EASY CHEAP LED BULBS

Energy conservation is a laudable aim and we are all for it. But when the monthly electricity bills assume the form of a recurring fine, surely our thoughts and efforts accelerate towards achieving some sort of reduction in our energy consumption.

For quite some time we have been "seriously toying" with LEDs and trying to replace as many incandescent bulbs and CFLs with them. Though all the 'ingredients' were available in the hobby market, still our LED lamps remained bulky and somewhat uncouth-looking as compact heat-sinks, drivers etc were not available. Now that situation has been rectified to an extent and let us revisit the LED bulb scenario.

Of late good quality sub-assemblies for LED bulbs have become available in the hobby market at competitive prices. The kit of parts include a bulb-shaped heat-sink assembly, an anodized aluminium LED mounting plate, a diffuser for the LEDs, the switching converter or 'driver' for running the LEDs from the mains, and of course, good quality LEDs at reasonable prices from Seoul Semiconductor. In a previous project we had used Seoul Semi LEDs and now after months of use, we can vouch for their quality and steady light output.

The open market also carries LED bulbs from various known brands, all mostly sourced from China, but coming at a premium price. By going the DIY way, on an average, the hobbyist can save about 30% and have the satisfaction of having built the lamps with her/his own hands using good quality components. The heat-sink assembly is sourced from China, though the drivers are locally made with good quality components. The Seoul Semi LEDs are a bit costlier than their Chinese cousins, but they ARE better and it is best to bet your money on them rather than on some unknown devices. In my case, I was able to garner the parts for a total of about Rs 360 for the 3 Watt version, while the 5 Watt was costlier by about Rs 100 plus. Not  bad deal, all things considered.

Construction couldn't be easier! First off, mount the LEDs (all 1 watt Seoul Semi devices) onto the anodized aluminium mounting disc, observing the correct polarity. The discs are printed with legends, and it is easy even for a novice to follow them. Do apply a thin layer of heat-sink compound on the metal back of the LED before soldering. It is best to tin the pads with a very small quantity of solder beforehand. Clean the soldered disc thoroughly with isopropyl alcohol, as otherwise the residues of flux could lead to corrosion and failure after a year or two. Using three small screws, mount the disc onto the heat-sink, again with a coating of heat-sink compound. Please note that the 3 Watt bulb uses 3 x 1 W devices, while the 5 W has 5 x 1 W LEDs. You may connect up the driver temporarily and briefly touch the +/- leads to the pads on the disc to test that the LEDs light up.

The drivers are constant current switching power supplies and they feed about 300 mA to the LEDs. Mount the appropriate driver into the cavity of the heat-sink after putting in a roll of Kapton or other high temperature plastic sheet (readily available from shops that supply transformer winding wire etc) for insulating the driver from the body.  Feed the red/black wires through the hole in the LED mounting disc and solder them to the + and - pads correctly, again, cleaning up after soldering. Now solder the AC input leads of the driver to the bulb terminals and screw the back firmly onto the heat-sink. Check everything once again and screw on the diffuser. Your LED bulb is ready for service!!

Plug it into a regular lamp holder and you can bask in its cool light confident that your electricity meter is running far slower now! Be a responsible citizen -- save energy, and save some money on the side too!

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