Pixie - 3W Chainable Pixel / outdoor / heat

[zxarr]

Hello folks,

I'm looking to make some outdoor lights. The plan is to encase some form of an LED inside a PVC housing that it sealed with clear epoxy resin on the bottom, with a lid atop that screws on. Initially I was just going to make dimmable white LEDs, but the Pixie has got me wondering if I could use them for some multi-colour fun!

The issue I see is the heat. I can easily tone back the brightness with a little bit of coding, but I'd like some opinions from those that have used them. If they're sealed in a water tight PVC construct, will the Pixie 3W Chainable Smart LED Pixel be alright?

If not, is there something similar I can use with a reasonable amount of light output?


Thanks!

[adafruit_support_mike]

You will have to deal with heat. About 70% of the power that goes through an LED gets converted to heat, which is fairly good compared to the 95% that gets converted to heat in an incandescent lamp. That still means each Pixie will act like a 2W heater, and you can expect similar heat from any other LED running at the same power.

Not only will that be a problem for your enclosure, heat damages LEDs. Any misplaced atom in the semiconductor crystal (called a 'lattice defect') makes it harder for electrons to flow through the crystal. Current flowing through an LED pushes on the atoms anyway (it's sometimes called 'the electron wind'), and heat makes it easier for the electrons to push atoms out of position, creating lattice defects.

Lattice defects increase the resistance through the LED, so current flowing through the LED generates more heat, making it even easier to produce more lattice defects. Eventually, the process gets out of control and the LED burns out.

High-power LEDs like the Pixie come on aluminum heatsinks to slow down the process as much as possible. The heatsink needs to be able to dump energy somewhere though, so your enclosure will need some kind of cooling system.

The cooling system doesn't have to be active, with fans or anything. It can be another, larger heatsink with exposure to the air outside the enclosure. You'll probably want it to be made out of metal because metals conduct heat well, and copper or aluminum are among the best heat-conducting metals.

[zxarr]

Almost a year later... Wow. I realized I never had this set to notify me and other things took priority, but now that I've ordered all the tools to do another project (soldering station, breadboards, etc), this one has come back.

Sorry, do the 3W pixie LEDs come with heat sinks? If so, I can easily make something to include a larger heat sink. Well, not easily, but I'll make due.

[adafruit_support_mike]

The Pixies don't have built-in heat sinks, but they do have thermal protection. If the microcontroller sees the temperature rise too far, it will shut off the LEDs and let things cool down.

You can test the LEDs to see if they do shut down when operating the way you want them to. If they do, the first line of prevention would be a fan to keep fresh air moving through the enclosure. You can use a standard PC fan with a heatsink to get as much cooling as possible from the incoming air.