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Using AC with LEDs (Part 4) - The New Technologies

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Some of the roadblocks in general acceptance of LED in the home has been the relative high cost per lumen and the complicated and clumsy power conversion systems.

In recent months, a number of new developments promises to bring us a step closer to a LED-powered world.

Taking its cue from the ATX system which powers our computers, a new line of "Green-mode" adapters will convert any voltage from 100v to 240v, AC or DC, to run combinations of 1- or 3-watt LEDs in numbers from 1 to 7. These modules are under 1" in length and can actually be inserted inside the base of a household light-bulb.

Here, I've chosen a conversion module designed to power a single 3-watt LED at about 700mA, but have attached it to 8 x 100-milliAmp "Superflux" LEDs in parallel, which allows me to simplify heat-sinking and light dispersion.

The entire assembly can fit on a board 1.5" on each side.




 
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Step 1:

The module can be obtained here for about US $3.00 in single quantities, shipping included.

The 3-watt design means that there is no voltage over 5-volts on any of the LEDs, and they are completely isolated from the mains.

The large "MHX" capacitor seen in the images is used to filter the input, so its wire leads do carry high voltage. Cover them with electrical tape to be safe.

The "Green-mode" design rectifies and smooths out the mains voltage and uses it to drive an oscillator at about 100KHz. This square-wave is applied to a small flyback transformer which converts it to a much lower voltage . The currents in and out and the temperature are measured 100000 times a second and the oscillator is turned off until proper operation is restored.

Step 2: The LEDs

Picture of The LEDs
LED 100mA-2.jpg
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The LEDs I'm using here are 100mA (so called 0.5-watt) "Superflux" or "Piranha" LEDs. You can get them here.

They are able to handle this power without over-heating because cooling fins are built-in under every module.

The close-up shows sets of gold wires which go through the phosphor into 3 over-sized LED devices. Under low power, the separate diodes can be seen.
jenov5 months ago
Hi qs can I know if I am using 3x3W LED driver constant current at 600mA. How many superflux LED do I need and how to layout them. Thanks.
qs (author)  jenov5 months ago
Usually, for 3*3W units, you need to have 30-35 parallel strings of 3 or 4 20mA white LEDs in series, or about 120 pieces. For red and amber, you will need even more, 6 in series. Note that all LED strings must be identical and preferably from the same manufacturer/batch.

To be safe, use the specified output voltage range and divide it by 3.3v (use 2.2v for IR, red, yellow and orange). Round it up to get the minimum number of LEDs to connect in SERIES. Then take the output current and divide it by the operating current through each LED. It is advisable to use 15mA for multiple LED setups like this, and to maximize the higher efficiencies of the LEDs at this current.

Note that with 120 LEDs, you can direct drive off mains. For 110v, just connect 2 rows of 60 in opposing polarities. For 220-240v, a simple bridge using four 1N4002 will drive an entire chain of 120.
nolte9195 years ago
Is there a reason you went with 8 LEDs instead of 6 or 7 seeing as the output from the driver is 650 - 700 mA?
qs (author)  nolte9195 years ago
Better esthetics? :)

Seriously, the lumen/watt output of LEDs go down the harder you drive them - a complete reversal to what we've learned with incandescent bulbs.

So, not only would 8 LEDs allow me to run things a bit cooler, it actually produces a tiny bit more light than 7 LEDs would!
stp715a qs2 years ago
I want to drive 80 x 100-milliAmp "Superflux" LEDs in parallel. Do you know if DX has a driver for that? Also, any suggestions on all parallel or series-parallel is appreciated.
Thanks
qs (author)  stp715a2 years ago
If you are particular as to the exact number of LEDs, a far simpler (and efficient way is to hook 50 to 65 of them in series and put them on a rectified AC source. If you are on 220-240v AC, then you can direct drive 100 to 120 of them. See my previous 'ible here: http://www.instructables.com/id/Using_AC_with_LEDs_Part_3_The_BIG_light/
arirang7775 years ago
WHOAAAA!! So the amount of light between the 8x100mlA and the 1X700mlA is practically the same? of course as you pointed out, eight LEDs have better heat dissipation and light dispersion than just one. Will these particular LEDs used in your project fade after some usage? As long as you match the rate of 700mlA of this converter, you could use any LED type (red. green, etc) in its given quantities, right? I HAVE SEEN THE LIGHT!! :-)
qs (author)  arirang7775 years ago
No - in parallel circuits you cannot mix your LEDs. Each LED has to share an almost exact percentage of the total, and, if the Vf of one is substantially lower than the others, it will 'hog' all the current and basically self-destruct.
arirang777 qs5 years ago
Alright, I won't do that. Let me see if I understand the basic then: in this project's case, you used 8 matching LEDs to fulfill the converter output. Why 8? because that's the needed number according to their own power requirements to fully cover the 700 mlA of the converter. Now, if I get other color LEDs, green, red, amber, superbright white, etc, their own power requirements changes, but if I use ONE type of color only (all red, all green, all amber, etc) using your formula I will get a number of LEDS to fully cover the 700 mlA of the converter. I guess I should have made clearer my question by adding that as long as I fully cover the output (mlA) of the converter, I could use any number of the SAME LEDs on the array safely. Not different LEDs within the same array, but different color arrays instead. (thanks for the warning, though ;-] ) What could be your considerations in the following case: -Let's say you want to place the converter in the middle of a room, but you want to place the LEDs around the corners of such room. Distance between converter-LED will increase of course, therefore its internal resistance. You will have to consider the length/diameter of LED wires, but where this r (ohm) value fits within your formula? Thank you, qs, for your explanations and this instructable. I fave'd it. Cheers!!
qs (author)  arirang7775 years ago
Yes, as long as the 8 (or 9!) LEDs share the same electrical requirements, and add up to 700mA, or MORE, then you should be fine.

The advantage of splitting up 700mA into smaller 80mA lights is that the current loss is 100 times less (Ploss = i*i*R), so thinner wires may be possible. Probably #26AWG wire if the distance between lights is under 10-ft.
stp715a qs2 years ago
Nice instructable. Thanks.

When you say "add up to 700mA, or MORE" does that mean greater than 9 superflux LEDs? Can 20 superflux LEDs be used on the single controller?

Thanks

qs (author)  stp715a2 years ago
In essence, since the device is Current-limited and the LEDs are connected in parallel, you can have any number of LEDs which can handle at least 700mA. With 9 LEDs, the current going through each will be about 78mA. Although this doesn't sound like much, remember that for LEDs, light output per amp goes up as the current goes down. In other words, light production is more efficient if we drive it with a lower current.
stp715a qs2 years ago
Thanks for the response.

Do you think I could use your AC design connecting (4) of these in parallel?
http://www.bigclive.com/happy.htm

Thanks
No - the two are not compatible! The design you indicated is meant for a constant voltage source, like from a fixed output wall-wart. It uses resistors to burn up power which will otherwise over-drive the LEDs.
arirang777 qs5 years ago
Supercool! QS FOR PRESIDENT! (after Obama, of course.) Thanks again and keep the great work man!
qs (author)  arirang7775 years ago
As far as the light output goes, more sources tend to give more even illumination - like the different between a 'naked' bulb and a frosted one. There will be a slow reduction in light output - the 10- or 100,000 hour life is based on the point at which light output is exactly half of when it is new. Most of this is caused by heat, so make sure everything runs cool and you'll get the service you expect from LEDs.
adi19772 years ago
Hello My Friend

It was a great pleasure seeing you work. Dear Friend as i'm not a professional in electronics I want some help from you please can you design me a simple drawing for making about 5 to 10 watt Powerful led tube for 220V power supply so that i can fully light up the room.

Also Please tell me the details of the parts and their specifications. I'll be very thankful to you.

(if i apply 1, 3 , 5, 10, 20, 30, 50 Watt LED's) what shall be the drawing.

Thanking You
Adit Pal
qs (author)  adi19772 years ago
If you haven't already, take a look at this Instructable Once you know the Voltage and Current requirement of your LEDs, you can use the links provided to obtain the proper 'driver' for your lights.
mcarrell2 years ago
I recently converted nearly my entire household over to LEDs of various configurations and from various makers including Phillips, Feit, and others..

I have found there are many tricks to choosing the correct light. Certain manufacturers and certain bulbs tend to make more "spot light" while others are very good at diffusing light and are ideal for more "flood" or general lighting requirements.

The great thing about these bulbs is generally speaking, most of them are dimmer compatible which relieves us of the problem of most CFLs not being compatible with dimmers.

One of the fairly unknown things in general is that these lights are better for the health of you and your property! They are at large flicker-free unlike CFLs so they don't tend to give people headaches or inflict irritability. They put out a more stable linear spectrum of light which is closer to sunlight than fluorescent light could ever be. The part that's also great for your property is that they don't emit xrays or plastic-yellowing UV spectrum unlike CFLs. AND THEY CONTAIN NO MERCURY!!! :)

Now having recently acquired bulbs for as lot as $10 each, I am confident once people find out how superior these bulbs have become, they will soon start flying off the shelves when they reach the ever-sweet $5 mark. I also believe that 2012 will be the year the LED lighting revolution really kicks into high-gear.
Congratulations on making that switch. I've worked in the LED lighting business for several years, and they are indeed superior to CFLs in some ways, and still getting better.

However, a couple of the claims you're making regarding CFLs over LEDs are simply untrue. We're all familiar with the older, flickering fluorescent light tubes as the bulb or ballast nears the end of its life. These used magnetic ballasts that fired 120 times per second. However, all electronic ballasts and ALL CFLs use high-frequency power supplies that fire the bulb thousands of times per second, far faster than any human can perceive as "flicker". Furthermore, MANY LED fixtures ALSO fire the LEDs some thousands of times per second, so any flicker effects from one would be similar in the solid state LED model.

You also claim a more stable spectrum of light from white LEDs. This is also false. Both types of light start by generating short wavelength light (UV or deep blue), which is then converted by phosphorescent material into longer wavelengths. Phosphor technology is well-established, and what you're essentially claiming is that the exact same phosphors somehow create a better looking or more natural looking light when a different excitation source is used. Neither one is all that close to sunlight - all phosphor base lights are much weaker in the red end of the spectrum, and all "warm white" phosphors are less efficient than the "cool" ones and have shorter useful lifetimes, and this is also equally true for both CFLs and LEDs.
unni.0p3 years ago
I HAVE ONE 3 W LED SENT ME A DIAGRAM AC LIGHT
dilisi3 years ago
Great Instructable!
popcanguy3 years ago
excellent instructable, simple yet useful.  Thanks for the great work :)
I've ordered the parts and will try building it.  Instead of the 0.5W superflux, I've ordered these 0.5W strawhats.  They have the same angle as the superflux (120-140 degree), but a bit bigger at 8mm. Price is a bit more if you buy bulk on ebay, 62 cents for the cool white strawhat compare to the 59 cents for the cool white superflux.  But the best thing about the stawhat is the brightness.... cool white superflux produce about 55k mcd while the stawhat give 110k mcd, and for the same current too! May need bigger pcb, but we'll see :)
caboteria4 years ago
More experience: I built a module with 2 drivers and 2 rows of 8 lvehk leds in sockets (i.e. two independent arrays, each driven by one driver). I put it in an enclosed fixture and it worked for a while but it got hot enough in the summer so the LED's all burned out. It looks as if with 8 of the superflux LED's per driver you need some airflow to cool the LED's or they'll overheat, at least if you live in a warm climate. I'm going to try again but this time I'll let the module hang from the fixture instead of being enclosed in the fixture's glass globe. I think I might try it with a few more than 8 LED's per driver also to reduce the current through each LED.
buckaroo1694 years ago
Awesome, a multitude of thanks for the link to the driver module. To many builders just know they "got it from somewhere' but do not give source.
Again, MANY THANKS. Check out http://www.amazon.com/Flex-Strip-White-Ribbon-Meter/dp/B002DIZVBA/ref=sr_1_105?ie=UTF8&s=home-garden&qid=1247960685&sr=1-105 for a good source of SMD LED Ribbon
caboteria4 years ago
I've made a few of these now and they work great! About the only thing that can go wrong, which is unfortunately really easy to do, is to damage the LED's by putting too much heat into them when you assemble the bulb. They'll work for a while but then start to flicker and eventually burn out, and once a few burn out then the others get much more current so they tend to go, too. I'd strongly recommend that anyone who's unsure of their soldering skills (or are sure that they have no soldering skills, like me ;) use soldertail sockets and then plug the LED's into the sockets. It's a little more expensive up front but at least for me much cheaper long-term. An easy way to tell if this happened (at least with the LVEHK led's) is if the led's are slightly different color - some more yellow, some more blue. They should all be exactly the same but color changes seem to be a good leading indicator of heat damage that will cause them to fail prematurely. The only trick to using the sockets is that a typical DIP socket is wider than the LVEHK led's but if you space the sockets with one empty protoboard row between them then you can plug each led so that it's making a bridge between two sockets.
qs (author)  caboteria4 years ago
Very useful information! Thanks caboteria! When using sockets do not use the rounded 'machined' types - they are too narrow for the pins of the LEDs. The regular spring loaded ones are fine.
turbonut484 years ago
I've been looking for this type of info for a long time. Your explanations are really good. I've got the parts on order and can't wait to build something. Probably start out with a small nightlight for an extremely dark hallway at night.
qs (author)  turbonut484 years ago
I'm sure you will have lots of fun doing it! Good luck, and keep us posted!
sumatra4 years ago
I built this using the same LED driver but different LEDs (more below). The driver put out a very constant 632 ma no matter how many LEDs I used. I was expecting more, maybe 800 ma. I'm curious to know if others found the same result.

I wanted a warm white light so I used these LEDs. Not only is the light still "glare-y", the color is a sickly pale yellow-green. I'd stay away from those LEDs.

Finally, regarding the eye's sensitivity to color, our eye's are most sensitive to green. For example, see this Wikipedia article.

I look forward to trying this again with better LEDs.
qs (author)  sumatra4 years ago
I've used these LEDs before (see this 'ible and my website) - they're not bad for making tiny flashlights but their light dispersion is not suited to area lighting - the spot is small but irregular. And, as you discovered, the 'fringing' causes ugly color haloes.
sumatra qs4 years ago
Have you used any warm white LEDs that you found to give a pleasing light, not harsh and with the proper incandescent-like color? Thanks.
qs (author)  sumatra4 years ago
I wouldn't call the incan's output 'proper', although you can try amber LEDs to approximate it. Personally, I have no problem with the output of white LEDs, as long as they have an even dispersement and no hotspots.
mrmarshall14 years ago
doyou know of a power supply lke the one you used that would be able to power two of these http://www.seoulsemicon.com/en/product/prd/zpowerLEDp7.asp
leds?
qs (author)  mrmarshall14 years ago
It's not cheap, but this 5W driver should fill your need - it can power 1 to 6 SSC devices.
mrmarshall14 years ago
sorry about the missing letters my keyboard is faulty.
Confused about the photos here in step 4, the description in both composite photos is the same so they contradict each other. I assume the bluish side is the LED's, and am looking for warm-light LED solutions and variable color-temperature solutions with mixing/dimming. Got suggestions? Thanks!
For natural light you could use equal parts Red Green and Blue leds, although the lumens per watt will suffer slightly.
qs (author)  volto4 years ago
It's kinda ironic: the human eye is most sensitive in the blue spectrum, we 'see' it more, and that translates to glare. And since lumen measurement is based on the range and sensitivity of our vision, doesn't that mean that, by definition, only low lumen-per-watt lights can feel warm?
qs (author)  blazingpencilsdotcom4 years ago
The 'blue' half is indeed the LED output, although its spectrum is almost identical to outdoor noonday light.

As volto said, white light can be approximated by a mix of red, blue and green, but that solution is limited because the yellow is produced by adding a bit of green to red and doesn't really remove the 'glare-y' feel,

Another approach is to use a 'warm' white LED, which has more yellow phosphor. Although somewhat warmer feeling it's also less efficient.
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