Topic: LED growlights

[chriscross1966]

Has anyone ever used them?... Specifically for alliums in my case and not this year but probably next year I will have the space/time/etc to have a go at real monsters.... don't like the idea of using HPS or MH growlights cos they're so inefficient.... plants only absorb red and a bit of blue .....

chrisc

[Chrispy]

I'm also interested, so bump.

There was a bit of a thread a little while ago on grow lamps in general.
http://www.allotments4all.co.uk/smf/index.php/topic,56846.msg579308.html#msg579308

I'm off to ebay, see what they say on there.

[Vinlander]

LEDs will be  absolutely brilliant  ;) when they are a bit cheaper, but at the moment they are very expensive to buy per watt and even per lumen compared to efficient fluorescents* - and LEDs are only somewhere between 30 and 90% more efficient than fluorescents.

If you want red and blue light at high efficiency then an aquarium growlight is a lot cheaper to buy and very nearly as cheap to run.

* at the moment you'd need at least 2 x 5W LED to match a 20W fluorescent - even mass market white ones will cost £20-25 each. Specialist magenta mixes are bound to be more expensive (to buy - not to make) whereas a 20W aquarium growlight can be picked up for £10-20.

Since a household 20W compact fluorescent costs £1 from the right place then you could run 2 instead of 2 x 5W LEDs for several years on what you save - and I reckon your plants will prefer getting twice as much white (even if some of it's green). Even better if you are using them under glass in winter - the small amount of 'waste' heat isn't wasted.

LEDs will get cheaper - in a way it's a pity we have so many CFBs so the real pressure is already off our bills - we need someone to buy lots of big LEDs before the price comes down.

[chriscross1966]

I work for a company that uses lots of LED's.... we get 20+ lumens out of 5mm LED's without a problem, tune the colour for chlorophyll and surely the efficiency should make everything else look silly?

chrisc

[Vinlander]

I work for a company that uses lots of LED's.... we get 20+ lumens out of 5mm LED's without a problem, tune the colour for chlorophyll and surely the efficiency should make everything else look silly?

chrisc

Hi Chrisc,

What kind of wattage are you using? Are they raw LEDs (cheap)? - overrunning them? or the ones with an integral 250v PSU (expensive)?

LEDs are really good, and I can't wait for them to become cheap... but any theoretical efficiency figure that makes LEDs look more than double the (already high) efficiency of fluorescents is either ignoring the PSU losses, or looking at old figures for fluorescents, or speculating about OLEDs - or a mix of these.

5mm LEDs are very cheap but you need a lot of them to match the 1000 lumen output of a £1 compact fluorescent. When you cluster 50 x 5mm LEDS running flat out you tend to start cooking the ones in the middle.

Tuning for chlorophyll is easy - you look at the leaf, and the colours you see are the ones it isn't using. It's true that there is a lot of green coming out of a white fluorescent - that's why magenta growlights were invented, but even the white ones have a big blue spectral peak and those photons are much better at splitting CO2 - so it's not as bad as it seems.

Cheers.

[chriscross1966]

We use them in strobes for motion capture systems... about 200 in the big arrays and because they're pulsed we overdrive them like crazy... but it means we're always playing with HE LED's....

Looking at the stuff online I'm guessing that the problem for vegetable growers is the blue light element.... lets faceit most of the "growth" in growlights is down to people growing illegal plants.... I'm interested in onions and I want to boost early green growth in dark winter months as an augmentation of natural light... very different to the illegal boys who want maximal early fruiting....

Finding the various reports and also looking at the various performance characteristics of the LED's and the absorption spectra, I'm guessing they're having problems hitting the the lower peaks, they're more violet than blue and the efficiency of violet is a chunk lower.....hmm....

if I get a chance I';ll have to have a play with this stuff.... I've got spare LED driving kit lying around at work and small PSU's aren't hard to get hold of.... Will need to be done against controls....

The other big thing with LED's is that they can almost touch the plant without scorching it..... highly efficient transfer of energy.....

chrisc

[robbo]

WOW. A bit over my head that lot I am afraid. Can I pick the brains of you lighting experts please? I have set up a propagation area in my bedroom (attic bedroom),it comprises of a wooden frame 6ft x 5ft x 30inches high. The four walls are all aluminium foil and the overhead lighting comprises four blue spectrum fluorescent lights all set on a timer to daylight hours. The only natural light is from two skylights on the north facing slope of the roof. I am using it for my flower seeds and seedlings because my greenhouse is unheated. Is this sufficient or what can I do to improve it, maybe swap two of the blue spectrum lights for red spectrum?

  Robbo.

[Vinlander]

Is this sufficient or what can I do to improve it, maybe swap two of the blue spectrum lights for red spectrum?

  Robbo.

I can't speak for Chriscross in this one but I know more about lighting than I do about how plants respond to it!

In terms of using growlights I probably have less experience than you do - certainly in terms of blue/red balance.

My most intensive setup is a 60x 30cm heated 27C enclosure containing a capillary mat system and I tried a magenta aquarium growlight (20W) one year and replaced it with a cheaper installation of more power using compact fluorescent lamps (2 x 20W).

I mainly tried to bring on newly germinated tomato, pepper and aubergine seedlings and found the higher power a bit better but neither lamp system was really enough for the temp.

The toms still got too leggy, peppers and aubergines looked good but a bit slow - I probably didn't give enough fertiliser.

Sunlight is such a shedload of lumens! Even in Winter...

[chriscross1966]

Sunlight is such a shedload of lumens! Even in Winter...

Too true.... that's why I'm thinking LED, it's thermally efficient per lumen as well as electrically... and onions won't want too much heat.....

chrisc

[w00dy]

Ive been growing onions this year with an 300mm*300mm LED light board, so far so good they look like nice healthy plants, becuase there is no heat its easier to control this part of the equation and there is no worry about bolting.  My only concern is that they have not yet developed any true leaves and they have been planted since new year, im attributing this to the low temperatures as they are in my lean-to and have been getting an average temp of about 5 degrees which im aware is a little low for the onions.  We have a payment meter for our electricity, and my missus has not once said anything about the usage and trust me if she was feeding more cash into our meter she would let me know about it.

Ps The board im using has equal numbers of red and blue leds for vegative growth and fruiting.

[BarriedaleNick]

Personally I would go for a 125w or 250w CFL for getting an early start on certain plants.  Blue bulb for growth.  Admittidly these are aimed at "cough" certain growers but they run cool and seem to have a decent spectrum..
http://www.greenshorticulture.co.uk/CFL-Lights-95/CFL-Grow-Lights-122/Budget-125W-CFL-Systems-560.asp

I wouldn't bother with LEDs at the moment - too expensive per lumen - give it a few years

[w00dy]

Was telling lies earlier, i noticed after posting that one of my onions does indeed have its 1st true leaf forming.

[Vinlander]

Personally I would go for a 125w or 250w CFL for getting an early start on certain plants.  Blue bulb for growth.  Admittidly these are aimed at "cough" certain growers but they run cool and seem to have a decent spectrum..
http://www.greenshorticulture.co.uk/CFL-Lights-95/CFL-Grow-Lights-122/Budget-125W-CFL-Systems-560.asp

I wouldn't bother with LEDs at the moment - too expensive per lumen - give it a few years

Are the big professional CFLs really any different? They look like the same tube but 5 times as long.

I25W worth made from 7 x 20W cool whites would cost £7.

How does that compare with the cost of a 125W single?

Do you think the reduced 'wasted' green light makes it worth going for professional kit?

Cheers.

PS. Yes CFL/CFBs are fairly cool. LEDs may emit as little as half the waste heat but it's still there. I wonder if having 5mm of clear plastic between your finger and the active zone has a bigger impact on perception than the actual efficiency...

[BarriedaleNick]

Interesting question Vinlander...

Cool whites are rated at 4000K (ish) whereas the "pro" lamps are 6400K - though there are no standards for this.  Technically you may get more light in the right end of the spectrum but whether it makes much odds is another question. I guess for keeping a few seedlings going then the cheaper option would suffice.

Can you get  20W cool whites for £1 each?? Excellent price if you can.

[Vinlander]

Can you get  20W cool whites for £1 each?? Excellent price if you can.

I bought a load for that price when they were trying to jog the UK public out of their inertia in the face of the unfamiliar. Even Dyas were selling them at that price.

I like bright rooms so I replaced every old 40W and 60W with a 20W CFL and put in the odd 25W or 30W to replace old 100W bulbs - but the big ones are expensive - would have been cheaper to add an extra fitting.

I'd rather halve my bill and use the rest of the efficiency gain to make the place brighter. The waste heat doesn't bother me in winter - in fact our gas bill has probably got slightly bigger since we got rid of the incandescents.

I'm a bit dismayed that the 25s and 30s still haven't come down in price - people haven't stopped  grumbling about how a 20W CFL doesn't quite have the oomph of an old 100W - so why don't the big stores sell the bigger sizes?

Checking the web, 20W ones are still available from Screwfix at £1.79, so they are probably available in the high street at £1.50-1.80. Keep an eye open for special offers.

Cheers.

[campanula]

hmmm, in agreement with barriedale Nick here - you could put an array of 20watt CFLs on a board and maybe propagate a few seedlings but you couldn't grow on a plant under these. Am also waiting eagerly for LEDs to come down in price though.
cheers, suzy

[Vinlander]

I've been using ordinary CFLs for 2 years and they will definitely bring on seedlings until it's warm enough to put them on a shelf in an unheated greenhouse. Especially peppers and aubergines which don't seem so desperate to go leggy as toms are (the toms soon recover).

Wilco have a special offer of 23W CFLs @ 97p each. Equivalent to 120W incandescent but won't scorch the plants.

Not cool white type but the plants can still use the red end.

They are GE ones which have an instant start-up (not that it matters to a plant).

This is by far the cheapest way to bring stuff on. Chuck a blanket over the enclosure at night to avoid annoying the neighbours. At one per standard tray in any kind of enclosure the 23W will bring the temp around 20C at night - perfect!

Basically you pay for the same heat as a propagator but the light comes free.

Even better is to run a little ex-equipment 12V fan in there - air movement reduces fungi, evens out temps, improves stockiness by stressing the stems a little.

Don't use a mains fan unless it's fully tropicalised.

Cheers.