I’m still getting the initial build documented, but you can now see a bunch of pictures I’ve taken of my first Propaganda-made PC board in action. It’s a 4x4 RGB LED shield that sits on top of an Arduino (or Seeeduino!). The LEDs are controlled by a trio of TI TLC5940 LED driver chips with each one controlling one of the color channels. This allows for some very bright applications; the TLC chip supports 4096 different PWM levels per output channel, and they’re driving all 16 LEDs at once with no multiplexing.
The project is documented at combee.net/rgbshield. I’m going to put up assembly instructions and a full parts list soon.
You can see the picture set online at unwiredben.livejournal.com/290964.html. I’ve got a few tweaks to make for a 1.2 version – I’d like to use a dual-row of headers on the signal pins to allow using default signal routing with a set of jumpers, and I want to add the circuit to the BLANK line to keep the LEDs turned off during reset and board programming.
whoa thats pretty cool. It seems you could probably adapt that pcb fairly easily to account for the presold led matrix that seeed and so many are selling these days.
I don’t know much about those chips but can you drive each led individually? as in, make designs or alternate colors between different leds?
The TLC chips in this sheld are driving all 16 LEDs all of the time. There’s no multiplexing, and the Arduino board only has to write new values to the Arduino when it wants the display changed. Scaling it up to a 8x8 matrix would be possible, but annoying. You can use two TLC5940’s to drive the 24 pins for the 8 columns, but they you’d need to reload the TLC for each row. That might refresh too slowly. You could use 4 TLCs and drive two rows at a time; that might be a better multiplexing solution.
