1w led driver help!!

[mlandicini1036]

I have been looking all over for help on this and get only half the answer here is what I am doing.
I am looking to put 3-1w hight brightness leds in a series and need to figure out how in the world I can do it.
I know i need to build a driver and not sure how to do so, I know i need a lm317 I think that regulator will be finr to keep the leds at a constant volt. I am using a 12v power supply. I do not know what size resistor I need and how to wire it up can some one please give me the full help I am looking for thanks.

Matt

 

[Torben]

What are the current and forward voltage ratings of the LEDs? Failing that, what colour are they?


Torben

 

[mlandicini1036]

im sorry I forgot to post that i believe its 4.5 im using the leuxon (spelling?) stars really what I want to do is they come in 3 different colors in one led mod, rgb I want to use the red/blue on each head it looks really intresting to start a project. But before I get that ahead of myself i want to build a driver for just 3 in a series either red or blue but like i said I believe its 4.5 soo correct me if im wrong but thanks for the help if you can provide it to me
Matt

 

[mlandicini1036]

bump please still need that help

 

[Torben]

Do you at least have a part #? You can't just say they're "Luxeon"; that's the name of a line of LEDs, not a model or part.

Anyway, if the forward voltage is 4.5V, you're never going to get 3 in series to work on 12V. Voltages add up so you'd need at least 4.5 * 3 = 13.5V, plus a little headroom for the current limiting resistor. There are methods of boosting the voltage (charge pumps etc) but you'll find it much, much easier to put 2 in series with 1 parallel. That said, 4.5 doesn't sound right for the voltage or for the amperage. Taking a random shot at one Luxeon datasheet (the Luxeon I, red, 1 watt, 385mA/2.95Vf) you could indeed put 3 in series on 12V, with an 8.2 Ohm resistor to limit current. That resistor is going to melt unless it's hefty enough to dissipate over 1 Watt, though. I'd suggest at least a 2 Watt resistor and be prepared for the fact that the whole thing will be quite inefficient.

For better ideas, check out this link: https://www.electro-tech-online.com/threads/driving-luxeon-leds.2570/

Also try googling "luxeon led driver".


Regards,

Torben

 

[Oznog]

Linear regulators are very inefficient. You'll lose the same amount of heat whether it's a transistor reg or just resistors. The transistor ones, however, can be regulators so it'll be relatively insensitive to changes in source voltage. If the 12v is a car or rechargeable batt, that's an issue.

A buck reg is much, much less loss. It runs cooler. Most are designed to be fairly insensitive to changes in source voltage. Plenty of places to buy cheap 12v LED drivers like that.