Hello dear people of the Arduino forum.
Some time ago I decided that my bookshelf needed some funky RGB LED lights. Not knowing anything about digital electronics I made it an analog project, soldering 25 analog PWM dimmers (based on a 555), each connectiong to 8 LEDs. Unfortunately, a few things went wrong; there was a lot of interference between the channels, and the end result wasn't as funky as I was hoping for. This is what it looks like:
(if picture doesn't show, click here
Now, I did quite a bit of reading on Arduinos etc. and learned a thing or two. Time to redo the project, this time with a micro-controller, and probably some input sensors to control the light patterns. First things first: I should find out how to connect the 25 LED channels to the Arduino so they can be controlled with PWM.
In the Arduino Cookbook I read that using TLC5940's is the way to do this. I figured out how to daisy-chain two of them, giving me 32 channels, which is more than enough.
Each channel consists of 2 parallel strings of 4 LEDS, powered with +15V. Each channel has a current of 40mA. There are 25 channels.This is the set up. Pictures say more than words.
Now, my question is:
-Would it be possible to connect these channels directly to a TLC5940 pin?
*am I correct that the Iref resistor on pin20 should be 1K to allow a 40mA current?
*what is the voltage drop in the TLC5940? Should I adjust the resistor in the LED-chains?
*should I use a transistor (which type, and how to connect?), or an octocoupler (which type, and how to connect?), or are there better options?
My humble apologies for my n00bness, and thank you for your answers!