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Author Topic: 32x32 led ghetto matrix :)  (Read 5032 times)
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SE USA
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Just for the sake of "I wanted to" presenting

a 32x32 dot matrix panel!  ;D

this is a shoestring budget,  proof of concept... mostly for code exploration and speed measurements, and again I just wanted to

The current circuit itself is rubbish, starved leds and over driven chips guaranteed for a short life time, so I dont plan on releasing much construction details, but get 2 595, and a 8x8 and multiply

But! it allows me to decide how far down this path I want / need to go, and even if the components are weak it can be beefed up easily, and the current idea is sound and works great

Running a matrix this large (1024 leds) very quickly pushed me out of shiftOut, 64 bits of data are sent to the registers using the ATmega's hardware spi feature

Instead of running the matrix 1 led at a time, were doing 1 line at a time, which reduces on time from 1:1024 to 1:32 (and is overloading each 595 by 20ma, so you can place bets on how long it will last), current requirements are increased everywhere in the display, but clocking in a line of display @ 782khz (with no real cpu load) does open up some interesting ideas, or if nothing else you know if the screen flickers its not the display code!

anyway enough yabber, here is some pictures from tonight, the first time it is displaying bitmap images (made in the gimp)

 


3 wire n power



and of course, I provide a easy to follow wiring diagram
« Last Edit: February 27, 2010, 01:01:18 am by Osgeld » Logged


Phoenix, Arizona USA
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Awesome, Osgeld! What if you stacked a second 595 on each of the current ones (soldering the pins together)? Provided your power supply is beefy enough to handle it, doing so should double the current capacity, right?
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yes, and the idea keeps popping in my head along with I have most of a tube of 595's left, I might as well at least try it
 smiley-wink

power supply is beefy enough, I was aiming for 20ma per row and with the chips eating some voltage up they are running ~10ma per row @ (jeez I forget the exact number) 3.7x volts

 original calculations were at worst case and the whole thing opened up that I am ok but pumping some heat out of that 7805 hence the big heatsink which under a test load kept the whole thing not scalding hot with 9v in and 800ma out
« Last Edit: February 27, 2010, 01:05:44 pm by Osgeld » Logged


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OK went and tried piggybacking, at first just a friction fit test, and yes the difference is great enough to matter

the leds are running at their intended value 15ma, instead of 10, and the entire screen seems more even (not perfect but better) along with the registers sharing current load

worst case and all leds are on at once and stuck, its around 640ma, which is enough to start getting that regulator + heatsink warm with 9v input

so I went back and soldered them, kludge yes, works yes, I know it looks bad on such a thing of beauty ;D and all but ...
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Glad to hear it worked! I am really surprised you didn't smoke that thing first run - it looks so great. Where did you get the panels, if I may ask?

So far I have only found Sparkfun here in the US selling them (everyone else I have checked so far only has 5x7 matrices). I am wondering if there is a cheaper supplier (although Sparkfun's are pretty cheap already).

I am more curious than anything else; its not like I am planning my own panel except in my dreams.

What do plan on doing with it (it would make a nice wall display - maybe go wireless?)...?

 smiley
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got them from ebay; I dont recall exactly where, but TchnclFl found them, maybe he knows, they cost like 12 bucks for 10 with in states shipping by barebones mail

they are cool as tiny 8x8 panels, they have the same dot pitch as a usual size 5x7 which is nice

As far as smoke, well ... the first time I had the entire display on at once was a good smoke test, and I stood by with expectations and a razor saw to cut a bad chip out, but no it took it, for quite a few evenings, no dobut it could take it for quite a while longer, then die, it would have died eventually

Oh also future plans are an entirely different subject for a future date, I have to clean code, optimise and start testing the next layer of ideas and repeat, then I should have a clearer idea

[edit]i have a nes controller, I should slap pong on it at least heh[/edit]
« Last Edit: February 27, 2010, 07:03:14 pm by Osgeld » Logged


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and of course, I provide a easy to follow wiring diagram
Osgeld,
Following your diagram, I successfully toasted all my 595 chips.  smiley-wink
Seriously, though, that's a pretty awesome handbuilt matrix!
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lol and thanks!
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nice build, and the wiring diagram is so easy to follow  ;D

you could put some heatsinks (the fancy ones for your pc memory) on the chips, would help a bit and makes it look even more crazy  smiley-wink
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Cool matrix!

In stead of stacking the 595's you can replace them with some shiftregisterss that can handle the curent like these:

http://pdf1.alldatasheet.com/datasheet-pdf/view/17785/PHILIPS/HEF4794BPN.html

Of course they are more expencive than 595's but you can find them at a little over 1$ a piece, and cheaper in quantities.
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nice build, and the wiring diagram is so easy to follow  Grin

thanks, and isnt it?

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you could put some heatsinks (the fancy ones for your pc memory) on the chips, would help a bit and makes it look even more crazy  Wink

actually they were not heating up at all
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Cool matrix!

thanks!

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In stead of stacking the 595's you can replace them with some shiftregisterss that can handle the curent like these:

lets say this becomes the must have arduino accessory of the decade, then yea I will probally use proper drivers in the design, this was more or less just to play with (and everything is already soldered smiley-wink)
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Very cool!  I was planning on doing something like this on a smaller scale (I don't have enough '595s)! ;D

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TchnclFl found them, maybe he knows

Sure thing.  Here's a link.  They were on sale when I bought them, now they're 16 bucks.  Still not a bad deal smiley.

EDIT:  Actually, those are bicolor.  I don't think they sell just the red anymore..
« Last Edit: February 28, 2010, 01:17:14 pm by Tchnclfl » Logged

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Futurlec has a 8 by 8 matrix with square leds for 1.80 us$

http://futurlec.com/LEDMatrix.shtml
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FCB electronics is a good USA ebay seller.  They have inexpensive items with fast and FREE shipping.  I bought the smaller version of the matrix from them so I can fit more on a breadboard.  I don't have Osgeld's high precision ninja soldering skills. :-)

Scroll down a little bit on this page:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150386988451
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I don't have Osgeld's high precision ninja soldering skills.

actually most of it is wirewrap, everything is soldered to the board, and just the power and ground to the chips are actually soldered into place

but thanks I do try my hardest on ninja soldering smiley

PS: yea those are the same matrices that I am using, but they only have the dual colors in stock as noted above
« Last Edit: February 28, 2010, 06:31:32 pm by Osgeld » Logged


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