My LED Worklight Project

I started a thread a little while ago about calculating junction temperatures for an array of LEDs, and I thought that I'd post up the nearly completed project that spawned the question:

The project started while I was at work wiring a new house one day (I'm an Electrician). The house didn't have an electrical service to it yet, so the site was being run off of a generator. At this time of year it stays dark late into the morning, and gets dark again early in the evening. The added load of floodlights to the usual drills and saws and whatnot was taxing the generator, tripping the breakers often. I decided to turn my $5.00 500W floodlight into a very expensive but much more efficient light. (Going from 5A to 0.5A on the 120V side)

This is the result:









I used 30 Luxeon Rebels pre mounted to 10mm square boards, 5650k running 135lm each @ 350mA for a total of 4050lm. I used a Philips Xitanium 40W 1750mA driver to power them. They are all mounted to a 13cm x 7cm 1.4ºC/W heatsink. The center LEDs have a 50º optic attached to them. I had optics for all of the boards, however there was not enough flood with them all attached. I've also got a 105ºC thermal switch wired in series with the LEDs and attached to the heatsink as a safety, as this was a wee bit expensive.

All I've got left to do is figure out a clean way to seal off the face of the heatsink from the bowl of the light, because I don't want moisture and dust coating the LEDs from the ventilation holes I had to drill into it.

I'll post comparison pictures against another 500W flood I have once it gets dark tonight.

Sorry the pictures are sideways, I'm having trouble getting them to stay rotated.

mobiusrx7 said:

All I've got left to do is figure out a clean way to seal off the face of the heatsink from the bowl of the light, because I don't want moisture and dust coating the LEDs from the ventilation holes I had to drill into it.

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You may get better results covering those holes with material from an air filter and adding a fan. This is the solution industrial computers use; high-efficiency air filtration with air blowers.

If you don't want to worry about all that, then just about anything clever and gooey should work. I have had good luck with plastic partitions and 5-minute epoxy; think of cutting up a 2L soda bottle at worst.

AnAppleSnail said:

You may get better results covering those holes with material from an air filter and adding a fan. This is the solution industrial computers use; high-efficiency air filtration with air blowers.

If you don't want to worry about all that, then just about anything clever and gooey should work. I have had good luck with plastic partitions and 5-minute epoxy; think of cutting up a 2L soda bottle at worst.

Click to expand...

I'm not sure about the filer idea, the holes are not really accessible, and the filter media would need to be able to be changed easily. Sealing shouldn't be too bad, I'm thinking some sheet metal partitions as backing, and then using a high temp cauking/silicone to fill the entire gap. I am also considering a fan as extra cooling, however incorporating the power supply and fan in a way that it won't get damaged without making the whole thing look really awkward (vain, I know) is escaping me at the moment.

Output:

So the output is substantially less than the Halogen (considering it is 5-6000 lumens less output), but it is still plenty bright enough for my purposes. And obviously this isn't a perfect test, but it is close enough. I'll use it as is (once it is sealed) and maybe revisit the idea when I'm done some other projects.

I would suggest if doing this again to simply "glue" a couple of big Bridgelux parts to the back of the spotlight enclosure which is aluminum and use the case of the light as the heat sink. Much cheaper and more effective heat sinking.

Semiman

I've always wanted to do something like this. One suggestion if you need more flood move the whole LED plate forward so the optics rest on or close to the glass window. and you could use the space behind for a fan and/or more heat sinking mass

This was the thread I was trying to find.. I was thinking about doing the same to my flood light since the bulb blew and hard to find a replacement. But curious how the heatsink is mounted.. did you have to drill or anything like that?

SemiMan said:

I would suggest if doing this again to simply "glue" a couple of big Bridgelux parts to the back of the spotlight enclosure which is aluminum and use the case of the light as the heat sink. Much cheaper and more effective heat sinking.

Semiman

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I don't think the case alone would suffice as a heat sink by itself, not for this amount of heat.

I've always wanted to do something like this. One suggestion if you need more flood move the whole LED plate forward so the optics rest on or close to the glass window. and you could use the space behind for a fan and/or more heat sinking mass

Click to expand...

That is a good idea.

This was the thread I was trying to find.. I was thinking about doing the same to my flood light since the bulb blew and hard to find a replacement. But curious how the heatsink is mounted.. did you have to drill or anything like that?​

Click to expand...

It is great to see thread like this. thanks for mobiusrx7 .

Nice build. Those rebels have a ton more headroom so you could always double the power input and go with active cooling if you need it brighter.