Re: PC/electronics help needed

From: Rich Webb (bbew.ar_at_mapson.nozirev.ten)
Date: 12/03/04 

Date: Fri, 03 Dec 2004 01:25:11 GMT

On Thu, 02 Dec 2004 18:25:57 +0000, Daniel J Beardsall
<beardsall@ukfsn.org> wrote:

>Greetings all.
>
>Assume for a moment that I have no knowledge of electronics (not true,
>but I only know what I've picked up and that's rather patchy). I'm
>looking to make a little addon for my PC and I need a little help. I'm
>after making 3 time/date displays using 7-segment (numbers) and
>10-segment (letters) LED displays. One of them should actually show the
>correct time, the others I'd like to show other static times, preferably
>with the option to change them occasionally. The latter parts should be
>within my reach but the actual clock is a bit more of a problem, our
>school was a bit crap and didn't actually teach us how to do that.
>
>I'd rather make it from scratch but I'll butcher an alarm clock if I
>have to.
>
>The other thing is that it needs to be powered from the PC's power
>supply, so it'll need to run on either 5V or 12V, with some form of
>battery backup to power just the real clock when the machine is switched
>off. If somehow it could be made to display the system's internal time
>that would be wonderful, but not necessary.

Clock kits are fairly widely available: www.ramseyelectronics.com for
examples of kits or www.hanssummers.com/electronics/clocks/matrix/ for a
schematic. Google for "LED clock schematic" or similar.

It's such a wide open question, though, that there are many, many
possible solutions.

Maxim has quite a few clock chips that support battery backup. You'll
need to interface them to the display, somehow. A microcontroller is one
way to do that, as is discrete logic or a gate array.

www.maxim-ic.com/products/timers/real_time_clocks.cfm 

-- 
Rich Webb   Norfolk, VA

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