I've been playing with LED's to light up my house. I've done a few experiments and figured out what works and where for me. I just wanted to share some of it.
OK so LED's are bloody bright when you look at em, but bring em and install in a fixture and not only is it awful looking, its also bloody dim. Why ...
1 word - Viewing angle. There is more ... there are misleading terminology, incomprehensible jargon with them declaring their specs in Mcd when the world talks about watts etc etc etc ...
So what's the skinny.
Viewing angle - you draw and imaginary cone with the top angle of the cone being the angle they say for an LED. 15 degree is a common one, as is 30 etc etc ...
A light bulb in a can fitting - our standard kitchen light is a whopping 180 degree viewing angle. A bulb hanging form the ceiling with a mirrored ceiling is a 360 degree. Remember this is solid angle not 2d. here 90 degree X 4 is not 360 degrees. Its closer to 6 X. Lets call it 6 X 90.
Then a 100 watt bulb when new puts out about 135,000 mcd - this is courtesy google. Of course no one has a mirrored ceiling, and effectively we light up a nice 60-70 degree pool below the light, and the rest is wasted. So with a 60 degree LED with a 135,000 mcd is almost the same as a 100 watt bulb.
Now for the kicker. A light bulb makes 10-15 times more heat than light. Your light is say 3-5 watts worth, the rest is heat - and in winter it helps, but hurts in summer. I'll still say its helpful a little, cos we use lights at night, but just turning up the thermostat is better, cos light bulb's are near the ceiling, we need hot air by us, not @ the ceiling.
Anyway 135,000 mcd 60 degree LED = 100 watt bulb for 90% of bulb uses.
So what now -
Enter the magic 30,000 mcd LED - this one -
http://www.ebay.com/itm/100PCS-5mm-Super-Bright-Sunny-Warm-White-LED-Lamp-30-...I have bought a few 100 from that seller, and I am impressed with their quality. @ 3.60 for a 100 warm white LED to your door it is a steal. Nothing compares ... they have some sorta wholesale deal on now. I bought me 400 more. I have like 200 assorted ones left over from before but rapidly running them into fixtures etc. Used 45 today. These are 25 degree - but it wont matter once you get through this whole thread.
OK so you now have a dime bag of LED's what next.
LED's have a Forward voltage. Vf. Apply that and they light up. They have a If - forward current - exceed that and they go poof.
Those guys like 3.4 - 3.6 Vdc and 30 ma. Actually they run fine on AC, but DC is better they dont flicker ... They dont with ac too ... but I would do dc. Safer and better.
OK so how do you feed them 3.4 v and give em 30 milliamp and no more.
Enter the cheapo Dc adapter (lap top charger or other charger adapter power supply of any kind). Smaller ones are better - they can be hidden easier.
So you get an adapter - 12v is very common - from the local goodwill store. I have a few grab bags - 3-4 in each for $2 I have bought.
Pick one - a small one is usually 12vdc and say 500 ma.
Your led is 3.3 vf - you string up 3 its a 10v - the 2 v that is left over - you put a 100 ohm resistor in series and you have automatically limited the current to 20 ma. Done.
The calculator is here for other voltages etc.
http://led.linear1.org/led.wizSo back to our example - 3 LED's putting out 30,000 mcd = 90,000 and you're running 20 ma ... your adapter is capable of running 25 strings of 3 each. 22 million mcd.
Get a wafer board @ radioshack, solder in 3 X as many as you want leds the right way in series and you can use 1 big 100 ohm resistor to get all of em current limited properly.
I have noticed these make excellent under cabinet lights if you install them in one of em little wood boxes with velcro, they make excellent lights in torchieres - cos those light up the ceiling so you never see the bulb, and other hidden fittings like inside lamp shades or behind something.
They suck as overhead kitchen track lighting, and as bathroom lights. In short - If you can see the light bulb - they wont be the best choice.
Now the 25 degree - obviously the torchieres dont care you can direct them into the room a bit. Anywhere where there is some flexibility to turn the fixture or turning the led's in the fixture will get the part you want well lit. I put an angled wedge in the under cabinet fixture. Its nicely directed to where you need, and you can move it too. It runs cold. They can be touched after having been on for hours. They are cold.
Now LED's dont like being left on for over 16 hours at a time. You can turn em off - even 2-3 min, and they can be run again for another 16 hrs.
I hate those CFL's and LED's have been proven to not give any $$$ to Al Bore. There is a imported component yes, the LED's, the wafer board too probably, but the adapters are an industrial waste tossed out by people getting bored of their phones or what not. Biggest component is that and labor. I'll post pics when I finish the yellow/white bendable hybrid array I am working on.
Cool.
Srinath.
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