Fritzing

A circuit to control 2 high power RGB LEDs from an Atmega328 chip via MIDI inputs.

I wanted to create a dynamic coloured lighting system for my band. Something that would be controlable by the band itself. So I designed this board to control 2 high power RGB LEDs (30W each) from a MIDI signal. The LEDs are linked to the board by an ethernet cable (I need 3 pairs of wire and wanted it unplugable), so I made a RJ45 beakout for the LEDs. The circuit is powered by a 36V/3A DC supply. The current flow is controled by 6 LM317 regulators set with 2W 3.6 ohms resistors (gives 350mA) and 6 MOSFETs. LM317 are cooled by small radiators and I put fans on the box to cool the whole board. A pair of LM2596 Step Down Adjustable Converters are used to provide 24V to the red LEDs (which forward current is lower than the blue and green leds, leading to more heat dissipated by the regulators/transistors) and 5 Volts to the controler. They are not represented on the board but their position is noted by holes to screw them on. The MIDI library is used to control the light.

EDIT: important: should you wish to make the same board, an important 220 ohms resistor is missing on the board and mounted directly on the MIDI connector (DIN) to the board. See http://arduino.cc/en/uploads/Tutorial/MIDI_bb.png for details.