LED lighting.

[Dorsetman]

Very technical, but maybe someone has some answers ?

LED lights. They are the latest thing, and have the remarkable advantages of low electricity usage and very long life.

I became aware of them when I saw my new car and checked things out. Then I bought three for my bathroom (lamps, not cars ! ) - a brighter light for shaving by replacing three 20 watt halogen bulbs ( life usually less than 1 year) with three 1.8 watt LEDs - life , said to be good for 30,000 hours of usage .
I reckon my bathroom lights are on for an hour a day, total. They should be good for 85 years or so . I am not Methusalah...but this eases worries about getting value from equipment before it wears out.

So that started me thinking about the lamps in my greenhouse, especially since LEDs are available in a range of specific colours for horticultural use. One lamp assembly has 1% emitting infra-red only, another percentage emitting at the red end of the spectrum ( all this for vegetative growth, and another percentage at the blue end, for flower production. Fantastic - especially if the running cost can be 10% of what it is now .
Then the problems start. With the conventional metal ballast sun lamps ( blue, red , or mixed spectrum - all of which look white to the naked eye, but warm white, cool white, etc. the lamp output is quoted in lumens ; 1 lumen = 1 foot candle = 10.74 Lux . And I know what lux I want on my leaves, I have measured it with a lux-meter on orchids in the wild.

One dealer said that frankly, you just have to experiment a bit. So I bought a couple of cheap 1 ft square mixed colours “growlight” panels. But after doing some experiments, I reckon my Lux meter is useless for determining the height above the plants to locate them, and also making guesses about how many lamps I need for a specific bench area ( they don’t seem to use lenses or reflectors btw ).

LEDs are not rated in Lumens. Instead they use quite unfamiliar units represented by acronyms such as PAR. One trail I followed up ended with an equivalence quote in mols - molecular weights...another dealer said he could give me umol figures, and when I pressed , he was clearly trying ( successfully) to blind me with science , but I gathered that he didn‘t understand it either.

So, HELP. Has anyone any experience ?

[Mararda]

I do not know much about lights in regards to plants, however I do know that 'mols,' is used as a measurement of concentration in chemistry, so it sounds as if the dealer may have been confusing your query with a chemical reaction...and if he was referring to 'micro'-moles he may have been trying to discern the concentration of an unknown solution using a spectrometer. , which seems bizarre in relation to plants... I am interested in the answers to this post though, as I want to seek an efficient grow light for my window sill Vandas to give better blooms in the summer. (I have achieved blooms, but they are not up to the plant's potential).

[raybark]

This can be a huge thread, but I'll start with the PAR issue - as far as i can.

PAR, or Photosynthetically Active Radiation, is the amount of light between 400 and 700 nm wavelegth that hits the plant per unit area per unit time. That quantity does, indeed, use the mathematical quantity of moles (1 mole being Avogadro's number, or 6.02 x 10E23, units). PAR is measured in micromoles of photons hitting a square meter per second.

Think of it as an estimation of energy transfer - a photon being a packet of energy that is transferred to the plant, so the volume per unit time matters.

Actually, Mr. Dorset, it's red for flowering and blue for growing, not the opposite. I had an issue with that early on too - blue being the more energetic photon, therefore transferring the most energy, which seemed logical for flowering, to me.

[cakedaddy]

I'm interested to learn more about LED as well. I read alot on an aquatic gardening forum. LEDs are very popular for that application and apparently do a good job at growing plants.
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[Mararda]

This can be a huge thread, but I'll start with the PAR issue - as far as i can.

PAR, or Photosynthetically Active Radiation, is the amount of light between 400 and 700 nm wavelegth that hits the plant per unit area per unit time. That quantity does, indeed, use the mathematical quantity of moles (1 mole being Avogadro's number, or 6.02 x 10E23, units). PAR is measured in micromoles of photons hitting a square meter per second.

Think of it as an estimation of energy transfer - a photon being a packet of energy that is transferred to the plant, so the volume per unit time matters.

Actually, Mr. Dorset, it's red for flowering and blue for growing, not the opposite. I had an issue with that early on too - blue being the more energetic photon, therefore transferring the most energy, which seemed logical for flowering, to me.

Hi Ray,

Thank you for the explanation. That is very informative - I feel a bit ashamed that I did not know about PAR until now to be honest. How would one measure it? For example if I wanted to measure the amount of light my window sill Vandas receive at a specific time of day? Would one measure the luminosity and irradiance first? (I have used a lux meter in a museum before to determine the varying luminosity in display cases - voluntary work).

Regards,
Kate.

[raybark]

My understanding is that a specifically-made PAR meter is needed, as most other light meters have filters in them that cut off the measured spectrum, narrowing the range - the human eye us far more sensitive to the middle of the spectrum, so why bother with the ends of the visible range (even though that's what plants use most). I have known of folks disassembling their meters and removing those filters, but I don't know enough about that to try risking a meter investment.

I think another thing to keep in mind that while a lux or f-c meter is a device intended for instantaneous measurement of the light level, a PAR meter is intended to give an indication of the sum of photon flux over a period of time - often that's a daily integral.

Seems to me that if you REALLY want to get technical about the lighting, you need a spectrometer, so you know what specific wavelengths are reaching the plant, and a PAR meter to know how many photons.

<editorial comment>
It's funny. I have been growing orchids for over 40 years, and being a scientist and engineer, like to put as much science into it as I can, yet I have never found much utility in light meters.

When you grow in a greenhouse, as I do, you're pretty much at the whim of Mother Nature for maximum levels, so all you can really control is shade, and it seems fairly easy to determine what's too much or too little by eye immediately, then be observant of your plants and make adjustments as needed.

When I grew exclusively under lights, where a meter seems more applicable to me, I merely (in retrospect) let the sensitivity of my eye to the middle of the spectrum guide me as to "what's too bright" and raised the lamps. Then - again using observation of the plants as my guide - made distance adjustments from there.
</editorial comment>

[Brutal_Dreamer]

Great thread on LED lighting. I've recently invested in a LED light panel for my 55 gallon plant aquarium. It has a blue setting designed for growing the plants and creates a beautiful underwater nighttime effect in the tank. Since moving to the LED panel (about 300.00 dollars), my tank plants have really done well but - so has the algae. It is a constant battle. Currently there is another break-out of what I call string algae. It looks like tiny strings and surrounds everything in the tank. It is pretty easy to vacuum and scoop out, but comes back about once a month. The LED lights are very bright and with the built in timer, perfect for my underwater plants. I could see using the panel as an additional light source for orchids grown indoors. I wonder if it is bright enough to be used alone though?

cheers,
BD

[BigSteve]

From the reading i have been doing it would seem that the LED lights are used as supplemental lights but this is with commercial growers.
Price seems prohibitive compared to HPS/MH but you could save in energy bills.
If i had descent winter temps then i might be tempted to try LED but with the winter temps in UK the heat given off by HPS system saves me from heating my grow room , with LED i would probably have to heat the room as well , which would decrease any savings in energy bills.
As a comparison i had a look at some 600w LED panels , these are 4 to 5 times what i paid for my HPS setup.

[Magnus A]

A little more than one year ago I cared shit of all poeple on the interenet who said that LED was no good an useless for orchids. There were a huge trashtalk on several forum from a few very loud persons.

I have grown orchids in one of my cabinet with only LED light for a little more than one year now. NO other light what so ever! I have had Lepanthes telipogoniflora and calodictyon flowering continiously AND trippled in size. Last week I found a bud on one of my Dendrobium cuthbertsonii. The cabinet stands in my apartment living room without cooling.

[78Terp]

Here in Colorado USA, there is another plant that has just become legal in the State, although still illegal, by the Feds, and the growers of it are using more LED lighting each year as I understand it. Again they could be applied in that environment as supplemental, but they are still on the secretive side of things. So I can't say for certain.