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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