tinkerer's led ufo light

stevemac00November 11, 2013

For my initial foray into hydroponics and indoor gardening I have tomatoes growing under HPS. I've had a few blossom end rot and other issues so it's not been without problems. But fortunately light hasn't been much of an issue except the backside of the tomato plants get almost no light. What I'd like is some supplemental lights to hang and move around to keep the plants growing uniformly.

I like the promise of LED but don't want to spend much money for something that will be obsolete in a couple of years. I read some articles on the web and started my own tinkering. Here's how I started.

A single LED array from Cree that puts out roughly 5000 lumens at about 55 watts. I don't have anything to measure so I can't verify but when I first plugged it in I was looking at it from the side and I had a black spot in my vision the remainder of the afternoon which was scary.

Here's a photo of my setup with the HPS currently at 400 watts. You can see the bright white spot of the LED in the middle. It's obviously brighter than the HPS at a close distance and effectively lights up the backside of the plant.

Here's a link to Cree for the "bulb" I used: CXA2540. As you can see they claim up to 8000 lumens at 80 watts.

To drive it I bought a cheap Chinese plower supply off ebay for $18.

I cool it with some graphics card heat sink that's been discontinued I bought from Amazon. I mounted it on a piece of sheet aluminum. There's no fan because the heat pipes dissipate up to 70 watts and I only need to dissipate 70% of 55 or about 40 watts. The LED is still a little warmer than ambient temperature but I can put my finger on the aluminum next to the LED and hold it for a few moments.

It's been a lot of fun trying out this technology and there's no question it's the light of the future with rapid advances. My total cost was about $55.

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very cool..im doing my due diligence investigating
LEDs..for my indoor gardening..
right now im using T5 ho lights..i am pleased..but my
light bill is going up..:( i like that LED lighting also has
available spectrum light as i would require..im looking for
more blue spectrum for vegetative growth..not flowering/fruiting light..
and i like the significant less energy use by leds..
hope to see more postings..good luck to ya !!!

    Bookmark   November 17, 2013 at 5:48PM
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"more blue spectrum for vegetative growth..not flowering/fruiting light"

That seems to be what many people think although you can read many studies that don't support that thesis.

"experiments at Kennedy Space Center have reported greater growth and stem elongation for plants grown in the presence of HPS lamps when compared to plants grown under more blue-rich lighting sources." -from usra.edu

Today, nothing provides better yield and efficacy than HPS.

Poke around http://www.ledgrowlightforum.com and you'll find disappointing results compared to HPS.

LED is the future but today it's not a panacea for increased light bills.

    Bookmark   November 17, 2013 at 7:45PM
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may be steve.but for most of us.. HPS would burn our homes down..eeekk.. so..im avoiding them.
as for elongation..theres a balance..of course..
seems a balance of light spectrum is important..not reading much uptake of the green spectrum..

    Bookmark   November 17, 2013 at 8:16PM
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