid the complexity of same, the alarm clock would be a good
foundation to start construction. You would probably have to
beef up or supplement the alarm clock's power supply to power
your latching registers and two additional displays.



The problem there is that I'm not in the US, I'm in the UK, and our
electrical supply isn't quite so simple. It's mostly 50Hz but can
fluctuate wildly, which often interferes with clocks. Besides, I'm not
looking to run it off direct mains, I'm looking to run it off computer
power, so a battery-powered alarm clock was more what I had in mind.

Another alternative is to start from scrap with a single
chip computer. Again, your timing crystal accuracy is just
another consideration. But a single chip computer affords you
great flexibility to enhance your design.



Now you're talking. But I wouldn't know where to start hooking something
like that into something capable of driving LED segment displays. Which
I suppose is ultimately the help I'm after.

Thankyou for your response.

DjBx


I'm still not sure what you're trying to do, precisely, but maybe this will
stimulate some ideas.

http://www.rentron.com/Products/SLED4C.htm