Built 18, LED light boxes for my Church. We wanted a new stage look but the standard forms and LED packages didn't have what we wanted. So custom LEDs were the way to go.
I ordered a bunch of 10W RGB LEDs from china, as a start and began the process of prototyping- design concept, theory, research, testing, cost of materials, first prototype, re-working design, mass construction, and final assembly. All for the unveiling during our Easter Production. The boxes were constructed from pine, painted white on the inside and black on the outside. frosted Plexiglas for the front. Inside each box is a single 10W RGB LED, current limmiter, 3ch DMX decoder and connectors(M/F XLR, 1 barrel)
Couple things I've learned during this project.
1. High wattage LEDs need proper current limiting:
The standard series resistor just isn't going to cut it; Especially in an RGB package, as the voltage for each color is different. So I found this curcuit by Dan Goldwater. It allows for most of the volt-drop/current to be dissipated through a mosfet so you don't have to use giant resisters and is flexible to voltage changes.
"Schematic" Photo: My finished 3ch current limiter boards
2. Heatsink:
Trying to find a cost effective heatsink that will fit in the confined space of my light box is very hard especially if you need 18 of them. I found out that sheet-metal works great as a heatsink. I used a 6"x6" piece and attach the LED via thermal epoxy. It gets hot as expected but not so much that I can't hold it in my hand with ease.
3. Power Supplies and Volt-drop
As a cost saving measure I decided to use only 2 power supplies to power all 18 light boxes. So because of this I had to factor the resistance and distance of the power cables. Some of the boxes were 20ft away form the power supply which is a big problem for low voltage and DC power sources. So always check your wire size and wire resistance; cause over 20ft you could be looking at a few ohms of resistance just in your wire.