Light fixture building: components, ideas?

Flashlight Modding and DIY Parts
1

So for my next Halloween project I got several 3W 365nm LEDs from Epistar, pre-mounted on star PCBs, as well as these heatsinks:

Screenshot 2023-05-28 at 09-58-54 TO-220 koel profiel 20°C_W - 5 stuks - Opencircuit

and some 41.5x2mm ZWB2 filters.

I plan on running the LEDs at 350mA instead of their rated 700mA to help keep them cool. Even at 350mA the LED already gets hot to the touch after a minute or two, although not boiling hot. I don’t have any equipment to measure the temperature unfortunately but I don’t think it gets excessively hot with this current.

I’ve come to realize that I will need some sort of fixture to mount the LED/heatsink combo and the filters. It will have to be tiltable. The base of the fixture should have a magnet for easy attachment to the metal doorframe. Swivel is not required since I can just rotate the entire magnetically attached fixture.

Of course if I replaced the Epistar LEDs, which have quite a bit of stray visible light to them, with Nichia LEDs I would not need the filters so that would make the fixture a bit easier to produce.

  • What would be a good source for Nicha UV LEDs, pre-mounted on a star PCB?

  • Are there any readily available off-the-shelf components that would make it easier to build a fixture like this and where can I get them?

  • Since the LED is already getting somewhat hot I guess the fixture will have to be a fairly open affair as as not to block the flow of air.

I could design and build something from scratch out of stock sheet metal, threaded stock and some 3d printed parts (to hold the filter) but that will be quite a bit of work. I’m hoping there are some components to make this easier.

Any suggestions?

2

You say the LED at 350ma gets hot to touch, is this mounted on the heatsink?

There are a bunch of flexible neck “machine LED light” if you search on AliExpress, I’ve no idea the quality of these but might work for you for the housing. I spotted them originally as I wanted to make a nice smallish high CRI desk lamp, but never went through with ordering.

3

Yes, that was when mounted on the heatsink. Lighting the LED with just the star PCB as a heatsink (heatspreader really) for longer than a few seconds might not be the greatest idea.

Of course I’m feeling the temperature of the silicone dome, not of the LED junction itself so that will be hotter. If I had to guess the temperature of the dome is 50-70 degrees Celsius / 122-158 Fahrenheit. It’s a bit warmer than I had expected at that current and with this heatsink.

In truth the LEDs don’t have to last that long. They will be on for a few hours each hour on Halloween so even with a reduced lifetime of just a few hundred hours they will probably serve me for two decades at least. I just don’t want them to burn up in less than 100 hours or so.

There’s a thermally conductive pad between the LEDs start PCB and the heatsink to aid in thermal coupling. Maybe liquid paste would give better results.

Thanks for the machine led light suggestion. Might be difficult to find something that will fit my components exactly though. Maybe I should just 3d print the entire thing instead of mixing 3d printer parts with stock metal parts.