Number of LEDs?

Hello! I have a quick question for everyone. I am wondering how many LEDs and Arduino board can individually control. When I say individually control, I mean the color and brightness of the LED.

Long story short, I am interested in making a similar project that I found on YouTube. I can't post the URL as this is my first post, but if you search "64 LED table wave", it is the first result or check my next post. :slight_smile:

Can someone give a new guy some tips and pointers of where to start? Thanks!

Here is the YouTube video link:

Thanks again!

I am wondering how many LEDs and Arduino board can individually control

"Control" is a very broad term.
It could mean "turning on or off", or it could mean "setting the brightness of".
Google "charlieplexing".

Can you tell me more about the 12 TLC5940 that he used for the table? What they are and what they do exactly?

http://www.arduino.cc/playground/Learning/TLC5940

"The TLC5940 is a 16 channel PWM unit", does this mean that each of the TLC5940 can control 16 LEDs?

(Sorry for all the noobie questions. :()

yep, basicly on chips like these you plug your led's into + and let the chip control the - which lets you individually address each LED and its brightness via pwm

(and we like noobie questions, they are easy lol)

I am assuming there is some limit to the number of TLC5940 chips you can use? I read that they are daisy chain-able though.

TLC5940 is really good and probably easiest way, however they are very expensive. I personally like to use 74hc595 chips and multiplexing, they are cheaper and you can control allot of leds, In one project I control six 8x8 red/green led matrixs at 4bit color depth whit only one atmega168 and 13 595 chips, that's a total of 768 leds. However there will not be much cpu time left for other processing.

/Jon

74hc595's are made for logic level signaling, at a usuall absolute max of 20ma on each output you wont be driving leds very bright, depends on your application

If you just want led's to light, or if you want to be able to see them in daylight, for example

as far as chaining them, I am not sure what the max would be, I am pretty sure its a lot

I am not looking to power an amazing number of LEDs. Maybe 128 or so, and being able to see them during the day is important. I want them to be bright! :slight_smile:

128 led's as in 128 led packages with 2 or 3 color led's inside (which would be 256-384 in reality)?

Shoot, I didn't think about it that way, hehe. I wanted to use either 64 or 128 of the RGB LEDs.

This is getting complicated, hehe.

yea it will, but it will clear up

next questions

  1. are these individual led's or packaged as a matrix
  2. common anode or cathode
  3. do you want to have 3 colors, or do you want to mix them
    3b) if your going to mix them how many possible colors

next questions

  1. are these individual led's or packaged as a matrix
  2. common anode or cathode
  3. do you want to have 3 colors, or do you want to mix them
    3b) if your going to mix them how many possible colors

Good questions. I am just starting to learn about this stuff, so maybe you can help me with some of this, but here were my initial thoughts:

  1. I was thinking individual RGB LEDs. I was thinking something like http://www.sparkfun.com/commerce/product_info.php?products_id=105 Can I mix the colors with these LEDs to make, orange for example?

  2. Good question? I don't know enough yet. Could you help me with this one?

  3. I want to mix them so I create colors. So, I could do something like mix red and blue to get purple.

3b) Again, I'm not sure? Wouldn't that be up to the LED?

Thanks for all your help! I really appreciate it!

  1. yea you can mix those, problem is, most conveniently packaged driver IC's including the ones on page one control the cathode (connect and disconnect to ground) , and those led's linked are common cathode (all 3 led's in the package has ground are tied to 1 wire), to go that route you would need common anode ( one + leading to 3 independently controlled grounds)

  2. If your going to make your own solution from scratch, it doesnt matter... BUT if you want to use a driver IC almost all are setup to flip on and off the cathodes, and not the anodes, so you would need a common anode led in most situations

  3. super you just multiplied the complexity

3b) no it would be up to what you have driving the led's, for example...

looking around recently showed some maxium surface mount chips that could drive 2 arrays of 64 leds, and provided 4 levels of "brightness" so 6 of these jokers (at 8 bucks a peice, + smt board development) could run a 128x128 rgb array with upto 64 unique colors by themselves (4 ^3) the same could be achieved by 3 of the TLC5940 per bank of 16 rgb led's, depends on resources and scale I guess, with enough of both you could drive a 16.7 million color HD jumbo-tron if you wanted (in low draw resolution)

on the flip side, if you had a beefy power supply and a clever way to hook it up, you could make a 3'x3' "mood" table

Just to add another dimension into the mix.
You can multiplex the TLC5940, I have done this on a four times basis. That is expanded the capability from 16 LEDs per chip to 64. That means using 3 chips you can have 64 RGB LEDs.
http://www.thebox.myzen.co.uk/Hardware/Mini_Monome.html

Am I misunderstanding how RGB LEDs work? I thought that if you were to illuminate the red portion as well as the blue portion it would "create" a new color, in this case purple. If you were to mix the various colors and brightnesses, you would produce many different colors. Am I wrong?

How else would the table produce that rainbowing effect? Here is the link again since it is on the first page: 64 RGB-LED color wave table (Arduino, 12x TLC5940) - YouTube

no your right, but how much your able to mix them is a function of what your using to drive them, and not necessarily the led

If you were just to turn on red and blue, you would get purple, but maxing out at about 6 unique colors

if your able to half turn on red and fully turn on blue now you have a new shade of purple, but increased complexity in order to drive the red led (or whatever one) at 50%

Its a choice for you to make how many colors you want to have, and how much wiring your willing to put up with