1W LED's

What about longivity of the bulbs? If the bulb is 1/3 the price, but needs replacing 4 times as often...

when they get in that neighborhood it'll be worth considering. right now its more like 8-10 times the price

Overclocked said:

Or I could have gotten lucky and these could have been mixed up with 5W LEDs...

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Have you got a close-up photo of the LEDs? The 1W LEDs have one small die in the centre of the dome. The 5W ones have got 4 dies in them usually looks like 4 squares.

I don't know about LEDs but I read an interesting study about the cost of energy vs lamp life time. Doubling the lamp life reduces the efficiency by a quarter - they could make the average bulb last 2000 hours rather than 1000 hours but the extra running costs would not make it worthwhile.

DMX512 system

i have same of DMX512 program in c51 .if somebody want can add my MSN logto@hotmail.com

justDIY said:

wait, 100w equivilant cfl's are only $1 ea in Connecticut, is that some sort of government rebate program or social welfare? Damn, what store is this - I need to grab some!

the 23 watt cfl I have (claims to replace a 100w bulb) outputs 1600 lumens, that's roughly 70 lm/w. The best rated cool white rebel is 180 lm @ 2.38w (700ma * 3.4v) which is roughly 76 lm/w. To match the output of my $8 CFL, I'd need 9 rebels, at $6.60 ea that's $60. I think I'll stick with compact fluorescent for now. It is good to see the numbers are getting better, but lumens per watt isn't the metric the public will judge new lighting technology by. It's lumens per dollar:

rebel = 3.6¢ per lm
cfl = 0.5¢ per lm

The reason Edison is still rich with his hot-wire bulb = 0.016¢ per lumen ... that's right, $0.00016 per lumen (figuring 25 cents per bulb)

edit:

oh, don't forget to include energy used by the driving circuitry - cfl's have very efficient offline smps powering them. the same technology is just now becoming available for leds. running leds using resistors or linear regulators puts their efficiency numbers back in the stone age with the hot wire bulb.

edit2:

if your heatsink didn't even feel warm, then you have a problem with thermal coupling. most "star" type leds have a rather high thermal resistance, although it's better than the olden days. new ceramic composite leds have a much lower resistance (rebel, ostar, lamina) - they're the ones you can really push. you need a laser IR thermometer or a well placed thermocouple to really measure the junction temperature - lumileds has some data about this in their thermal management white paper.

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yeap! They Were orignally $9 with a 5 dollar rebate (instant) The total came to like $3.99 for a 4 pack of 100W Bulbs made by a name brand company! I got em at BJ's wholesale club.

I was wondering if the LED was even making contact with the Star, it didnt look like it from what I could see. Im going to have to unsolder the connections and have a look, but I noticed the star is made from Aluminum, which is a OK conductor of heat (copper is better).

I just found a better project for those 1W LEDs...Screw the indoor Idea! We just ripped out our sidewalk lights, theyve been here for a couple years. So I figured with the 3 I have left, I can make some sort of light thats waterproof and one that can be stuck in the ground (kinda like those solar lights, but better!) I dont know if I should use battery or start with a offline SMPS. I could always build a solar system with rechargable batteries..and then use a SMPS to power the lights for the night.

Then again, Id be afraid of someone hjijacking the lights.

ADD: My math was wrong, but Im not far off. Vf is actually around 9.45V! So Lets use the rebel version that gives 485 Lumens @700mA. The LED uses 6.62W to emit 485 Lumens, So in order to produce 1100 Lumens, You would need about 3 Rebels, which brings the total power to 19.86W. So it seems LED tech is about on par with Fluorescent Lighting, But the expense is just too much. Now if these LEDs were about 50 cents each, then it would be worth it, but at $30 per LED + the driver is a bit expensive...

Why do high power LEDs cost so much? What makes them different?

you're still calculating the power wrong. using the datasheet, to achieve 180lm (the best rebel there is), it states 3.4v at 700ma which is 2.38 watts. I don't care what anyone else has printed on their web sites or in sales literature, I always go by the manuf. datasheet unless it is proven wrong, and so far, Philips is pretty accurate with their datasheets. 180 lumens divided by 2.38 watts equals 75.63 lumens per watt.

To get your target of 1100 lumens, you'll need to divide 1100 by 180 which equals 6.11 round that up to 7 rebels. Now to calculate the wattage, 7 rebels times 2.38 watts equals 16.66 watts. Since watts = watts it doesn't matter if Vf is parallel or series, 7 rebels times 3.4v each equals 23.8v times 700ma = 16.66 watts.

Seven rebels at $6.60 (current small order price from Future) is $46.20. Like you point out, have to add the cost of a suitable driver, and it gets pretty expensive. Having a heatsink machined to keep 17 watts of leds cool would cost even more. Especially designing one to fit in the confines of a standard edison base lamp.

Which leads to the real 'sticker' ... All this math assumes the junction temperature remains 25C ... any increase in Tj and efficiency takes a nose dive.

High power leds are cheaper than any other type of led. You have to consider the lumens per dollar metric when comparing pricing. The top binned rebel is a rare item, rumor has it a LOT of them are going to the Big 3 automotive market, and even more are going to the military. Despite huge demand the price is still pretty cheap. Consider a 5mm white led which may give you 1 lumen costs ten cents. One hundred eighty 5mm leds would cost you eighteen dollars, and think of the heat they would generate and power they'd take!