Easy Electronics DIY Projects

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... and better-suited to each of us!

Thursday, March 28, 2013

EASY ACRICH RUSH


What, after all, is in a name, you might think. But for us eager beavers the mere mention of the name Acrich was enough to galvanize us to action! The busy, clogged streets leading to our fav spares shop was covered in double quick time. There below the glass of the "show counter" was the large reel pack with the octagonal beauties. Soon with a few pieces in the pocket and no specs in hand, we sped back to the home lab, itching for some "hands-on" experience!

As many of you are sure to know, 'Acrich' is the trade name of a wide range of "direct AC mains" LEDs manufactured by Seoul Semiconductor, a company mentioned often in these pages for the quality LEDs they make.( http://www.seoulsemicon.com/en/html/main/ ) Naturally "direct AC" means that the bother and
expense (not to speak of the reliability issues!) of a 'buck converter driver' circuit to power the LEDs from the mains voltage is eliminated. Another plus point from the hobbyist's angle is the versatility offered by this device. You can adapt almost any mains lamp to hold the Acrich LED as all it needs is a pair of small screw holes for mounting!


Of course, as we all know, any 'hi-lux' LED needs to have enough heat-sinking, but in the case of most lamp assemblies with large metal plates, this is a non-issue as the mount itself could serve as the heat-sink. In a non-metal lamp assembly, you could choose a small heat-sink to fit and then mount the LED onto that. Just solder the two mains wires to the LED base plate solder pads, and you are done! It is as easy as that!!
 After the mandatory "Googling around", we unearthed some facts about the devices in hand. They were AN 3231 types with a power rating of 4 Watts. The colour was warm white (very good for reading lamps) and luminance flux was around 150 plus, and they were rated at 20 mA at 230 Volts. The octagonal insulated base plate carries the four chip LED in the centre, with a couple of surface-mount resistors and capacitors, and of course, the etched wiring for interconnection. Apparently the four LED dies are internally wired in 2x2, series/parallel manner.
Of course, this apparently was one of the "low horsepower" models from Seoul Semi, as they currently produce some very powerful Acrich-2 models with 'on-chip' integrated drive electronics that probably set the standard when it comes to features and performance.(http://www.seoulsemicon.com/en/html/Product/Product_view.asp?catecode=1002001)

Now the iron was hot and it was time to wire up what we had in hand rather than dream of 'super' Acriches. To go with the 'easy' tone of the project, we chose a left-over 5 Watt LED 'bulb' mount from the previous project. This made it easy to provide enough and more heatsinking, and gave us the option of trying it out in
many lamps and fittings. The assembly, as you can see, is ultra simple and easy. Take care to solder the leads to the base plate before it is mounted to the heatsink, as otherwise a small soldering iron may not be able to melt the solder on account of the heatsinking! The trick here is to wait a few moments while the iron gathers up 'heat inertia', and then quickly do one connection. See that you apply the heat to the pad and the wire and let the solder melt fully to give you a shiny joint. Leave the leads long enough, and then after smearing some heatsink compound onto the back of the Acrich base plate, mount it onto the bulb-shaped heatsink. Be sure to have checked out/drilled the holes for mounting and also for the leads. Feed the leads through and solder them to the bulb base. Screw the assembly together, screw on the diffuser, and yes, you are ready for switch on!

All things considered, this sure is a "newbie" project. The simplicity and the versatility of the Acrich device
and its wiring up lends it to being adapted to many uses. We did try three devices in a "ceiling dome" type of lampshade, and the twelve watts of warm white light was indeed bright and pleasant. A few days of living with the new darling revealed a quirk or two, however! As mentioned earlier, these are simple 'direct AC' assemblies, and unlike the current crop of Acrich-2, these lack sophisticated on-chip drive electronics. This means that when the mains voltage dips during peak hours, the luminance also drops a little. But this is no major drawback, and all in all, the project could be recommended to enthusiastic DIYers wanting to "convert to LED" and go 'green'!!

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Sunday, February 10, 2013

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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