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Topic: (not another) LED Matrix project (Read 16051 times) previous topic - next topic


Jan 31, 2009, 06:06 pm Last Edit: Jan 31, 2009, 06:22 pm by halley Reason: 1
I have a little question : what is the wiggly line inside the board edge ?

It's to guide the attachment of the matrix to the board.  The only way to identify pin 1 from pin 17 is to notice the key grooves on the matrix part.    The actual matrix outline in yellow is showing the key grooves; the white wiggly line is for the silkscreen to help show this relationship.

In addition, if someone wants to use several boards+display side to side, maybe we should add a row of headers, with the DIM / SCK / SCI / VCC / GND shared with the already existing 6 pins header going to the arduino, and taking the SERIAL OUT of the 4th 74HC595 and wiring it to the SER pin of the "outgoing" header".

I was also thinking the same thing, but I wasn't sure of the best approach.  Ideally, a ribbon cable with identical wiring to all boards would be nice, but I think you're right, two headers, one for input, one for output, may be required.

I don't think one Arduino could manage all the data required for two matrices, anyway.  The generic 6-pin header is to go to any interested hardware, whether it's an ATmega168 or something larger.

However, I'm trying to make the empty space in the middle large enough I can optionally attach an Arduino Pro Mini to it.  It would fit between the matrix board and the matrix itself, listen to commands in some way, and manage the refreshes.  Any ideas there would be welcome.

Unfortunately, a Mini Pro + Matrix Board will probably be the same cost (or worse) than the existing Matrix Backpack at Sparkfun.


Don't know if you saw my current project that I called matriduino.

What I want to do is attach an ATmega168 on the bottom side of a PCB, and an 8x8 LED Matrix on the top side. I have a few more chips with it (TLC5940, ULN...) to control the thing.

Maybe we could do the same with this baby : just have a 7805, ATmega168, XTAL and Stuff, program it via ICSP and have a connector for I2C / Serial communication. This way, the board + matrix can be standalone or controlled via a master chip using the I2C connection.

The matriduino is bit more complex, as I want to have PWM control over each leds, "high power" via 12V supply for the leds, etc... but the idea is the same.

But this can be expensive and not worth trying to do, as Sparkfun already have done it...


Yup, watched your matriduino threads, but as you say, it's a lot more complicated.  And when you're done, you still just have 8x8 lights.  Gotta see how we can economize to support those big red/blue light towers in your website photo.




I like where this is going!

Having worked with the MAX72xx and RG matrices for about a year now I'd really like to see a low cost RGB "backplane" with PWM.

I'm sure you will get a lot of suggestions, so I might as well express two thoughts.  ;)

- I like the idea of being to expand horizontally - add more matrices - but I also like the idea of being able to expand vertically - i.e. "sandwich". Bringing the I2C, SPI, and COMM out of the bottom of the board as discrete connectors has served me well. It's made it easy to add RTC, EEPROM, RS232, IR, etc.

- When you finalize the design, perhaps it might be a good candidate for Seedstudio's propaganda service. They could also supply a compatible matrix.

All the best with this project.


"Data is not information, information is not knowledge, knowledge is not understanding, understanding is not wisdom."
~ Clifford Stoll


Nota bene : I used resistor networks in a QSOP package, but those don't really come cheap.
R220 = 2.35$ : http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=VSSR16-220-JI-ND
R330 = 1.89$ : http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=VSSR16-330-JI-ND
It might be interesting to use 0603 resistors instead, to cut the price down.

Well, I got around to looking at the datasheets for these little QOIC resistors, and also sampled some of those 0603 types.  I already have a PCB on the way, so I will use the QOIC for that one, but the 0603 types are way way way cheaper (can't buy less than ten, and it's still cheaper).  For whatever reason, 330ohms was 2/3 the price of 220ohm in the QOIC also.


keep us posted as you receive the PCB ^^


Feb 19, 2009, 04:20 pm Last Edit: Feb 19, 2009, 11:18 pm by halley Reason: 1
Yet another update.  I'm still waiting for my rev01 board (based on melka's original) to be delivered, but I finished routing my rev03 board ideas already.

The rev03 has:

* ten pin connection
* only five pins required (GND, VCC, SCL, SCK, SERIN)
* another five pins optional (SEROUT, GND, DIMR, DIMG, DIMB)
* solder jumpers to connect DIMR, DIMG, DIMB to GND if not desired
* one 0603 pad for capacitor

It may be required to have more capacitors to deal with major current switching, but I'll wait until I have the rev01 board in-hand to evaluate the situation on an oscilloscope.  It may be a non-issue for one matrix.

This is part of what BatchPCB.com shows you when your design passes all the tests for isolation and trace sizes:

I'm also starting to think about how I can drive two 8x8 RGB matrices using three TLS5940 packages.  Each package has 16 PWM outputs, so you either use 1.5 of the packages on one matrix, or three packages on two matrices.


WOW this is so awesome. I hadn't checked back at this thread for a while and am amazed at all the great work. I had thought to make a PCB but my Eagle skills are non-existent so I'm very grateful that folks have taken the time to do this. Looks excellent.

I had a small update on my end; I completed an enclosure for the device. I've uploaded some pics here:


The enclosure is cherry, lexan and 4 flat head stainless steel bolts to dress it up.

Again, for whatever reason I can't figure out how to get some decent pics of it.

Some Video:

Also had a video up on YouTube of my daughter playing with it.

What's great about this is the kids. They love it and it's a great learning tool. My youngest uses it to learn colors (red + blue = purple) and my daughter uses it to learn letters.

Overall this is was a great little project. Again, really excited to see where you guys take it.

Keep us posted.






Feb 24, 2009, 05:14 am Last Edit: Feb 24, 2009, 05:16 am by halley Reason: 1
Argh, well, it was good practice (my first SMD soldering job).  I did okay with the soldering, and did get some lights to light up, but there are some circuit issues in my rev01 board that won't be easy to fix up in code or with a razorblade.  (Some traces I would need to cut and re-route are underneath the SMD parts.)

The good news is that I think my next rev will be ready to run with the existing sketches found on madworm's original blog ("My 2µF"):  http://blog.spitzenpfeil.org/wordpress/2008/09/21/8x8-rgb-matrix-first-prototype-on-perfboard/

Just have to wait for it to arrive.  >sigh<


Feb 24, 2009, 10:16 am Last Edit: Feb 24, 2009, 10:16 am by sosox Reason: 1
I have just got this LED matrix today, that's what  I would like to learn later.
But I have not it's spec so that I even don't know the definition of all the pins...
Would u like to show me some  information  about the LED matrix ~
thx~ ;)


As with any part, google for the word datasheet and whatever part number you find stamped on it.

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