27 LED desk shelf light with variable voltage controller
Feb 17 2012 by FaTe
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I said in my last project (see link above) that now my floating shelf was in place the last step would be lighting in some way. As I don't want a desk lamp taking up space or something big and clumpy hanging I decided to make my own (again).

For this lighting set-up I'm using 27 daylight LED bulbs which is more than enough on a single USB lead. All the LED bulbs are in parallel meaning they are not joined in a big row but each powered individually.

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First job was to bond the plastic to the balsa-wood backing, the balsa provides a work surface while soldering so the plastic doesn't melt or deform, also wood dissipates wood better than plastic. I used UHU 300 Epoxy smeared across the sheet and then just using books and other heavy objects to bond them while it dried. All the electronics sit on the top so it needs some space when against the bottom of the shelf. I added 2 ply wood beams each 1CM * 1CM * 38CM super glued and then a little Epoxy I had left over. In total there are 27 LEDS, 3 rows of 9. Each LED is 4CM apart to give maximum spread and keeps a good bright focus with no dull spots in the middle, also I'm using also using a resistor per LED (BLUE|BROWN|GOLD).

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Good planning is key so I properly marked out the area on the back and drilled the LED holes for the legs to pass through. That was 57 holes to be drilled lol. Now each LED is mounted in place with its capacitor I used heat-shrink pipe to insulate the bottom of the LED and by pulling the LED up as I heated the piping it pinned the LED in place so no glue Now because everything is powered from 1 USB lead I simply connected every LED negative pin leg to a rail and shared them all back to 1 point. To stop contact shorts I used black electrical tape over all the legs leaving only the positive pin legs out. Next I soldered 2 LED positive legs together in pairs on each row, then created connections between each pair to lead back to 1 point for the entire row. Once all the rows are soldered it was simply a case of running of just 2 cables to connect all 3 rows up.

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I missed taking a picture but I installed a variable voltage control knob which simply adjusts the voltage allowed to pass through it by adjusting the knob (like a light dimmer switch). This goes between the LED positive connection side and the black switch you can see. So I can now adjust the brightness of the LED rows and of course turn it on and off. I can see when I'm soldering now!!!

A very simple but time consuming project this one, the result however is totally worth it. My dark corner is no more and I can properly use this space again.
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