Thread: LED Pin Spots

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Dude! Nepboard!
I have no idea how they burned out. Maybe the voltage on the transformer wasn't exactly 'accurate'? I am thinking of a computer power supply with a regulated volatge when I try these again. Something got warm though, about where the resistor was, was warm to the touch and that was through the resin filler and the copper pipe. You think it was my power supply?

Awe, Super Bummer Mike! Man I don't know why the trouble. I would think the power source was the issue. In my opinion a good ol'e computer power supply is the way to go for these projects whether it is lights or wiper motor. I ended up running 22 lights off my hubs and had zero issues.

I guess I could dig a little hole, bury my LED lights, make a foam head stone, and 'resurrect' them next year as Zombie LED Spot Lights!

I just made a couple of pin spots this morning. I got my LED's from Fry's. They seem to work well. Thanks for the tutoral.

Hey, excellent! Glad it helped you!

Great tut! Very simple even a fool like me can follow it!

Yes, this is my favorite of all the spotlight tutorials. Doesn't require odd things like USB cables and hubs that some people may not be able to get cheaply, or guessing voltages on those clip-on LED lights that don't have any kind of specs. At least using a bare LED like this you know exactly what resistor you need for it. I'll be redoing mine with PVC using this method this year.

Originally Posted by MikeBru

Dude! Nepboard!
I have no idea how they burned out. Maybe the voltage on the transformer wasn't exactly 'accurate'? I am thinking of a computer power supply with a regulated volatge when I try these again. Something got warm though, about where the resistor was, was warm to the touch and that was through the resin filler and the copper pipe. You think it was my power supply?

Yep, I'm willing to bet the majority of your problem was your wall wart. Most of them are unregulated, and put out quite a bit more voltage than listed. I've seen 9V WW's put out as much as 12V, and 12V ones put out as much as 18V, and the output changes with the load. I've had good luck with the Motorola and Blackberry 5V wallwarts for old cell phones. The ones I've checked have been regulated supplies, and they're usually 5V 700mA supplies.

Another possible contributing factor is that the LED forward voltage is different for different colors, with red normally being around 2V and blue and green around 3.4 V, iirc. The forward voltage will determine what value your current-limiting resistor should be. That should've been included with the specs for your LED's, though.

One other issue I've encountered with high-power LED's is thermal runaway. Believe it or not, the high-power LED's do generate heat. I had this issue with some LED floods I built. You could sit and watch the current start climbing the longer the LED's were on, until it went past the rating for the LED's. I ended up having to go to a constant-current source to keep the LED's from burning out.

Computer power supplies are great for supplying regulated power. Only downside is they can get rather hot if you don't provide room for airflow for their fans.

Regulated supplies are indeed often expensive. "Switching" supplies are technically more likely to supply constant voltage but not always. However, these two got good reviews. I bought the 5v ones but since I'm very very lazy I didn't get started in time to build my power distribution box, so I'm still using the PC supply I modified last year.

5v 1 amp (1000 mA) power supply with bizarre power connector from All Electronics - $4.50

12v 2 amp (2000 mA) power supply (looks like a laptop adapter) from Parts Express - $7.80