I needed dimmable photography lights for a photo booth project I'm building for a friends wedding. Pre-built lights are quite expensive so I decided to build my own. I based the design on white LED strips which can be purchased quite economically when purchasing directly from Chinese distributors (Like aliexpress.com)
I went with the largest and densest LED strips I could find. The LED strips come in 5 meter lengths; I found for $12 (inlcuding shipping) I could get a 5M LED strip with 600 LEDs. The leds are the 5050 size which is the largest commonly available on LED strips. The 5M of LEDs draw 72W.
Building the Panel:
I build a quick panel out of some white hardboard and pine trim I had around from home renovation work. I sized the panel to fit 10 50cm lengths of LEDs. This made a nice ~60cm x 20cm panel
The strip is directly powered off of a 12V source (I used an old ATX computer power supply). Each segment of the strip was wired to a 18 gauge power supply wire. From here it can be connected directly to 12V or via a control circuit as I have done.
The photo booth I'm building runs on a raspberry pi embedded computer. Attached to the raspberry pi is a PCA8685 I2C PWM driver. Adafruit sells a nice breakout (http://www.adafruit.com/products/815
) board to make wiring it up easy. This way the photobooth control software can simply set the desired PWM duty cycle and be done with it. The PWM output of the PCA8685 is connected to a mosfet which switches the LEDs on and off at the right duty cycle to set the brightness.
Mosfet Dimmer Board:
I designed a simple four channel low-side mosfet switch board for connecting the LEDs (and other DC things) which needed control from the raspberry pi. The hardware design is open source and can be found here: https://github.com/scottjgibson/4ch_mosfet_switch