looking to learn more about them and eventually wire up a handful of lights for a 12v project. Anybody know where to start aside from google?
-=bmacd=-
-=bmacd=-
any LED light guys here?
- Thread starter bmacd
- Start date
sygyzy
Lifer
- Oct 21, 2000
- 14,001
- 4
- 76
too much!! How to wire them, which resistors to use, diodes, how to wire them, where to get them inexpensively, pretty much a bunch of newbie FAQs.
-=bmacd=-
AgaBoogaBoo
Lifer
- Feb 16, 2003
- 26,108
- 5
- 81
That's going to be a big resource, other than that, ask around, Eli knows what he's talking about, at least till you talk about growing plants
Need more details - what exactly did you have in mind? How much power do you need, etc.? Do you want to achieve any special effects?
If you need bulk light production, then you're best off using specially made high-power LEDs.
This is a picture of an Xbox fitted with 3 LEDs. In this case I used 1W LEDs - 3W and 5W versions are also available, and are correspondingly brighter.
One of my earlier LED lighting projects
If you need bulk light production, then you're best off using specially made high-power LEDs.
This is a picture of an Xbox fitted with 3 LEDs. In this case I used 1W LEDs - 3W and 5W versions are also available, and are correspondingly brighter.
One of my earlier LED lighting projects
I was going to build a license plate frame for my motorcycle with integrated brake and turn signals. I was planning on using amber LEDs for the turns, and reds for the brakes. I'm not sure if it's possible to utilize the LED's like a dual filament light bulb...as in having the brake lights also function as daytime running lights. Might throw some white LEDs in there just to increase visibility.
-=bmacd=-
shilala
Lifer
- Oct 5, 2004
- 11,437
- 1
- 76
Dig around in here, there's everything you need to know...
http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng
http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng
How much are you willing to spend? I don't think 5mm will be powerful enough, but SuperFlux might do the trick. Luxeons are probably going to be a good deal more expensive.
Check out www.lsdiodes.com there is another good site that I can't remember, if I think of it I'll post it. Oh, and www.sickmods.net has a good calculator and intro for finding the right resistors and such.
get a digikey catalog....they're free...you can sample to your hearts content...hooray for engineering samples
Interesting idea.
The first thing you need to do is find some suitable LEDs. My experience with ebay LEDs in general has been dissapointing. Though cheap they are of poor quality, and unreliable. My personal preference would be to use LEDs designed specifically for vehicle stop/turn lights. These are designed to be the correct colour, have a suitable beam shape and be tolerant of vibration.
Most cheap LEDs have super-narrow beams (because the narrower the beam the higher the brightness, and the bigger the numbers that can be claimed in the specs), which are useless because they can only be seen directly head on, and not from any angle.
In this case a bank of medium power LEDs would be the best solution. E.g. A bank of 20 of the HPWT-DD00 superflux LEDs from here should make a satisfactory brake light. It should be possible to arrange for 10 of them to illuminate at half brightness to act as tail lights.
There are other problems that can arise with large banks of LEDs. Heat is a big problem, especially if you are making grids of LEDs. The high performance LEDs above have outstanding thermal performance, but at the same time they are a lot more powerful than normal LEDs. You will have to have some ventilation to keep them cool.
Another problem is vibration - the LEDs will have to be soldered to some sort of circuit board. Don't be tempted to just solder wires to the leads, the vibration from road use will crack the joins before long. Again, another advantage of the superflux LEDs is that their 4 pin construction resists vibration.
Electrical connections
LEDs are current operated devices - you need to supply the correct current, as they don't limit the current themselves.
The equations (1) R = (Vs - Vf) / If, and (2) Pr = (If ^ 2) * R can be used to determine type of resistor required:
R = resistor required (Ohms)
Pr = Minimum power rating of the resistor (Watts)
Vs = Power supply voltage (Volts)
Vf = LED forward voltage (Volts)
If = LED forward current (Amps)
So, if you were making a brake light out of super flux LEDs for a bike - I would connect the LEDs in strings of 4 in series. This would give 5 strings - each string would be 4 LEDs and 1 resistor.
Vs = battery voltage (approx 13.8 V with engine running)
Vf = LED Vf * No. of LEDs (2.5 V * 4) = 10.0 V
If = 0.06 A (Rated current is 0.07 A, but as you'll have lots of them together, best to slightly under-power them so they don't cook)
Using Eq (1) we get R = 63 Ohms - the closest resistor greater than that is 68 Ohms.
Using Eq (2) We get Pr = 0.25 W. We need a resistor with higher power - 0.5 W is the next highest rating.
So to make 1 brake light you'd need 5x 68 Ohm 0.5 W resistors.
These resistors will get very hot during use - so it's best to put them away from the LEDs so you don't overheat them LEDs.
I see someone mentioned luxeon stars - these are great LEDs, but have a full 180 degree beam width - this means that most of the light comes out of the side, and not the front. Best performance requires a reflector and lens. They also use much higher currents so your resistors need to be capable of handling the power required - this usually means special high power resistors. The LEDs also produce a lot of heat, and should be attached to a heatsink - on old CPU heatsink is fine, although the area for stciking the LEDs on is a bit small. Perhaps a better option is a chipset cooler on each LED. Because the base of the LEDs are flat you just glue them onto the heatsink with a bit of thermal epoxy. Then just solder your wires to the top side of the LED.
If you can deal with the higher electrical and thermal powers of the luxeons, they are probably an easier option than the superflux - less soldering, fewer connections, no need for a circuit board, etc.
Because the Luxeon stars are so much more powerful than superflux - you'll probably only need 4 of them for a brake light (assuming the standard luxeon version - the Luxeon III is 3x as powerful, you could use 1 or 2 Luxeon IIIs if you wanted - note that luxeon IIIs *must* go on seperate heatsinks, and the heatsinks cannot touch or be connected to each other electrically).
Using equations 1 and 2 from above:
Vf = 2.5 * 4
If = 0.3A (rated power is 0.35 A, but best to underrate slightly)
You get would need a resistor of 15 Ohms, 2 W power.
And again for 2 Luxeon IIIs
Vf = 2.95 * 2
If = 1.25 A (rated power is 1.4 A)
Resistor = 6.8 Ohms, 10 W (Note that this is a very high power resisot and will get very hot during use - it will burn you if you touch it while it is running. Make sure that it is safely placed).
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