Hi All. Thank you for very interesting thread and useful info.
I am really exited about high power LEDs and I wanted to replace my existing halogens with them for quite some time.
What I have right now (see photo) is a system with 10 50W/12V halogen bulbs in SERIES. I have bought an ordinary 12V track lightning at Home Depot and gutted it by removing all inverters and connecting bulbs in series. I am feeding lights with 120AC and everything works perfectly for more then 10 years now. The main reason for removing switching AC inverters was my fear that low quality inverters will interfere with my audio system.
I am not complaining about 0.5KW dissipation, because my audio system dissipates similar amount of heat.
I have two questions:
1. Can I connect LEDs in series and drive them with linear constant current source? There is no need for me to drive each LED individually and it should not be difficult to build 40-50V/3A constant current power source.
2. What LED is the best (or approximate) equivalent to the 50W flood (wide angle) halogen? I really like cool (daylight) spectral temperature. I want just a light source LED like you guys showed on the photos, not the ready-made bulb. I hope to design the fixture myself.
Thanks a lot.
I am really exited about high power LEDs and I wanted to replace my existing halogens with them for quite some time.
What I have right now (see photo) is a system with 10 50W/12V halogen bulbs in SERIES. I have bought an ordinary 12V track lightning at Home Depot and gutted it by removing all inverters and connecting bulbs in series. I am feeding lights with 120AC and everything works perfectly for more then 10 years now. The main reason for removing switching AC inverters was my fear that low quality inverters will interfere with my audio system.
I am not complaining about 0.5KW dissipation, because my audio system dissipates similar amount of heat.
I have two questions:
1. Can I connect LEDs in series and drive them with linear constant current source? There is no need for me to drive each LED individually and it should not be difficult to build 40-50V/3A constant current power source.
2. What LED is the best (or approximate) equivalent to the 50W flood (wide angle) halogen? I really like cool (daylight) spectral temperature. I want just a light source LED like you guys showed on the photos, not the ready-made bulb. I hope to design the fixture myself.
Thanks a lot.
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getting to the equivalent light output of a 50w halogen flood or spot is THE issue.
there are some multi chip "light engines" out there... asian imports too. But driving them is not a simple supply, otherwise you have fried LEDs. They are expensive, and it doesn't seem like the price vs. power cost has quite yet hit the tipping point. Seems like it is getting closer, but maybe a few years off in the future... unless you want to spend the $$...
_-_-bear
there are some multi chip "light engines" out there... asian imports too. But driving them is not a simple supply, otherwise you have fried LEDs. They are expensive, and it doesn't seem like the price vs. power cost has quite yet hit the tipping point. Seems like it is getting closer, but maybe a few years off in the future... unless you want to spend the $$...
_-_-bear
Bear,
The fans in those Philips lamps are VERY quiet but if you can't find those in the U.S. maybe you can find these from Osram -
OSRAM
particularly the last two 10w ones...
The light is stunning and at 3000K, definitely not blue! No fan but a fair bit deeper than a standard dichroic lamp.
John
The fans in those Philips lamps are VERY quiet but if you can't find those in the U.S. maybe you can find these from Osram -
OSRAM
particularly the last two 10w ones...
The light is stunning and at 3000K, definitely not blue! No fan but a fair bit deeper than a standard dichroic lamp.
John
I have been getting a server error from the Osram link. Anyhow, over here, Sylvania is the Philips lighting brand:
OSRAM SYLVANIA - Professional LED
But I'd love to know which particular models you found give the best light quality (CRI). Of course we run on 110v and you probably have 220v.
Sylvania's parent company is Osram, and Osram itself is owned by Siemens, not Philips.
The LEDbulbs in the link you provided have a CRI of 95, that's pretty close to daylight (100). For comparison: a CFL from a well known brand typically is ~85.
The CRI won't be affected by mains voltage.
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The heat problems are being solved. See LED COB led, COB LED module, chips on board, ceramic board COB LED, COB LEDs, COB led light engine, chip on board LED packaging, China manufacturer, LED COB strip, white LED, COB LED component for one way to solve the problem.
That doesn't solve the heat problems, it only makes it easier to mount the LED to a heatsink. Most LEDs are below around 20% efficient, especially for warm-white emitters, which means for a 10 watt bulb you have to dump ~8 watts of that as heat. The only way to 'solve' the heat problem is to make LEDs far more efficient.
Interesting read on the pitfalls one encounters comparing "conventional" light sources with made-for-LED luminaries: http://www.colorkinetics.com/support/whitepapers/Evaluating_Light_Output.pdf
The power of the LED isn't in its electrical efficiency alone, in the right fixture optical efficiency takes it to another level.
Eye-opening is the example used to explain why a 177 lumen LED-fixture can produce the same light intensity on the "task surface" as a CFL fixture using a 700 lumen lamp.
The power of the LED isn't in its electrical efficiency alone, in the right fixture optical efficiency takes it to another level.
Eye-opening is the example used to explain why a 177 lumen LED-fixture can produce the same light intensity on the "task surface" as a CFL fixture using a 700 lumen lamp.
That paper sounds like an attempt to explain why LEDs are not as bad as they appear to be to people who are not lighting technicians. The 'wasted' light from other sources gives general illumination, whereas LEDs are very directional. The result is that an expert can 'prove' that LED downlighters can properly illuminate a corridor, but normal people will still find it dark and unpleasant. Is the aim of corridor lighting to light an imaginary plane 30in above the floor, or to help people recognise each other as they pass or look for visual clues in their faces as they converse?
The building I work in has most corridors lit by small recessed fixtures with a CFL and you wouldn't guess that the 18 W PL-C lamps inside put out 1200 lm each. What you see on the walls and floor looks like less than half of all that light made it there... This light didn't end up as "general illumination", as you put it, it was wasted as it never left the fixture.
I agree with you that LED fixtures that shed the same low amount of light on the surface would look dark and unpleasant too.
But being able to achieve the same light intensity on a surface with much less total emitted light, because less is going in the wrong direction, is what it's about. And that is why I believe that LEDs are eventually going to supersede other light sources.
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It's not fair to judge the cost of LED lighting by the prices in stores. Take a look on eBay; $4 will get you a 3 watt MR16 12V lamp, shipped. I bought a couple to try out as bike lights. The beam pattern is unsuitable (too broad and even), but usefully it will operate from 6V. And it wouldn't take much RTV to make it waterproof. Not a bad way to experiment with high(ish) power LEDs; you get a 3W star emitter and a huge heatsink. The driver board was gooped into the base, but probably could be extracted. The input full-wave rectifier could be removed for DC operation, and there's a fairly good chance that the driver chip has a pin that can be used for dimming via PWM or a pot. I'm sure the beam pattern can be improved by replacing or modifying the optics.
The sensible solution to bike lighting is to just buy a complete set from eBay or Dealextreme; under $50 will get you something comparable to what bike stores sell for triple that amount, with a nice housing and Li-ion battery back and charger. But I have two bikes, and I want something I can leave on the bike permanently that's ugly enough it won't get stolen, and that includes taillight and maybe an amber warning flasher for unusually dangerous conditions like snowstorms. So I've ordered various bits from eBay, including a viciously bright Cree XM-L, although I suspect regular 3W LEDs will be good enough for most riding.
The sensible solution to bike lighting is to just buy a complete set from eBay or Dealextreme; under $50 will get you something comparable to what bike stores sell for triple that amount, with a nice housing and Li-ion battery back and charger. But I have two bikes, and I want something I can leave on the bike permanently that's ugly enough it won't get stolen, and that includes taillight and maybe an amber warning flasher for unusually dangerous conditions like snowstorms. So I've ordered various bits from eBay, including a viciously bright Cree XM-L, although I suspect regular 3W LEDs will be good enough for most riding.
I've had a Philips 25-watt equivalent LED bulb (model #5E26A60) in use here for six months now in a lamp used for a hallway that needs to be lit all night. Cost was $19 + tax*. I also bought a 15 watt equivalent LED bulb made by Feit Electric (model #BPA15/LED, the newer verson with the white plastic "collar" - I bought it at a local grocery store!). Cost was $8 + tax. I wanted to take a couple quick pics of them for comparison purposes but haven't had the time to set them up properly for such a photo.
The Philips emits a clean white light but not so white it is unnatural, while the little Feit bulb emits a vaguely bluish white light, similar to those GE "Reveal" incandescents. I definitely prefer the Philips for interior use while the Feit is used for accent lighting in my mancave in one of those uplights (basically a black metal can that's open at the top) while watching movies via the HT system.
Heat issues: the Philips' metal housing with internal metal fins becomes very warm after just a few minutes, and can only hold my finger against it for a few seconds. The Feit became only vaguely warm, even after a several hours have passed by.
Next LED bulb I'd like to try is either: one of those Philips 40 watt equivalent bulbs that utilize that strange looking segmented yellow filter system which hopefully provides a "warmer" light than the Philips I own now, but the prices for them are a bit breathtaking so that may take awhile; or this bulb with an interesting UFO-like lens system, much cheaper but not sure of its quality, sold at a local home improvement retailer under their own house brand.
* price dropped to about $13 a couple months ago
The Philips emits a clean white light but not so white it is unnatural, while the little Feit bulb emits a vaguely bluish white light, similar to those GE "Reveal" incandescents. I definitely prefer the Philips for interior use while the Feit is used for accent lighting in my mancave
in one of those uplights (basically a black metal can that's open at the top) while watching movies via the HT system.Heat issues: the Philips' metal housing with internal metal fins becomes very warm after just a few minutes, and can only hold my finger against it for a few seconds. The Feit became only vaguely warm, even after a several hours have passed by.
Next LED bulb I'd like to try is either: one of those Philips 40 watt equivalent bulbs that utilize that strange looking segmented yellow filter system which hopefully provides a "warmer" light than the Philips I own now, but the prices for them are a bit breathtaking so that may take awhile; or this bulb with an interesting UFO-like lens system, much cheaper but not sure of its quality, sold at a local home improvement retailer under their own house brand.
* price dropped to about $13 a couple months ago
The only way to find out about the quality is buy it and put it into demanding use.
By demanding use I mean usage in which the lamp gets to go through quite a few cycles, from fully warmed up to fully cooled down. From experience I know that lamps that stay on long in combination with a limited number of cycles usually last much longer than the specified average lifetime, but those that cycle a lot don't even survive half that... Especially CFLs that start in cold cathode mode (instantly on without pre-heat) suffer from every ignition. Obviously LED bulbs don't ignite like a fluorescent lamp but still, every cycle will have an effect on the lifetime of the electronics...
By demanding use I mean usage in which the lamp gets to go through quite a few cycles, from fully warmed up to fully cooled down. From experience I know that lamps that stay on long in combination with a limited number of cycles usually last much longer than the specified average lifetime, but those that cycle a lot don't even survive half that... Especially CFLs that start in cold cathode mode (instantly on without pre-heat) suffer from every ignition. Obviously LED bulbs don't ignite like a fluorescent lamp but still, every cycle will have an effect on the lifetime of the electronics...
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I saw that $199 figure and assume they misplaced the decimal point, or that price is for a box of multiple bulbs (this past summer I was at a store which sold LED lamps and walked by another customer who must have had at least ten
LED bulbs priced at $22 in his cart, so offering a multi-pack option wouldn't be surprising).
I saw that $199 figure and assume they misplaced the decimal point, or that price is for a box of multiple bulbs (this past summer I was at a store which sold LED lamps and walked by another customer who must have had at least ten
There are too many 9s in there to have misplaced the decimal point alone. The price is probably meant to be $19.99. The shipping weight is specified as 6.4 ounces (182 g), and I can't imagine that being more than one bulb + packaging.
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Couple questions:
* if an LED light source is treated well (good circuit design, no power surges etc) and it is simply used as intended, what finally causes it to fail? Do the materials it uses breakdown due to age, electrical causes or both?
* what is the main "ingredient" of the typical LED used in residential/commercial lighting? Is this something that the planet has in large quantities or will we be hearing stories in 50 years of LEDs being abandoned in favor of fireflies?
* if an LED light source is treated well (good circuit design, no power surges etc) and it is simply used as intended, what finally causes it to fail? Do the materials it uses breakdown due to age, electrical causes or both?
* what is the main "ingredient" of the typical LED used in residential/commercial lighting? Is this something that the planet has in large quantities or will we be hearing stories in 50 years of LEDs being abandoned in favor of fireflies?
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