LM317 to drive 3W HPLeds?

[Mattie en rose]

Hey ppl, so thanks to this place I built my first 425mw red laser and have since had much fun with it. My next project is going to be a 1w blu diode in a mag light...

My current question is, can I build a couple LM317 drivers to power 3W red HP leds? I'm building a new hydroponic system and want to diy my lighting, as premade lde lighting is waaaaay to expensive... If I can use this driver, how many leds could be powered off one driver? I plan to use 6v 1000ma power packs to power the drivers... The ratings on the leds is forward voltage 2.0-2.4 @ 900ma..

Thanks everyone!

 

[Sigurthr]

Yes you can run a single LED at 2.5V/900mA off a LM317 fed by a 6V/1A power supply. You will need to heatsink the LM317 though and you can't use more than one LED per LM317 (they can only handle 1 amp each).

 

[Cyparagon]

Hydroponic on what scale? Driving them all separately will be very inefficient. Are you comfortable with mains voltages? Rectifying mains and powering a long series string would be far more efficient. This can be done with <$5 in parts.

 

[Mattie en rose]

It's just a little 8-plant table top size for growing my common used herbs and such...

It will have 9 leds total, 6red and 3 blue... I never thought of mains power, which yes I'm fine with.. I pondered using a step down transformer but figured id use the power packs I have.

But if u could point me in the direction to build a circuit to drive them all off mains power, that would be great... I plan to mount the leds in a custom reflector hood, and each led will have its own heatsink, and the unit will have fans actively cooling it.

 

[Benm]

If they all require the same amount of current i would wire the whole lot in series indeed, and then build a constant current driver from a mains power supply at suitable voltage. U can use this circuit as a driver: Merghart.com - 2 Transistor current source

The only thing you would need is a mains adapter/supply of suitable output voltage to drive the series string... and probably heatsinking for the transistor.