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Electronics & CircuitsCircuit DesignLED LightingUpcyclingElectronics Repair

LED Desk Lamp Hack

•2 min

Here you can see all the components used in the lamp. It originally used an E14 small-screw 40 W incandescent bulb and has been modified to use eight bright white LEDs.

The desk lamp disassembled on a workbench: the weighted base opened to expose its wiring and transformer, the shade with the LED assembly fitted, the black base cover, and the power cord.

A small transformer board and resistor wired to the lamp's original power cord and switch.

The circuit is pretty simple. I’m using the innards of a 120 V AC-to-6 V DC transformer in series with an 8.2-ohm resistor to power the LEDs. The original 120 V AC power cord and switch are soldered onto the 120 V input of the transformer.

Inside of the white lamp shade, showing eight white LEDs arranged in an X on a round plastic disc, bolted to the end of the gooseneck arm.

Then I made my own LED grid using four pairs of white LEDs in parallel and soldered some long wires to feed down through the tube to the transformer. Finally, I soldered the LEDs and the 8.2-ohm resistor to the 6 V DC output on the transformer.

Close view inside the shade with the LED grid switched on, lighting the white reflector. The finished grey gooseneck desk lamp switched on, casting a warm pool of light across a plywood bench.

I used a water bottle lid to separate the LED grid from the metal arm that used to hold the old bulb. This is to ensure nothing would short out.

The final result is a nice warm white light that is just right for illuminating my desk.

Note

I had all of this stuff lying around, so I thought I’d put it to good use. It really isn’t necessary to use a 10 W, 8.2-ohm resistor.

Update

I’ve since replaced the internal electronics with just a 5 V, 400 mA, 120 V AC transformer with no resistor. While it worked before, it was a little too dim for use at my workbench.

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