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By: Anonymous: doubtingben () on Tuesday, February 05 2008 @ 04:02 AM PST (Read 4012 times)  
Anonymous: doubtingben

Anyone working on turning peggy into a clock?

I understand each led is not addressable with the kit. Any direction on how to go about changing that?

Thanks!
Ben





       
   
By: Windell (offline) on Tuesday, February 05 2008 @ 01:33 PM PST  
Windell

The Peggy kit was not really designed for animation, and in the default way to build the kit, control of the LEDs is only by the row-- it's easy, for example, to blink the top or bottom half of a sign while leaving the other half alone, or to build an OPEN/SHUT sign that has only one half or the other lit up at a time. While I'm sure that it's possible to animate the entire 625 LED display with some simple added driver circuitry to give high brightness and in-system programmability, I haven't yet worked out how to do it, primarily through lack of trying. ( I'll get around to it eventually....) The Peggy *can* be built as a charlieplexed display, trading its very high brightness for the possibility of doing simple animations. (Download instructions for that build here; you will need to add 25 extra 27-ohm resistors and either some wire or wire jumpers.) There are some caveats, however. The method given there does not actually work if all of the LED positions are populated-- the voltage drop on the pins used to program the chip is too high. It might be sufficient of a fix to pull the chip out to a separate board (not actually program it in system). Secondly as a work-around, you could just avoid the particular LED locations that are causing the problem, so it's certainly possible to build a clock, which might be a fun thing to try some time.


Windell H. Oskay
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By: Anonymous: salsa () on Saturday, February 09 2008 @ 06:30 PM PST  
Anonymous: salsa

Still interested in going the charlieplexing route-- it seems like the issue is brightness with lots of LED's, so I wonder-- how is the brightness compared with non-charlieplexed if, say, instead of 90 LED's on all the time, it was charlieplexed with a cycle of three 30-LED images?

Also wonder about a source for 625 2-pin female jumper leads...Smile

-salsa
san francisco





       
   
By: Windell (offline) on Saturday, February 09 2008 @ 08:50 PM PST  
Windell

Well, it seems about 1/3 as bright to the eye, of course. Doesn't look nearly so good, unfortunately. It *could* look very good if you only light up a few LEDs at a time instead and manage the locations that are lit quite efficiently.

Many of the major electronics places have appropriate sockets-- I haven't picked any up yet, but I'll try to do so.


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