RGB Propeller Display



Summary

This is a color upgrade to my standard Propeller Display project. This version drives 32 red/green/blue (RGB) LEDs, significantly increasing the capability of the display. The TLC5940 can drive its LED output channels at 12 bit resolution (of which I only use 8). Theoretically, the display is capable of full 24 bit color depth per pixel, however I scale that down to 8 bits, resulting in 256 possible colors per pixel. This makes for a spectacular display! Check out some good slow-motion footage of a previous color display I've made at Smarter Every Day, an awesome Youtube Channel that reveals the science behind everyday occurrences.

Powering a Rotating Circuitboard

I talk about the basics of this problem on my standard Propeller Display page. The power requirements for 32 RGB LEDs are even greater, since each "LED" is actually composed of individual red, green, and blue LEDs. Thus, there are a total of 96 LEDs on the circuitboard. If all are turned on simultaneously, the current requirement is 96 LEDs @ 10 mA = almost 1 amp!! To bring that amount of power to the rotating circuit board, I borrow a commutator mechanism from another motor. I remove the plastic enclosure that keeps the commutator brushes stationary, turn it over, and mount it on top of a motor of similar size. The commutator brushes now surround the rotating shaft of the second motor. Then, you can remove the metallic connector that the brushes "commutate" on and slide it over the shaft of the intact motor. Solder a wire onto that connector, and you've completed the circuit from the stationary commutator brushes to the metallic connector on the rotating shaft of the intact motor. You should be able to use the intact motor's casing/shaft as the ground connection, but because that's a flaky connection, lately I've been adding a second commutator mechanism to also transfer the ground connection. See it here:


The PCB

Here are pictures of the top & bottom of the Printed Circuit Board for this project, along with a screenshot of the PCB design.




Wireless Connectivity

I integrated a wireless transceiver, the NRF24L01+, directly onto the PCB. Using a custom NRF24L01+ USB dongle (also my creation), I'm able to upload bitmap images to the display on-the-fly using a custom image loader program on my Ubuntu machine. Here's a pic of the RF dongle:


Schematic