If it puts out enough light then its good for growing. If you had to pick a spectrum for growing plants then HPS is about the last thing you would pick, but everyone uses them because they put out so much light. White light LEDs are unlikely to have a much worse spectrum for growing than HPS, probably it will be comparable to a cool white fluorescent. The spectrum of the existing white Luxeons is quite similar to halophosphate fluorescents with a narrow blue peak and a broad peak from green to red, a little nearer the green than the halophosphate but without the added green spike. The only remaining issue is getting hold of a couple of hundred of them :)

True, but I like the idea of putting a few of them together to light a small focused area as a display light... Thinking of cutting a "window" on my living room wall and installing something like a pot light to display my blooming orchids, but then, CFL's don't focus very well, and the reflector type hologen lights produce more heat to fry my plants than growing them!

Some of my phal. blooms last up to 3 month so having something that can keep them healthy matters! LED lighting just came to mind... Now if only they provide CRI info!

With high power LEDs, one of the problems has always been the need for expensive heatsink provisions.

The other expensive thing is the need for sophicticated electronic driver electronics in the power supply.

Regarding focusing spot light, a 100 watt MH bulb can give you a highly tight spot throw without lots of heat with the right reflector.

dcarch

LEDs are great for "accent" lighting. The white light LED manufacturers are getting better about publishing CRI data with their products. White LEDs are now available in more or less the same ranges as fluorescents, from pretty awful up to 90+. For example, the standard white Luxeon III has a CRI of 70 and colour of 5500K, but there is a version with colour 3300K and CRI of 90 (they pretty much just took out the big blue spike and left the nice wide green/orange band). Unfortunately the higher CRI comes at a price: only about a third as bright. You obviously won't see CRI data for the single-wavelength LEDs, it would be close to zero. Cost is about $5 for the 1.2W Luxeon III in quantity, giving 70 lumens in the most efficient version.

"LEDs are great for "accent" lighting."
Agree. Watch out for different distrubution characteristics for hi power LEDs. custom Lenses and reflectors may be required for desired throw.

dcarch

Thanks for the input!

>Regarding focusing spot light, a 100 watt MH bulb can give you a highly tight spot throw without lots of heat with the right reflector.

For a single plant that occupies 1 sqft and requires medium light, 100 W is a bit of overkill... My energy bills are already hight enough without that... I was thinking somewhere along the line of about 20 W or less... at this low amount, heat shouldn't pose much of a problem... As for power, I figure on just using an old notebook computer power adaptor (rated 15V at 3A = 45W max). stick about 5 rows of 4 in series, with a power resistor to obsorb the remaining 1V or so (3.5V*4=14V drop accross the LED's) Throw in a current limiting resistor in parallel with the 5 rows of LED's and the circuit is really not that complicated. Probably stick them all into a piece of breadboard to make changing things easier.

All this is just on paper of course! With a price-tag of around $5/LED, even with 20, that'll be $100 already. That's assuming that they'll even ship such small quantities!

I think they'll be a lot more than that in small quantities at retail. That's if you can get them at all, I'm guessing they'll only be shipped for inclusion in other products at first.

High power LEDs shouldn't just be attached to a power source, they need to be properly heatsinked or they will burn out in a few hours. Even these new super-efficient LEDs still turn over half their input power straight into heat, but LEDs don't radiate any heat so it is all retained in the chip.

Thanks, I'll keep that in mind, and do some more reading!

There is not a lot of light from a 100w MH bulb. You can try 75w if you want. It will help grow the plant, not just spot.

If you must play with LEDs try low power ones. they are very cheap get 50 or 100. They come with narrow beam lenses so you don't have to buy separate lenses which may be required for hi-powered LEDs. Lots of soldering, but it can be done. No heat sink needed if you don't overdrive them.
also, they have warm white LEDs.
dcarch

I have some experiments going on with 100% LED growing. Also am using some high power LEDS in collimators and lenses with good success. I have the LED growing and info documented and photos on my website at www.greenpinelane.com if you are interested. I'm not selling anything, the site is just informational. Check it out if LEDs interest you. I've now grown sweet bell peppers from start to finish with LEDs and the peppers are just about ripe! I have some cucumbers and tomatos going now in early grow stages with updates and photos.

Here is a link that might be useful: greenpinelane