We wanted to use less energy and LEDs have come a long way meanwhile. Aim was to replace 6 uplighter 35W halogen lamps. We could not find a suitable design in the stores so decided to build our own living room table lamp. So now we have a DIY 1 m wide 16-LED bar with 1W LEDs resembling candle light (but much brighter) which can be dimmed.
The bar itself was a 20x20 mm aluminium extruded U-profile and hangs from the ceiling using two sewing yarns; the whole weigths about 400 gr.
The driver (updated) works using a potentiometer or voltage-controlled (0-10V) commanding pulse-width modulation while the current remains at 350 mA. Apparently at a frequency of >20 KHz it cannot be heared. The driver does not get warm either so no apparent losses there. The bar can get warm (33 °C in a 20 °C room) as, contrary to popular belief, also LED's dissipate heat. The bar replaces two sets of 3x35W halogen uplighter lamps.
Dimmed to 50%, at a heigth of 1 meter over the table we can comfortably read the newspaper and the bar remains cool. The whole setup cost less than €75. The price of the power supply has come down recently.
The LEDs were "glued" to the profile using heat dissipation paste, put tight with a drop of super-glue and then soldered in a string. In the next project, converting a 50W halogen desk lamp to a 3W LED lamp, I have done away with the paste and used self-adhesive, heat conducting pads instead. Komplett.nl sells article 15342705, which is a similar product (thanks Giel).
seen from the table's perspective |
 dimmed |
 3 LEDs were differently from ordered (middle, edges). |
 easily over-exposed |
 In daylight; the power supply |
 The newspaper (1/8; F2.8; f7.41mm) in LED light. Judge for yourself if you can read it. |
 closeup of the wiring in 2 strings |
 too thick a wiring (to be replaced by a USB cable) |