Gas station without pumps

2014 December 28

Desk lamp

Filed under: Uncategorized — gasstationwithoutpumps @ 18:47
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Side view of the desk lamp, showing the pair of pipes tilted down, to keep light from shining in my eyes.

Side view of the desk lamp, showing the pair of pipes tilted down, to keep light from shining in my eyes.

In Summer Project and Summer Project 2, I introduced the project I’ve been working on all summer: a “kit” for making dimmable LED lamps, and I showed the custom desk lamp I made for my son and the table lamp I made for my sister. I’ve finally gotten around to making a desk lamp for myself (I’ve spent most of my “free time” this quarter grading or doing administrative paperwork). The desk lamp is similar in spirit to the one I made for my son, but a bit larger and sturdier.  Instead of using 10-gauge wire to support the LED boards, I used ¼” copper pipe, squeezed flat and drilled where contacts are needed.

I’ve currently populated it with 5 LED boards, but there are holes drilled for 6. I had planned to populate all 6, but I damaged two of the LED boards in assembling the lamp, scraping off a diode from one board, and both a diode and a resistor from the other. Clearly, if I plan to make the LED boards a hobbyist tool, they’ll have to be a bit sturdier. I may need to look into how difficult it would be to pot the component side in an epoxy resin.

Looking at the light from below, you can see the five populated spaces and the one empty one.

Looking at the light from below, you can see the five populated spaces and the one empty one.

Based on the measurements and calculations from the data sheets I did in LED board I-vs-V curve, I should be able to get up to 75 lumens per board, for a maximum output of 375 lumens (450 lumens if fully populated).  The lowest setting on the dimmer should be around 9–10 lumens.

From above, the heat sinks are clearly visible. At the low light setting I expect to use most (around 20 lumens per board), the heat sinks aren't needed, but at full intensity they might get warm.

From above, the heat sinks are clearly visible. At the low light setting I expect to use most (around 20 lumens per board), the heat sinks aren’t needed, but at full intensity they might get warm.

I set them on full for a few minutes and measured the temperature of the heatsinks with an infrared thermometer. This is not a very reliable measurement, since the heatsinks are a tiny target, but I got a peak measurement of around 57°C. At those temperatures, it is clear that the heatsinks are needed, as the case temperature of the MP3030 LEDs is limited to 80°C.

Inside the box is just the dimmer board, a barrel jack, and the nuts for the screws holding the copper pipes to the box.  These cheap wooden craft boxes (intended for découpage) make good project boxes for electronics—they look better than plastic boxes and don't cost any more.

Inside the box is just the dimmer board, a barrel jack, and the nuts for the screws holding the copper pipes to the box. These cheap wooden craft boxes (intended for découpage) make good project boxes for electronics—they look better than plastic boxes and don’t cost any more.

The photos were all taken in my breakfast room, since my desk is far too messy to clear in a reasonable amount of time.

My next lamp project will be a hanging light fixture for the breakfast room. That is somewhat more ambitious project as it means rewiring part of the house—I don’t want to run the 9V DC in the same conduits or junction boxes as the 110V AC. Unfortunately, the junction box in the attic above where I want the dimmer to be is a nexus from which several AC runs fan out. I’ll have to reroute a lot of that wiring to a new junction box, which means pulling some new wires (the wire in the conduits in 65-year-old solid copper with cloth insulation).

1 Comment »

  1. […] stuck an LED strobe light in it (using the same LED boards and controller that I designed for the desk lamps, but with different software in the controller, so that the potentiometer controlled the strobe […]

    Pingback by Tenth weight progress report an Halloween | Gas station without pumps — 2015 November 1 @ 22:21 | Reply


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