Greetings!
I'm new about this, and I want to control a 8x8 led matrix (bicoloured). But, I have a doubt, I don't know if I can use these 3 IC's. I will use the TLC5940 for PWM, because I can do a lot of colors. The 74HC595 for control the anodes, and the UDN2981A for power it. I attach a simply schema of that I have in mind.
Thanks!
PD: Sorry for my bad english 
Hi,
Yes I believe that should work. You may have a problem if you are using a 5V supply and blue or white leds, because the voltage drop accross the UDN combined with the voltage drop across the '5940 may not leave sufficient voltage for those leds. Red and green would be ok I think, as they need around 1V less than blue or white.
Paul
Thanks you Paul!
I only will use a Red and a Green Leds, is for made an Midi controller, so, the lights will power up one momentally. There are the light that I will use
http://www.ebay.com/itm/371020432510?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
I saw this too:
https://plus.google.com/photos/106630138154329739101/albums/5287314028583882001?banner=pwa
He doesn't use any chip for drive the leds, and he has 4X 74HC595 with PWM
Hi. But those are RGB leds. Do you intend to use only the red and green colours? If so, that is a waste in my opinion. In the future you wish you could make more colours, like in your second link. Also there will be a problem. The green leds in RGB leds need a high voltage, compared to other green leds. You may have the problem I mentioned before with insufficient voltage if you are powering with 5V.
Your second link is also to an RGB led matrix. I think the colours are mixed using pwm, performed by the Arduino (not using its pwm pins).
I would recommend to you a much easier way. Get or make an 8x8 matrix consisting of ws2812B leds. These are easy to use. No driver chips are needed and many colours can be mixed.
I will only do 4 colors (Red, Yellow, Amber, Green) not more. I buyed the RGB Leds yet... There aren't a solution for this? if I cant do any, I will only put 3 colors(R,G, RG) in my project... I saw these matrix (2nd link) and the specs are the same (2,4V~ Forward Voltage for Red, 3,4~ for Green and 20mA of current). If I need more voltage, I can put an Ac adapter, is another option, but, if I can, I prefer not do it (because I will use the project with a laptop, and it can be uncomfortable
Greetings, thanks you!
If you were going to use a pre-assembled matrix, it would be quite different, but if you are going to assemble the matrix yourself, it is much, much more sensible to use MAX7219s.
In particular, the MAX7219 performs all the multiplexing for you. This is a huge simplification of your program, not to be overlooked lightly, as well as your board wiring.
For multicolour LEDs, to use MAX7219s, you divide the 8 by 8 matrix into two 8 by 4 (for 2 colours, or four 8 by 2 for 3 colours where you "lose" a couple of pins on each device but gain a little in multiplex time) as you construct it.
If you are going to use a pre-assembled matrix, you are better off getting one with the corresponding driver board - "colorduino" if I recall correctly.
@Paul__B: Using max7219 will not allow the OP to mix yellow and amber, as requested.
@IviDrowPool: check out these links:
Thanks to everybody!
I know that I cant use the max7219. I'm thinking that those leds are too expensive, its only for make 3-4 indicators. What is the problem? The current? We will put row resistors for limit the current in the leds, I dont need a lot of brightness. Or using mosfets or another kind of transistors for drive the leds. I'm still thinking that my leds have the same properties that all led matrix that I saw (I can be mistaken) I saw that video
I doesnt pretend to drive the leds all day, is momentally and I didn't need a lot of brightness :S. There aren't any solution for this?
If you are making your own matrix, you can use max7219, as explained above.
Which leds are too expensive?
Why do you need only 3 or 4 indicators? You began by asking about a matrix!
In summary, your last post was very confusing!
The video does not explain things very well. I have seen it before. He talks about a "common anode" matrix, but all matrices are both common anode and common cathode, so it is meaningless. He should say "row anode" or "column anode".
PaulRB:
@Paul__B: Using max7219 will not allow the OP to mix yellow and amber, as requested.
Well, yellow is of course, not a problem but yes, I missed the reference to wanting PWM for other colour variations.
Well, that pretty much lets out the TLC5940 too, because while it does PWM, getting it to multiplex as well is going to be a world of pain!
Looks like the Adafruit NeoPixel module is the answer then (cheaper than the UK one, otherwise pretty much identical).
Addendum:
PaulRB:
Why do you need only 3 or 4 indicators? You began by asking about a matrix!
True. 
PaulRB:
The video does not explain things very well. I have seen it before. He talks about a "common anode" matrix, but all matrices are both common anode and common cathode, so it is meaningless. He should say "row anode" or "column anode".
Since it is a bi-colour matrix, it is in fact either common anode or common cathode. Whether that is row or column then depends on the mounting orientation.
Make something like this is my idea, adding items that I will use that arent incluyed in the original
My english is so bad, and I cant say exactly the things that I think
Wow! I have no idea what was going on in that video, but it all looked very cool. I did only see 3 colours illuminating tbe buttons. But I think there were 81 buttons in total, not 64. I still think ws2812b leds are the way to go. It will be a complex project, so keep each part as simple as you can. The ws2812b leds may seem expensive compared to normal rgb leds, but when you add up the cost of driver chips, and the time you spend making the hardware and software work correctly, I think they are easily worth it.
Hi! I think other idea. I can use Blue color instead Yellow color. The colors aren't very important for me. The only think that I will have 3 colors for indications (Red for Recording, Yellow (Blue) for show an audio clip and Green for show what is playing in this moment) Can I use Max7219 or my principal idea? I won't mix any colors if I use this.
EDIT: For the other 16 leds, I can do other 4x4 Matrix, no?
If you do not want the PWM, then what I have suggested using MAX7219s will undoubtedly be the simplest; you do not have to worry about multiplexing at all. Yellow is simply red plus green and generally the colour mix of both at equal brightness (the MAX7219 permits brightness selection of the matrix as a whole) gives a satisfactory colour.
Since you are "sharing" the MAX7219 between the red and green parts of the LEDs, you use one MAX7219 for each group of 32 LEDs, so if you need 16 LEDs more, that is simply another MAX7219 chained (using the same 3 control pins). you need to have all the MAX7219s set to use the same multiple number however, even if only partially used.
I think that the best option is use Max7219 and don't mix the colors. Paul__B, can you explain me that you did for use the 3 colors and the 80 buttons? I will use Only Red, Green and Blue, there are a problem using 3 Max7219 and connecting each color? (8x8 red, 8x8 green, 8x8 blue, and the common anodes)
Thanks to everybody!
