On wednesday I've decided to build an ambilight for my flatscreen TV. After a bit of googleing I found the Amblone, but it has only four channels. Then I found BobLight. It is great idea, simple and you can have as many channels as you like. Downloaded the software, installed virtual COM port and watched the data being transmitted. Simple enough. Now the hardware.
At first, this was perfect to try my new LED exposure unit. Google again and looked for schematics. There is a good few of them around, so I took idea here and there and started to design my own.
Schematics were based on the Arduino Nano, The FT232RL gives USB connectivity, Atmega 328P-AU is great foe what I need, as PWM drivers I'm using TLC5940. There is a great library written for the TLC5940 and I have previous experience with that chip. To get enough of current I found logic PNP transistor what can handle up to 500mA of current and has pull-up resistors and base resistor (less parts needed).
Parts came on friday (under €30 for the whole lot + some I needed to restock, like LEDs, resistors)
When I was making the board (first time using photoresist and UV light) I run into a problem. I couldn't get an even coat of the photoresist. Cleaned, degreased, I tried solvent, acetone, acid, nothing. I was a bit desperate, so forums (thank god for them) and found the answer after couple minutes. You have to be in absolute dark when spraying. So half can of photoresist later I got a perfect coating. Exposing itself was easy, etching is a daily bread.