More on LEDs

[Shiva]

I'm thinking of moving completely to 3 watts leds next spring in my plant room. The red and blue are very expansive, $500 plus shipping, for a 450 watts panel (which consumes really 300 watts) and I will need six of them to cover the whole area. I will keep my two 250 watts rated CFL lamps to check on the plants for new growths, new spikes, and possible diseases. These will be turned on and off as required.
The first panels to come out years ago had 225 leds for 16 watts of power. They didn't work that good and, mostly, the quality of fabrication was awful.
One problem I have is figuring out which panels are best because of the claims and counterclaims by various sellers. It's very hard to understand all the linguo. For instance, Ray's chip lights he's selling are rated at 13 watts for 64 leds. My old panels have 225 leds for 16 watts. And then, there's the area that is covered and how high they have to be above the plants.
Anybody can shed some ''light'' on all this?
Thanks!

 

[aquacorps]

Great questions

 

[Ray]

My VERY limited knowledge of LEDs is that 1) they're not all created equal, and 2) more current = brighter, as long as the chip can handle it, which includes significant heat dissipation.

 

[littlefrog]

I can probably (probably? I need to know what you are considering already) do better than that on the bigger panels. I have 300W and 600W configurations from my supplier... I'm using a 300W now. Can't say I've ever sold one (most people go for smaller units) so I don't have my cost in my head, but I don't mind passing on a really good price to orchid growers. PM me.

300W LED is probably similar to ~600W metal halide in terms of coverage area. I have not used the 600W panels. It seemed a bit excessive for my needs. I don't think it is something that most orchid people would use, unless you have a really high ceiling.

I don't know your space requirements, but shoot me a PM with some specs and I can try to work up something for you based on my experience. More than half of my lighted space is with LEDs, and I'm growing 'commercial' scale. About half orchids, half miscellaneous tropical stuff (bromeliads, ferns, etc).

 

[Shiva]

My VERY limited knowledge of LEDs is that 1) they're not all created equal, and 2) more current = brighter, as long as the chip can handle it, which includes significant heat dissipation.

Heat is indeed another concern I have. How do LED panels compare to the heat of a 400 Watts HPS and ballast?

I have yet to see a vendor put that figure up. The LEDs are evolving so quickly that it has become nearly impossible to get all the right information. So far as I can tell now, the only way you can make comparisons is to try them. Good thing I like experimenting.

 

[Ray]

I can tell you that my bulbs are enclosed in a ribbed aluminum case that is both the enclosure for the rectifier, resistors and circuit board, as well as heat sink. They are very warm to the touch, but not "burn yourself" hot. 3" below the LEDs, you can detect no temperature increase. They are very cool compared to HPS.

I cannot speak for the ballast, but I don't think you dare get near an HPS bulb.

 

[Shiva]

The led panels come with cooling fans for the bulbs. So I assume that they must produce some heat. My guess is that even then, they probably don't come close to a 400 Watts HPS, let alone a 1000 one. Winter won't be a problem as I have to heat the room anyway, but since I have to cool down the room in the heat of summer, I'd prefer not to heat and cool it at the same time.

 

[littlefrog]

I don't run the 300W panel in the summer, since those plants are outside. But the heat is far far less than a 400W MH or HPS. You can touch these, and indeed hold your hand on them for some period of time. I've never measured the temperature, but definitely cooler.

 

[Shiva]

I'm glad to hear there's no heat problem. Thanks!
As an aside note, what strenght of panel would you recommend to light the area covered by four T8 fluorescents 48 inches long?

 

[littlefrog]

For what I have experience with, I'd recommend two 28W panels.

I've also been playing with a new LED light strip that would replace the T8's directly. They are 44" long, waterproof, and bright as heck. Three strips would replace the 4 tubes, easy. Could even mount them in the same fixture. I have those in white, and had some made in blue and red (blue and red are in different strips, for technical reasons).

Honestly though, if money is an issue, I'd replace the four t8 tubes with a two tube t5 fixture. Nothing wrong with fluorescents in most situations. I think these LEDs would be great in wet environments (fish tanks) or in growing truely cool or intermediate plants - I don't think I'm going to find anything better for growing pleurothallids than the LED strips, at least in white.

 

[keithrs]

Going on the cool terrarium theme... Do you have to have red and blue LED if you have white? Also how much penetration would you say LEDs get compared to T-5?

 

[littlefrog]

No. Red and blue light have differing effects on growth and flowering. It is generally believed that red light enhances flowering, blue light enhances vegetative growth. This is probably overly simplistic. White light (if it is 'true' white light - or something close) has both red and blue in it, as well as some wavelengths that plants don't really use (green) and some that are a bit more ambiguous as to their function. It seems that plants do pretty well with just red and blue, but there are cases where more wavelengths increase results.

When you see a 'red/blue' style grow light (I call them alien abduction lights), there is generally some ratio of red to blue. Most of the ones I use are about 2:1 red to blue. But I've seen 8:1 red to blue offered. Rarely do I see lights which have more blue than red.

So, for a terrarium (or vivarium), white light is probably best because you are going to be observing your plants (and/or animals) under that light. Other colors will weird you out. Unless you have them on separate switches (turn on white for viewing, color for plant growth).

Where the red and blue come in handy is for propagation or flowering. In theory (and I'm going to test it for orchids, really, someday) growing seedlings under blue light will give you compact growth with no unnecessary diversions into flowering. We all know some plants bloom too young... Then, switch to high red when the plants are of good size, and watch your blooms go boom. For general growth and flowering at the same time, then mix a couple reds with a blue. That part I know works, I get both good growth and flowering of adult plants under LEDs, I'm confident in that.

Penetration is generally a lot better with the LEDs, since they are directional and (often) focused with lenses. Even if not focused, you still get more penetration because all of the light is going in the same general direction. With a fluorescent tube, half of your light is going up, and bouncing back down if you have a reflector (possibly through the tube), you lose a lot of light that way. Without a reflector... well...

 

[keithrs]

If LEDs are more focused, Is the light spread more narrow then on T-5's?

 

[littlefrog]

If LEDs are more focused, Is the light spread more narrow then on T-5's?

That is a pretty safe assumption. As a practical example, I light a 30" wide bench with a single t-5. Seriously! It works, I didn't think it would either, but I'm not growing high light plants under it (mostly foliage and ferns). I don't think I could do the same with a single LED strip. I'd want to use two to light the same area. At that point the cost/benefit analysis gets pretty hard to justify, other than the intrinsic neatness of LEDs (and the cooler operating temperature).

 

[Ray]

Look at the geometry of the emitter. A bare T5 tube radiates uniformly in all directions. Throw a reflector on it and the light that is otherwise lost (to the plants) can be redirected to them. The design of that reflector and the bulbs position within it determines the spread. A truly parabolic reflector with the tube in its focus will direct the light narrowly out of the parabola, in a width equal to its opening.

"Naked" LED chips emit light in a patter that is almost hemispherical, so if you had a line of them, like those strip Rob has mentioned, it's more-or-less equivalent to a half of a T5, in terms of light pattern. Having a reflector around it will still trap those photons that have the audacity to escape to the sides, rather than down, and reflect them onward.

Add focusing lenses to them, and you preclude the need for a reflector.

 

[Susie11]

I have just got into supplemental lighting and I am looking for some advice about the bulb that I have just bought. I got my first Dendrobium -a spectabile- the other day and as it is a light hog and as I live in the rainy UK I decided to get a bulb. I have gone for a 11w 5000k daylight bulb. Is this going to be enough to get this Den to grow and flower? Thanks in advance.

 

[cnycharles]

Hello Susie,
Your post may have gotten lost on the end of this thread. An 11w bulb sounds somewhat dim; is this a spotlight? Dendrobiums, bless their souls since most of them die in my care, like the one you mention need a lot of light. If you are adding this bulb on top of sunlight from a window or in a greenhouse, and you are leaving the bulb on for a long day length, then that might be enough. If it's the only light then I wouldn't think it would be enough

 

[Susie11]

Hello Susie,
Your post may have gotten lost on the end of this thread. An 11w bulb sounds somewhat dim; is this a spotlight? Dendrobiums, bless their souls since most of them die in my care, like the one you mention need a lot of light. If you are adding this bulb on top of sunlight from a window or in a greenhouse, and you are leaving the bulb on for a long day length, then that might be enough. If it's the only light then I wouldn't think it would be enough

Yes someone else said that 11w was too little so I am getting an 60w daylight bulb instead. I am growing in a normal room with a lot of natural daylight flooding through the window but even so I still want to make sure that this beauty blooms for me soon. I think that 60w 6500k should do the trick?
Thanks for replying Cyncharles.

 

[cnycharles]

if you aren't sure if added lights will be intense enough, adding more time that there is light can help 'add up' your total light. by having a timer or putting yourself on a schedule so that you turn on the light early in the morning and then turn it off later in the evening, the plant will collect the extra light over time. it's the total light in this case; adding medium light for a long time will hopefully equal 'bright' or intense light over a short time

you'll still have to fulfill the plants desire for whatever day/night temperature changes, or warmth during the day

 

[Shiva]

What kind of light are we talking about?