PC/electronics help needed

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.

Any help at all would be vastly appreciated.

DjBx

Reply to
Daniel J Beardsall
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if you want to power it from the PC use a USB port and interface. Get a USB to DIO board from DLP Design or a USB I/O 24 from

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Tom Woodrow

Daniel J Beardsall wrote:

Reply to
Tom Woodrow

Clock kits are fairly widely available:

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for examples of kits or
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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.

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Rich Webb   Norfolk, VA
Reply to
Rich Webb

Thanks for the help. I already Googled as much as I could before posting this, and everything I found was either not what I was looking for or over my head. The only suitable clock kit I found on the Ramsey site you gave me only has HH:MM, it's essential the clock I make has MMM-DD-YY HH:MM, with the time in 24hr and the 3 month digits as letters. Sorry to be picky. The other site you mentioned, the schematic, I could probably do but again doesn't meet the requirements.

But thankyou still. Back to Google I go...

DjBx

Reply to
Daniel J Beardsall

Have you tried a radio-controlled unit? All the data you want is available, all you have to do it display it. (Maplin used to do them, don't know if they still do). Or buy a ready-made clock and pull the display out.

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rgds
LAurence
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Reply to
Laurence Taylor

Your requirements are so specific that the 'simplest' answer is probably to use a micro (eg PIC). Basically run it from a 32kHz clock crystal and let it do both the timekeeping and display formatting. When the display is off, the consumption is a few uA and a battery backup will do the job. To interface to the PC use a slow serial link (slow because the micro will be slow with only a 32kHz clock!)

For the prettiest display use a set of cascadable self-contained dot-matrix displays (5 x 7 or 8 x 8), which can display anything you want.

It would be nice to run everything from the RS232 port, but I doubt there is enough power to run an LED display, so you will have to plug into the internal power supply.

Dave

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Reply to
Dave Garnett

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