LED Lights

[keto]

Here you go.

Viherpeukku

Sorry, the site in Finnish, but I'm sure you get the idea...

[greenpassion]

I read a few posts here about LED lighting not being very good. I am curious. I have bought 2 chip tec led bulbs from Orchid Limited, and after reading about them and watching the videos, it seems to me that they're maybe better than what I've read. For one thing, in my case, my small collection of orchids aren't tucked away in a 'growing' room, where unsightly light set ups aren't seen. They are out in my living area under track lighting that divides my kitchen and living room) and the cold white light from the T5 lights is unpleasant. The chip tec bulbs give off almost no heat at all, not nearly as much as the 'grow bulbs' (which are incandescent I think) and the light, although not at all bright, is such that I get sharp shadow over the plants. I read from one of these posts that although the light LOOKS dim, it's more than sufficient for the orchids. The jury is still out, and could be for me as none of my orchids are even putting out spikes yet. But, I have lots and lots of very healthy roots growing and new leaves as well.

[greenpassion]

If Led light is so useless, how can companies sell them as grow lights? Orchid Limited sells them and I thought of them as fairly reputable, no??

[Ocelaris]

Originally Posted by greenpassion

I read a few posts here about LED lighting not being very good. I am curious. I have bought 2 chip tec led bulbs from Orchid Limited, and after reading about them and watching the videos, it seems to me that they're maybe better than what I've read. For one thing, in my case, my small collection of orchids aren't tucked away in a 'growing' room, where unsightly light set ups aren't seen. They are out in my living area under track lighting that divides my kitchen and living room) and the cold white light from the T5 lights is unpleasant. The chip tec bulbs give off almost no heat at all, not nearly as much as the 'grow bulbs' (which are incandescent I think) and the light, although not at all bright, is such that I get sharp shadow over the plants. I read from one of these posts that although the light LOOKS dim, it's more than sufficient for the orchids. The jury is still out, and could be for me as none of my orchids are even putting out spikes yet. But, I have lots and lots of very healthy roots growing and new leaves as well.

"Cold" is relative, LEDs aren't warmer or colder than any other form of lighting, incandescent, HID, or fluorescent... you can change the color (except for incandescent) based on the chemicals.

LEDs still are not as efficient as Fluorescents or HIDs, they DO put out MORE heat per lumen than other forms of lighting. Your confusion about them not putting alot of heat is that they aren't putting out much light!

LEDs do have some benefits, on/off speed, longevity. But they do not excel in efficiency or color output (i.e. they are only one color, and you can skew the blue ones to put out other colors to make white).

Unless you're measuring your lumens with a light meter, and are aware of the Color Rendering Index, and Correlated Color Temperature, everything is speculation. Numbers don't lie, but plants are fairly forgiving when you give them a "white" light, so the LED lights may do fine, are they more energy efficient than other forms of lighting? Maybe not, but if they last 10x as long, maybe that's an investment. Just don't think it's magic, they are still subject to all the same measurements as any other source of lighting.

[DavidCampen]

Current LEDs are not more efficient than fluorescent of HID (High Pressure Sodium or Metal Halide). It can be a bit hard to compare though since all of these lights tend to be rated in lumens. The lumen metric is weighted to show equal perceived brightness to the human eye but what works best for the human eye and what works best for plants are two different things. The human eye is most sensitive to green light at 555 nm and is much less sensitive to red and blue whereas in a plant green light tends to be reflected (and thus not used) while red and blue light get absorbed by the plant and used for photosynthesis.

There are a couple of advantages to using LEDs:

LEDs are can be used to produce only the red and blue colors that are most efficiently absorbed by plants without wasting any power in producing green light that will likely not be absorbed by the plant.

If you are not growing a vast sea of plants then LEDs can be used to give highly directional light that can be directed to exactly where it is needed.

These two properties of LEDs are attractive to me as I have plants in clusters, here and there in a garden room and I would like to place the lights high up so as to not interfere with air circulation and the esthetics of the room. Also the room has natural light which I don't want to block. LED lights can be made small and higly directional so I will be able to place small form factor LED lights high up up on the ridgeline of the room where they will not be seen or interfere with air circulation or esthetics. I also plan to use red emitting leds so that I will not be wasting any power on producing green light, since the room also has natural daylight and incandescent illumination then the pure red of the LEDs will not be a bother.

But if you are trying to grow a vast sea of plants that cover most of the floor space of a room then t-8 fluorescent or high pressure sodium lights will be more efficient than white LEDs. Perhaps pure red and blue LEDs would be about as efficient as fluorescent or HPS but current LEDs are also vastly more expensive.

[DavidCampen]

For the highly directional, pure red LED spotlights that I want, at the moment it looks like I will have to build my own.

This company has products that I like:
LedEngin
If they were available in pure red then I might use one of their assembled lighting products:
LedEngin
But since they don't offer their higher power lamps in the tight 12 degree spotlight configuration and they don't offer any lamps in pure red I will likely construct my own spotlights. As a light source I will probably use their "10 watt" LZ4-40R100 emitters that produce 625 nm red light:
LedEngin

[greenpassion]

Thanks for the replies. What I don't like about the red and blue led bulbs is that it'd look like a disco in my living room. Orchid Limited says that the new chip tec bulbs and the others, the 38 diode, 60 diode and an 80 diode are a very bright white light that works well for lighting 3 to 5ft above the plants. I would never use the colored lights unless I was growing them in a back room or someplace other than my living area. I only have 5 orchids and they are a focal point in the room. So....

[Ocelaris]

Originally Posted by greenpassion

Thanks for the replies. What I don't like about the red and blue led bulbs is that it'd look like a disco in my living room. Orchid Limited says that the new chip tec bulbs and the others, the 38 diode, 60 diode and an 80 diode are a very bright white light that works well for lighting 3 to 5ft above the plants. I would never use the colored lights unless I was growing them in a back room or someplace other than my living area. I only have 5 orchids and they are a focal point in the room. So....

I think David has some good points, I'm a bit biased, so his is probably the most reasoned arguements.

Unfortunately, regardless of which lighting technology you use, NO light is immune to the way light decreases exponentially away from a source.

I did some calculations a while back, but basically, if you start out with a 8,000 lumen bulb (about a 300w light bulb) at 0 feet you get 12,000 Foot Candles, but you drop to 200 FC at only a foot and a half away!

In other words, your lights at 3-5 feet away from the plants are like dishes of water with pebbles to increase humidity... unfortunately probably not making good use of the expensive LEDs.

I used to have dual 400watt metal halide bulbs at at 4 feet away I could grow phalenopsis reasonably well. If I had just 2 fluorescent tubes using 80 watts sitting a foot away it would probably have been more useable energy to the plant, and only 10% of the power use!

100w MH (8,000 lumens)
feet ----- Foot Candles
0 ----- 12,500
.5 ----- 2500
1 ----- 850
1.5 ----- 200

http://www.orchidboard.com/community...ht-levels.html

[DavidCampen]

Actually, a light source radiating equally in all directions (e.g. a sphere) has the light intensity decreasing as the square of the distance which is an algebraic function not an exponential function so, to be a bit pedantic, you should say that the light intensity decreases algebraically.

But this decrease in intensity as the square of the distance only applies to sources that are radiating equally in all directions. A laser is a good example of a light source that does _not_ radiate equally in all directions and so its intensity decreases only slowly with distance. A fluorescent or HID light source can be partially enclosed with a reflector so that the light intensity decreases as less than the square of the distance but because HID and fluorescent lamps are relatively largeit is difficult to make a really good collimating reflector. LED light is much more a point source and so it is easy to make a small relector that will highly collimate the LED light so that it does not spread out with distance.

Here is a datasheet for an LED reflector that produces an output with only a 12 degree divergence.
http://www.ledengin.com/files/produc...LNS-1T06-H.pdf