Thursday, June 28, 2012

LED display

As if I needed another project, recently a couple of my friends moved into their first apartment, and I told them I would build something cool to go in the living room. I decided that a music reactive LED light bar would be an awesome idea, and started thinking about the best way to build it. I settled on using a strand of "RGB pixels" from a Chinese seller that use the ws2801 controller. They are basically a strand of small modules that each have a controller and three RGB LEDs, and are all chained together. They use a two wire SPI-like serial interface to allow 24 bit color control for each module. I am going to mount 20 of them into a enclosure with some diffuser on top to make a kind of bargraph display, and control them with a ATMEGA328 microcontroller. In order for the device to be music reactive, I decided a microphone would be easiest, since that way it doesn't need to be wired to the speaker system. Originally I was just going to use an envelope detector circuit to get sound level information, but I decided that to make for more interesting music animations an MSGEQ7 graphic equalizer chip would be best. The datasheet for this chip says that it has 20dB of amplification built in, but that means I still needed an additional 20dB or so to make the microphone signal usable with this chip. I used a rail-to-rail op-amp to accomplish this. The controller now is all built, but I have not yet programmed it and I am still waiting on the led string. I'll update when I have made more progress!

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