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Miscellaneous LED topics on other pages include:
I have done many projects using LED's. The biggest and best is the World's Brightest Bike Light in 2010. Head there if you want to see the big stuff first.
100 W LED 2009
To paraphrase Crocodile Dundee: "That's not an LED, THIS is an LED!"
Lighting a lighthouse! This is a hugely powerful LED made from a 100 x 1W LEDs. It cost AUD$500 from China (in 2009) on an eBay store here. It produces 7000 lumens and runs on 34 V 3.2 A. It needs to have a heatsink capable of perhaps 90W. The Bunbury lighthouse is on but you cant see it's beams easily in the photo from this angle. The 100W LED runs on three 1.3 AH, 12 V SLA batteries attached to the LED which is resting on on the wooden fence here. It is fan cooled and runs around 3 A 34 V via a 0.4 ohm resistor, if I recall.
If you look closely, you can see the bonding wires for each row of 10 LEDs. So lets turn it on and increase the power slowly.
This is a series showing increasing current from 0.1 uA, 1 uA, 1 mA, 100 mA in turn. Voltages range from 16.36 V up to 27.61 V. The first pic is a long exposure of 19 seconds and the last pic is covered by dark glass from welding goggles and is 1/160th sec.
Note the uneven lighting of the different LEDs on the left at 10 mA. I was particularly worried about the row where the rest of the LEDs are brighter suggesting the dead segment is a short circuit. At a higher current of 100 mA, however, all segments lit equally. I was worried for a while.
Above shows a small CPU heatsink bolted to the back of the LED. Last photo shows my infrared thermometer after a short run with the small heatsink. It is rated at up to 80 C operating.
Specifications:
Above shows a comparison with a standard candle at 10 mA, 100 mA, 1000 mA and 2,700 mA. Painfully bright and swamps the candle for photographic reference.
The left photo above shows my shed lit with the LED plus a 150 W incandescent globe for comparison. The right photo shows it held up to the sun. These LEDs are designed for street lighting. Many US cities including LA and NY are doing feasibility studies on replacing their 100,000 plus streetlights. These would replace low or high pressure sodium lights or metal halides. Low pressure sodium is unpleasant because of the monochromatic yellow but very efficient. High pressure sodium is more white but less efficient. Some comparative information on luminous efficacy is here. LEDs are about as efficient but have lower maintenance. There are other advantages in smaller packaging and better beam direction to reduce wastage. For example there are different beams for a street than an intersection or junction. All this does stack the data in favour of the LED. Cost being the main difference. A range of streetlights is here up to arrays of 200 W. Different colors up to 500W here with 20,000 lumens. And cheaper 100W LEDs at $118 here.
I built it up into PVC tubing (above) with a rectangular connection that just nicely fitted the heatsink/fan. I used a CPU fan of medium size as the last one was nowhere near good enough. This one seems to keep the temp down to perhaps 42 C. I was making the black housing to accommodate 3 SLA 12 batteries. Then I thought it might look interesting as a mechanical arm attachment vaguely reminiscent of Iron man or one of the Transformers (robots). You can see how bright it is in sunlight on my arm. I was rushing to finish this portable full power version by Earth Hour so I could turn off the lights (briefly) while I had a group of photographers here during a Tesla session.
The left photo above is the LED on the left in comparison with a 500 W halogen floodlight on the right. Beam coverage is similar or better and it looks brighter to me particularly when you look at the shadows. LED is running on the battery pack at perhaps 75 W. The right photo shows the LED in comparison with car headlights on high beam (100 W halogens each). Beams are very different but LED is easily brighter.
Above is the LED shining through a 180mm camera lens which projects a very clear image onto the corrugated shed wall. You can see great detail with the 30 times magnification including the bonding wires and chip details. One can even pick out the light from a single segment with an additional lens like this "crystal ball".
Above is the LED on the left It so happens that the chip light is in a "3" shape brought out with contrast adjustment. One of the individual LEDs is marginally brighter or in better focus and stands out unusually.
Above is the LED with a focusing lens. I have played with a lot of random lenses, spherical mirrors, Fresnel lenses and glass spheres out of my optics box but have no idea what I am doing. The best performance was with a magnifier used for looking at skin lesions and I have bolted this to the LED. It is close and broad enough to capture a reasonable proportion of the light output as given by the light output curves.
Above is the LED on my bike with the focusing lens. It makes my very adequate 3 W LED bike headlight look rather puny. It's like having a new weapon on your space fighter. Now, let's go and use it irresponsibly...
Above, left, is the normal 3 W LED on my bike with the lights of a passing car just as it is about to pass me. Then the same with the 100 W LED. Now, how about burning some stuff?
Well, I tried the obvious (above) - black cloth on the unfocussed output.
Here are the results in a sequence from switch on to 14 secs later. So there
it is. It can burn things.
How about burning a CD case above? Took 1:45 mins to make a hole, but my heatsink fan was also cooling the target a bit. I had to give my batteries a bit of a hand to keep up near rated power as I still don't have a proper constant current supply.
To test the infrared output, I used a special infrared filter (specs here). By connecting it to my silicon photodetector cell in the center photo, I got 9 mV of infrared only output. On the right photo without the filter I get 425 mV which is total output. Hence the infrared is only 0.5 % of total output. Similar readings on an incandescent globe give about 92 % infrared. What this means is that the incandescent globe puts out much more total radiation but most of it is in the infrared. The globe radiates the heat whereas the LED puts it into a fan cooled heatsink. The 100W LED article has done reasonably well in the media. It got 100,000 hits after it was slashdotted and made it to 80 websites. These are shown on the Backwards links page - search with (control F) for 100W LED. Was popular on cycling, LED and scuba forums.
LED light patterns
2008
Above left photo This is a small commercial battery powered LED array that my wife wanted suspended above the BBQ. I have covered one of the LEDs with blue cellophane. The right photo shows it suspended above the camera. Now just give the lights a push and take a time exposure.
Above left photo Pushing the array in a simple circular motion with some spin gives intricate geometric patterns. Center photo It's like you could almost grab it. This looks very much like a toroid used on top of my Tesla coils. The right photo shows the path followed by the one blue colored LED. This next one below is a little fan with programmed LEDs in one of the soft plastic blades and was bought in Hong Kong (thanks Gail). The flash rate and sequence of each LED varies.
Above left photo The fans with its 5 LEDs is stationary. The right photo shows it running and you can see the pattern which constantly changes.
Left and center photos show the fan rotating spiral giving a lot of detailed patterns. Pushing the array in a simple circular motion with some spin gives intricate geometric patterns. It's like you could almost grab it. This looks very much like a toroid used on top of my Tesla coils. The right photo? Hmm.. only a mother could love a nerd like this.
Green ring 2002 (below) uses a 6 volt miniature battery, microswitch and a 120 ohm dropping resistor. The green super high intensity Gallium Indium Nitride LED is rated at 14,000 mcd at 20 mA (= 5 mW) and is dazzling in line with its 15 degree beam. They cost A$10. The microswitch is operated by a thumb press.
Three high intensity LEDs (red 8,000 mcd, blue 3,000 mcd, green 14,000 mcd) are flashed at different frequencies although the little battery doesn't handle the full rated power of the LEDs. It uses 3 x 555 IC's, 3 capacitors, 6 resistors, a microswitch and the battery.
This was a bit of silliness as a one off for a "sock hop' dance to give my toe tapping some visual impact. The red Aluminium Gallium Indium Phosphide LED is rated at 8,000 mcd and is visible through a light pair of socks. It is flashed with a microswitch as your foot hits the ground.
This model was made in about 1981. I think you have to be drunk or stoned to get much pleasure out of these and as I don't do either, they are only brought out on special occasions. It is interesting watching them circulate though a disco from person to person. I haven't lost them yet. They use a 555 timer driving a 4017 CMOS decade LED driver with each leg driving 4 standard low intensity LEDs (?20 mcd) with each side rotating in opposite directions and cycling through different colours. There is a speed control to go from standstill to continuously on. It takes a lot of interconnections around the frames. If I was to remake them I would use a smaller rechargeable battery and high intensity LEDs. The coloured rings are, of course, the appropriate fashion accessory for the glasses.
Well, just occasionally I wear them in 2008, 27 years later like at night in this 24 hour charity relay walk. I have resisted the temptation to put in high intensity multicolor modern LEDs but maybe I'll make a new model sometime.
1 W white LED 2004. This LED (Luxeon Star) is 180,000 mcd and draws 1 watt (350 mA at 3.4 V) and was claimed to be the worlds brightest series of LEDs in 2003. Since then 5 W LEDs are available (and of course, now that it 2011, the 100 W LED at the top of this page). It has a heat sink and a separate collimator for a 10 degree beam. It cost AUD$36 on eBay. Shown below after I mounted it on some acrylic with a voltage regulator in the handle. The brightness comparison with a pencil torch is dramatic and is over 10 times brighter than the LEDs above. It came with its specifications on a floppy disk.
This is an electronic art piece made in the early 1980's inspired by a sound only version in a local art gallery. This has a variety of circuits to flash the 50 or so LEDs in various ways. There are 3 mercury switches to sense the position of the pyramid which can be tipped with any of the 3 apices up with different results. It turns on in response to decreasing ambient light intensity hence will turn on as you approach. The actual light intensity controls the flash rate. It 'plays' electronic sounds and also has a door bell chime chip to play 24 tunes in sequence as one of the options. There are no printed circuit boards and all wiring is point to point and supported by the inner and outer pyramids which are also the supply rails.
A whatchyamacallit 1980's Not sure what to call this thing made about 30 years ago.
It used some sort of transistor oscillator (now covered in tape) driving an E core iron electromagnet at >20 kHz. It runs from a small 9 V battery and has a reed switch in it to turn on. You bring the box of matches with a hidden magnet just visible here close to turn it on. It induces a current in the coil of unknown turns to drive two LEDs on a smiley face. The LEDs still light up about an inch away. It still works but I have replaced the LEDs after the leads broke and replaced some of the tape. So, remote signaling and remote power transfer 1980 style!
Power transistor as a LED 2006 This unusual effect shows how a current between base and emitter makes a semiconductor junction emit light. To show this one needs to expose the silicon chip in a NPN power transistor such as a 2N3055. With the 2N3055 base negative and emitter positive 11.4 V current 400 mA are drawn and the junction lights up. The chip is 2 mm wide.
Camera has 2 sec exposure in darkened room with a plastic magnifying lens. |
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This page was last updated January 19, 2011
