# How to use RGB LED spots with Medusa DMX and VSA



## Hooked_on_Scares (Apr 16, 2009)

Hi all,

Here's a video tutorial I made for assembling, hooking up, and animating an RGB LED spotlight using the Medusa DMX and VSA. The LED spotlight is based on a PCB I designed, and made publicly available at batchpcb. It's designed to support (3) 1-Watt 10mm LEDs you can purchase on TopBright LED on eBay. If you decide to make one of these, be sure to size the resistor appropriately (both for resistance value, and power dissipation).

The first video describes how to assemble the spotlight, given the PCB, LEDs, and resistors. Then, the second video shows how to set up an animation sequence using the newly-built spotlight, a Medusa DMX prop controller, and VSA for the animation software.

Enjoy!
- Hook


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## RLDP (Jul 4, 2011)

Very nice tutorial! Is there any reason you went with the 10mm LEDs vs a star based led? Any cooling or heatsinks necessary for these?


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## Hooked_on_Scares (Apr 16, 2009)

Hey, thanks RLDP! Regarding the 10mm vs. star based... The idea with the spotlight design was to minimize cost, make it easy to assemble, and as small as practical. There's a few ways to design these better, but all cost more, or make the design larger. The trade off in this design is ultimate brightness, and possibly longevity (TBD).

Background for others: LEDs run cool (compared to light bulbs), but they do generate heat. If you let them get too hot, it will shorten their lifespan. There are some surface-mount LEDs out there (as opposed to pin through hole), that have a metal slug behind the LED. This mounts directly to a heatsink that's often in the shape of a star. Like this one. These integrated star units can shine brighter, for longer, because they keep the LED cooler.

However... using (3) of these (to make an RGB light) would make the spotlight large, and as far as I've seen, these are usually 140 degree dispersion - they'd require a separate lens for spot use. The first problem could be solved by using an RGB version (3 chips in one package), but those don't converge the colors properly (in the units I've seen, anyway). Also, if you were to buy the emitters separately, and mount them to a custom PCB (like the one I designed, for example), these would be more challenging to solder, without damaging the LED (since they have the metal heatsink slug *beneath* the LED).

Given the potential problems with overheating, I did what I could on the PCB to alleviate this. There are large copper pours on both sides of the board, to act as heatsinks. They're coupled together by the led mounting hole, as well as four vias. Also, there's extra exposed copper area on the top of the PCB to solder the wider LED lead directly to the copper pour. In addition, I'm going to suggest that people run these LEDs not at the 300mA they're rated for, but between 100-150mA. That's what you see in the video.

- Hook


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## buckaneerdude (Sep 12, 2008)

The size of the spot at that distance is just what I need for our rising coffin corpse guy.


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## Hooked_on_Scares (Apr 16, 2009)

Additional info on temperature control in this post.


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