LEDs respond very well to strobing. They probably even prefer it to constant on.
LEDs respond very well to strobing. They probably even prefer it to constant on.
Led color and brightness consistency is directly linked to die heatsinking properties. The old GAP T1-3/4s were good for 20,000 hours to 50% degradation, but not the new GN ones when ran at rated currents. The graphs are freely available at the Rensselaer web site below if you do some digging. Its a disgustingly short lifetime if you cook a yellow with blue phosphor white led. They go blue, then they go dim.
Whats sad is many LED makers pulse the leds during testing for that nice, but otherwise unobtainable, zero die temp rise during testing.
See below:
Steve
http://www.lrc.rpi.edu/programs/solidstate/
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When I still could have...
CFL's used to be really poor but some are good now. My entire house has been on CFl's for the past 2 years and we have no problems although I do always go for the 18W spiral type as the output is never quite as high as claimed even on the good ones (these are claimed to be 75w but I treat them as 60's). I like GE's as they're really white like halogen - I'm not too keen on the yellowy ones that try to pretend to be traditional bulbs.
I once tried an LED GU10 bulb in a downlighter I have but found it dim. In fact way to dim to be useful.
The CFL's are worth using if you get the good ones as they can cut your electricity (lighting) bill to 1/3rd of what it was before on tungsten.
I personally await the day that we see the high power LED's avalailable as bulb replacement. I have some sidelight bulbs in my car based on a Luxeon LED and they're rated at 1 watts:http://www.hids4u.co.uk/501-led-high...p-1-pr-86.html
The output is immense for a sidelight - many times a traditional sidelight bulb and pure white. They won't light the road (they are a sidelight after all) but do look awesomely bright. I can see the day when Luxeon's could be powering our lighting sockets for maybe 7 or 8 watts.
I replaced the 100W lightbulb in my room a while ago with a home built led array.
It's quite hard to explain how cool a room lit entirely with leds is, and not just because they're leds. The light just seems better.
Used Red, Green, Blue and White leds so i could have any color
Its a bit of a mess, but it works well.
It's driven by an ATMega doing PWM with 4 FETs, one for each color.
Here's a video of it working
http://www.youtube.com/watch?v=1jH_wRJW5vU
It's made up of
9x 3.2W White 176lm
10x 1.5W Red 67lm
4x 5W Green 147lm
9x 2.5W Blue 30lm
Cost maybe $70 in LEDs at the time.
I don't run it with them all at 100% because 86W of LEDs is a bit too bright for the room.
Most of the time i run it around 35W, using all the white and a little red + green.
Last edited by Psi; 10-03-2009 at 15:59.
That's really neat.
So you've got a theoretical max of 2700 lumens. That's only 150W incandescent equivalent. 31lm/W... I expected it to be higher... some halogens can top that. This amount of light can be made by a 42W CFL or a 35W metal halide.
Doc's website
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yeah, logitech harmony remotes are really great for that sort of thing
Lumens takes into account eye sensitivity, so ya can't really compare the watt per lumen efficiency of colored leds with a white CFL or white metal halide.
Using white leds for 2700 lumens you'd only need...
2700 lm / 176 lm = 15.3
15.3 x 3.2W = 48
So you'd only need 48W of white leds to get 2700 lumens
Which makes more sense in context of 42W for CFL or 35W for metal halide.
I'm pretty sure more efficient white leds exist than what i used. I think there are some that sit between CFL and metal halide in efficiency.
Last edited by Psi; 10-02-2009 at 14:28.
Yes, but the efficiency of the colored ones must be pretty low. I'd expect a 5W green for example to be substantially brighter than a 3.2W white.
Cree has a few (3 watt?) that do over 100 lm/W if you run them lower... at 1W
there are 20 - 100 watt white leds out there up to 6000 lumen
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