LED grow light

[sdistin]

I wanted to give my herbs (real herbs...for eating) an early start this spring without paying a ton for a commercial grow light, so I built one. On a sheet of aluminum (9x12x.125" or 22.5x30x.3cm) I glued 23 three-watt LEDs with thermal epoxy.



The LEDs' wavelengths were chosen to correspond to the absorbence of plant pigments, especially chlorophyll A and B. There's no point in giving a plant green when it's just going to spit it back out. The wavelengths I chose were: 400-405nm, 450-455nm, and ~650nm. The LEDs are wired in series and powered by a single driver at 700mA. It makes an eerie glow.

I stuck a heat sink from an old amp onto the top hoping that would be enough to dissipate the heat - it wasn't. So I had to do some active heat dissipation. I had the computer parts fairy bring me some CPU heatsinks which I powered with a 12V DC adapter and stuck to the plate.

That did the trick! It barely gets above room temperature so I can run it indefinitely.

I may add more blue-violet LEDs and some more diverse red wavelengths but for now, any plant I've put under it seems happy.

 

[Cyparagon]

Neat. How warm did it get with the amplifier heat sink? Which driver did you use?

 

[Lazerbeak]

Awesome project Sdistin. Checked out some LED grow light setups a while back. Pricey and your DIY probably performs way better. Happy Plants

:gj:

~ LB

 

[sdistin]

Neat. How warm did it get with the amplifier heat sink? Which driver did you use?

Hard to say for sure. Well above body temp and enough for me to be worried about the life of the diodes.

I was off when I said 700mA, that's the current I would have preferred. This is the driver I used, which had enough voltage for all of the Vfs of the LEDs combined. If one were so inclined, or less lazy, multiple drivers could be used.