Michaël Duerinckx


Economic desklamp hack

Today, I decided to fiddle with things a bit.

We had these LED spots in the house, just like these (random google images find), but they broke pretty fast. When I had replaced them with regular halogen spots again, I decided to see what’s inside them, and see if I could perhaps find what’s wrong with them.

It turned out there’s a simple circular PCB with a sort of high-power SMD LEDs mounted on there. In the other part of the spot, there’s a small transformer circuit, which, as it turned out, is what’s broken. I test the LED board separately, and found that it just runs on a typical 12V DC, which is why I decided to do something with them.

I’m not going to bother trying to get the broken circuitry back to work, though.

Anyway, I got the idea to replace the halogen lamp of my desk lamp, with the LED part of the spot. I took some pictures, so you can have a look.

Desklamp 01

Here’s the original, intact lamp.

Desklamp 02

I screwed out the metal fitting for the halogen lamp, and disconnected the wires from the terminals on the bottom of the lamp head.

Desklamp 03

And that’s a look of how it’s currently wired up. The original lamp was a plain halogen lamp, so it just ran on AC. I obviously didn’t want to connect that to LEDs, so I made a rectifier. I firs made a single wave rectifier with a single diode and a capacitor, but the result was a perceivable flicker when the light was on. That diode and capacitor are still left inside the spot, on that note. The diode adds an extra 0.7 V that’s subtracted from the source voltage, which is a good thing, as the mean voltage was slightly too high. Having the Graetz bridge and the extra diode in there, I subtract 2.1 Volts of the source voltage, which warrants a longer lifetime for the LEDs.

Desklamp 04

The spot mounted in there. I think it doesn’t look too bad, even though the head isn’t really enclosed properly. It’s held in place using a screw, as you can see in the last picture.

Desklamp 05

Fired up. This is much brighter than the original halogen lamp, while requiring less power.

Desklamp 06

Another look of the light, and the screw I mentioned. You can see it’s rather bright, as this was taken in rather bright daylight.

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