The Truth About LED Lights

Hey Dormgrow,

I am using your 864 watt hood in my 5x9 tent on a light mover. It sucks that you discontinued this immediately after my order because I will be running two tents and wanted to keep them the same. Within the next few weeks, I will be ordering another hood, 900 watts this time. Can I exchange my 2 month old 864 for another 900?

Your website doesn't mention height requirements on any light bigger than 600 watts. I currently have it at 36" from top of canopy and it seems to be working well, but its my first run and I have nothing to compare to. Does the fact that its moving allow me to get closer? What height should I be at? Is this one light sufficient for my space? Also I do have a meter that measures lumens and foot candles (not sure if that applies with LED since its all about spectrum). Can this help me dial in my exact scenario?

Thanks for letting me pick your brain. I look forward to hearing back!
SYN
 
Sorry for the delay in replying. this is my busy season
My origional light was a Hydrioponics Hur 2011 11 band 180W model with 90 W of Veg and 90W of Flower

I've built some new 50w lights using my led muxture and some chips I had made in China. Have plant on 18 hr cycle to get more growth and branching then I'll put into 12 hr to flower will ipdate with photo when it happens, and when I harvest


This is the spectrum of my light vs adsorbtion based on a 60/30/10 ratio of chlrA/ChlB/Beta C. You can see that it is a good match. I also shown is the spectrum of a commercial light;s specifications



 
Not sure what strain you are growing but it looks very leggy and thin stemmed. If you are serious about making a high quality light and getting good spectral data on your light, you should talk to the guys at Avnet Electronics about their Avnet LightLab. They are now open to the public for testing and documentation of data for all aspects of lighting. It covers spectrometer, color rendering index (CRI), optical efficiency, source and system efficacy, total flux output, and thermal analysis and mapping.
 
Yes my ICE plant is leggy. Up till being put under the lights, the plant was raised in a greenhouse. So wait for the next picture in a couple weeks when I start flowering. And I expect that 5-6 weeks after that for the final plant.
 
WillyP said:
I've built some new 50w lights using my led muxture and some chips I had made in China.
Click to expand...

Interesting lights ... they look like bulbs, are the leds clustered together or are they each a single 50 watt LED?

in any case it looks like a lot of light is being lost in the hood?
 
xxxSYNxxx said:
Hey Dormgrow,

I am using your 864 watt hood in my 5x9 tent on a light mover. It sucks that you discontinued this immediately after my order because I will be running two tents and wanted to keep them the same. Within the next few weeks, I will be ordering another hood, 900 watts this time. Can I exchange my 2 month old 864 for another 900?

Your website doesn't mention height requirements on any light bigger than 600 watts. I currently have it at 36" from top of canopy and it seems to be working well, but its my first run and I have nothing to compare to. Does the fact that its moving allow me to get closer? What height should I be at? Is this one light sufficient for my space? Also I do have a meter that measures lumens and foot candles (not sure if that applies with LED since its all about spectrum). Can this help me dial in my exact scenario?

Thanks for letting me pick your brain. I look forward to hearing back!
SYN
Click to expand...



You probably purchased the 864 Watt from our eBay distributor who used this nomenclature. It is actually the same as the G8-900. 288x3Watt diodes is 864 but is also referred to as 900 for simplicity. Same is true for the 432 (144x3Watt) which is referred to as 450.
The height requirement for this light is 36-42inches and with 2 of these lights you will provide adequate coverage for your space. Lumens is a measure of brightness and is used for white light, not LEDs with different wavelengths.

For faster response, email your questions to info@dormgrow.com
Use coupon code GROWLED for additional savings at Hydroponic LED Grow Light | LED Growlights | Dorm Grow
 
DormGrow.com said:
You probably purchased the 864 Watt from our eBay distributor who used this nomenclature. It is actually the same as the G8-900. 288x3Watt diodes is 864 but is also referred to as 900 for simplicity. Same is true for the 432 (144x3Watt) which is referred to as 450.
The height requirement for this light is 36-42inches and with 2 of these lights you will provide adequate coverage for your space. Lumens is a measure of brightness and is used for white light, not LEDs with different wavelengths.

For faster response, email your questions to info@dormgrow.com
Use coupon code GROWLED for additional savings at Hydroponic LED Grow Light | LED Growlights | Dorm Grow
Click to expand...

You're right, I think I did buy it from ebay. I appreciate your answers to my questions and the coupon! I'll buy my next hood from your site soon!
 
This data that I used to define the power requirements for the LEDs in my light. The data is based on a solar flux of 1000 watts/M2 but of this only about 5% is used by plants. One of my 50W lights provides the equivalent solar radiation for 0.3 to 0.4 square meters

Soloar_Radiation_Values1.jpg
 
The truth about LED lights is ... they work
 
Apparently hosebomber, in another thread, gave some definitive
data about this, debunking the 1/3 the power, and thus the 3 grams
per watt. So, the yield we'd be looking for for commercial lights is
1.5 grams per watt.

Is anyone getting that? With whose lights? Note that it's only
with a GOOD light that you'll even get that. LEDs are barely ready
for prime time -- "truth about LEDS" notwithstanding.


- Lenny Gray -


| On 8-18-12, at 10:44 AM,
| Hosebomber wrote:
|
| Re: LED lumens, again
|
| To date no other company has shown the proven results as well
| as Advance IMHO. However there are a few good companies on the
| market. If you see a company claiming 1/3rd the power use of
| a HPS or claiming the light is a 900 and actually draws 387
| (true statement about 1 company) close that browser tab and
| move on to the next. If they are lying about their product
| there is a reason.
|
| IT IS NOT POSSIBLE WITH CURRENT MASS PRODUCED
| MODELS TO GET THE SAME RESULTS AS AN HPS WITH
| ANYTHING LESS THAN 2/3RD THE POWER.
| [emphasis Lenny's]
|
| ie with a very good 400 watt led you could get about the
| same yield as a 600 watt HPS. To get better efficiency than
| that it needs to be a custom panel built for your grow area
| and then 40% power reduction is close to max. I've gotten as
| high as 47% power reduction with almost exactly the same yield
| (within 1 gram of tomatoes) in a hydro setup with light barriers
| and running the same nuits to both sides and light being the
| only variable.
 
re:
"The reason the stated wattage and actual wattage differ is because the stated wattage is the sum of the number of diodes x max wattage per diode, for example 100 diodes x 3watt = 300watts. The actual power draw is always less with LED lights because each diode might draw anywhere from 1.8watts to 3watts depending on the wavelength and the amps of the particular diode."

Though you, SteveHMan may agree, it's not true. A 3 Watt chip will draw different amounts of current, resulting in different power, solely by reason of the circuit design it finds itself embedded in. If you put more voltage across it, it will draw more current. A "constant current" supply varies the voltage until it gets the target current. The "3 Watts" is the maximum a validly-called 3-Watt chip can handle. That will not be the point that gives the maximum life for the chip, nor will it be the point that gives the maximum radiated power per watt of input. It usually will be the point that gives the maximum radiated power -- just not the maximum radiated power per input-watt. Thus, the test point for a 1-Watt diode is generally 350 ma at 2.2 volts, for a power level of 0.77 Watts. Similarly, a 3-Watt diode will often be run at 2 watts for its maximum efficiency. These are both the best "lumens per watt" for that diode. Note, I say "lumens per watt" as an engineer who knows what he is talking about because I'm not talking about comparing apples and oranges. The comparison of lumens is one way of specifying radiated power, and is a thing that people understand, even when not thinking about white light. In fact, a white light will only show between 37% and 43% of the lumens that a 555nm monochromatic green will show. Human eye sensitivity responds to the green most. 660nm Far Red and 440nm Blue will only count as 5% of the lumens and are thus the "apples" that I would never compare to any "orange". But "more lumens of a specific color" is more radiated power.

If more people learned the language, we'd see less attempts to sell "so much yield", and more admission that getting 1 gram per watt is the standard realm of HPS, and, for 2012, 1.5 grams per actual watt (the measurable power unit) is the just-now attainable goal to strive for with LEDs.
 
lenngray, I'm going to disagree with you on this a bit. Any company making a product that last longer than a few weeks will only use a constant current driver for LEDs. Changing the voltage will not change the current. It will change the overall wattage or amperage draw, but not the current. Likewise, no 3 watt LED should ever actually pull 3 watts. There are some red-orange and amber LEDs that use a forward voltage of 3.6 but at 700mA (max current a 3 watt diode should be ran at for a sustained period) it still only pulls 2.52 watts. The reds that SHOULD make up the majority of the panel should pull 1.6-1.8 and most blues will pull 2.1-2.3 watts. I personally feel that luminous flux is a better term then lumens when referring to output of LEDs between 450 and 630nm and Radiometric power (mW) for anything else.

I do think with a custom panel and a lot of fine tuning your grow system to a single strain that 1.5 grams per watt is achievable.
 
Yes, the general concept of the constant-current supply was what I was describing. In fact, the current-supply itself contains an effective resistance and a voltage source -- which needs to be able to increase until the current is as desired. Feedback maintains the target current. But the voltage across that diode does indeed increase as the target current is increased. Maybe only 8% from best to max, but it's a real 8%. A big reason for staying below the max is if you can't keep the temperature of the heatsink down below 110C when running at max. Other than that, it's as I said, it's only to get the best radiant output per watt of supply power.

And no. A "3 watt diode" had better actually be able to run, sustained, at that power or it's being criminally misrepresented as a 3 watt diode. Look at your spec sheets. If it doesn't say that the max has a "duty cycle" less than 100%, then it's a sustained rating.

I agree that the term luminous flux is good, and radiant power does convey the correct things.

But if you're not able to achieve 1.5 grams per watt without "fine tuning", then you're misrepresenting that such LEDs are 50% better than HPS (eg: a 400W LED light matching the yield of a 600W HPS), because it doesn't take such "tweaking" to get to 1 gram per watt with HPS -- just semi-pro agro practices. In fact, if the low heat production of LEDs does not make it easy to add yeast/sugar CO2 production to a grow for increased yield, then maybe LEDs are not what they're being claimed to be at all.

You keep hedging on what an LED system should be able to do, while offering increasing justification for why a manufacturer not even meeting that, should not be questioned.
 
The optimal spectral energy efficiency and maximum growth/watt occurs when the incident light spectrum exactly matches the plants light absorption spectum. Since over 99% of the absorption spectra comes from chlorophyll a and b and beta carotene, an absortion spectra based on their content is pretty close match
The questions I have e what is the pigment content for optimal growth, what is the effect of chlorophyll a:b ratio, and beta carotene ratios on yield and quality, etc.
What I do know is that plants grown in Northern latitudes (Baltic forest tree leaves) have low a:b ratios (from 0.8 to 1.8 /1) and southern latitudes (bushes in southern Spain) are higher (from 5 to 7/1). Also, upper leaves have higher than lower shaded leaves. Beta Carotene levels are higher in southern than northern latitudes.
I made the followng graph to show how the spectral changes with chlorophyll ratio. The biggest change is in the 429/453 peak ratios. Anecdotally, I would say plants grown outdoors in southern areas have higher growth rates and better yield and quality than northern grown and would have high a/b ratio. So that an optimal growlight needs a high 429nm/453nm LEDs ratio which is not available in most lights

Absorption_and_chlorophyll_ratios.jpg
 
Again I disagree. As we spoke about before, the naming of LED 1 3 5 etc watt is based off the drive current used (350 750 1000mA etc.). This is done strickly for simplicity. The voltage across each diode should not change more than 5% unless the system is very poorly designed. Even a 5% voltage change over 2 or 3 volts will ot make much of a change in the diode output. Radiant power is the only way to corrctly discribe >440 and <630 nm leds.

As for achieving 1 gram per watt with HPS and not gettig 1.5 with LEDs, it takes a very large amount of knowlegde experiance and fine tuning to reach 1 gram per watt with HPS. Take a look through the forums. The very experianced growers here rarely get 1+ gram per watt. Take into account most people have been using HPS for the last 20+ years and then attempting to use an LED. LEDs require less water, more air movement, higher CO2, less nuits, and seems to perfer hydro from my experiance. Each difference takes time to get used to. The key with LEDs is the reduction in all power used and not just lighting. Less A/C, less exhaust fans, less power draw from the lights. If HPS growers took all of those things into account I highly doubt ay of them are truly getting 1 gram per watt. I cannot recall a single HPS grow that got 1 gram per watt and counted in the power used in cooling the tent or exhausting heat from the light.
 
The PAR radiation includes all of the known chromaphires and treats them as if they were of equal content when they only are in sum less than 1% of the total, This over emphasis the importance of the middle regions for most plants
 
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