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Topic: (not another) LED Matrix project (Read 6 times) previous topic - next topic

Francis Shanahan

Kicking off soldering tonight on an RGB matrix project. Here's the schematic. Will post back when done.



Now THAT is what I would like to try.  There are a lot of projects that are using these Maxim parts that are ridiculously expensive; I don't want to spend over $10 each cathode for R G B matrices.  You're using four 74HC595 packages, which are (in DIP form) about $0.60 each.

The layout of your schematic is a bit odd, but it looks like you're shifting in the bits for each row of cathodes in parallel.  Then you are using one more shift package to drive one anode at a time.

No support for dimming the board, as far as I can tell, but if you can tune the right resistors, it should look great.

Going to do more than one matrix?

Francis Shanahan

Some decent progress made tonight, should easily finish tomorrow assuming I haven't screwed something up.

To answer your questions though:

Let me preface with : I'm a complete noob, this is my 2nd project and am learning as I go.

I'm using an RGB 8x8 common anode matrix from LedSee (only $10 on ebay). I agree I think the matrices available out there are way overpriced at $35++ and then you have another $30 for the driver boards. And what's the point? For me I wouldn't have learned much from using those.

I've already roughed this up in a prototype which you can see here:

I was able to get fading implemented using some code from this guy:

Basically I'm building the same project as him only he knew what he was doing. It's fun though and I'm learning a lot.

The reason for the layout is to try to squeeze everything underneath a single matrix (6cm X 6cm). One of the shift registers will be on the outside but no biggie. As will the arduino.

Here's a snap of the PWM working in mockup.

more tomorrow probably.




well done!

being told that 'I knew what I was doing' doesn't happen too often  :D
be sure to post more of it when it is up and running.



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My projects: RGB LED matrix, RGB LED ring, various ATtiny gadgets...
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If you want to implement PWM brightness control for the entire display at once, you can connect the /OE pins not to ground but to an I/O pin on the Arduino.  If you choose one of the PWM pins, just remember that it's /OE, that is, it's enabled when the pin is LOW and the analogWrite() function will work backwards (0 = full bright, 255=off).

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