Bad News About LED vs HPS

BobCajun

Well-Known Member
OK, this is plain wrong.

Sunlight is something like 98000 lux per square meter@ sea level, which works out to around 9100 lux per square foot - that's about 4260 lux higher than a 4000k CLU048-1212C4 running @ 1400ma (4840lm). These chips are around 40-45% efficient at that drive current, which is a hair under 50W. Here's the datasheet.

http://ce.citizen.co.jp/lighting_led/dl_data/datasheet/en/COB_6/CLU048-1212C4_P3949_0217_170410.pdf

my Veros produce around 12590lm @ ~81.3W. If you scale that back to 50W, that's about 7700lm @ 50w consumption (154 lm/w, rounding down). Here's the data sheet for that.

http://www.bridgelux.com/sites/default/files/resource_media/DS93 Vero 29 Array Data Sheet Rev A 20160622.pdf

So, somehow you've managed to obtain a 5w LED that 's making at least 1250lm/watt (or well over 500% efficient). That's unbelievable.

Literally, I do not believe it.

I'd believe you're producing 6700lm @ 50w with a CXB or similar emitter though.




Again, this doesn't address the fact that Foot Candles is an extremely out of date measure for light production. HPS weights much more heavily on this scale than natural sunlight due to the high fraction of green and yellow light. This is a relative measure for the purpose of determining light source brightness for the human eye. It does not take into account total photon production, nor the efficiency of the given spectrum for photosynthesis. This is why Quantum and PAR meters exist. Stop moving the goalposts on this argument.
You would think, but the Rapitest meter says otherwise, and I do grow plants with the 5w LED bulb. For those on a budget, it's a handy item, the Rapitest. An interesting thing I learned is how little light plants really need, 5000 fc. Maybe dim light distributed around the canopy would be better than using very high wattage above to try to blast through the upper layers.
 

Rahz

Well-Known Member
5000 FC should translate to around 1000 PPFD which is pretty strong. I can see a meter registering 5000-8000 FC directly under a 5w led, but if you're reading 5000 across a square foot your meter isn't giving a good reading.
 

mauricem00

Well-Known Member
Can't afford it. I'm a poor person. This one seems to suffice anyway. It eased my mind that the minus green filter didn't cut too much light out from the HPS.
don't feel bad. I use the same meter for relative measurements to insure I have uniform coverage . mine only goes up to 2000 but I don't know what its calibrated in. silicon photo cells have a response curve that matches the quantum curve so the longer the wavelength the higher the reading for a given input power and cheap light meters have no filters to modify the response so 1 watt of light at 700nm will read as 1.75 times the power of 1 watt at 400nm. as long as your 5 watt LED does a good job of "sprouting" clones nothing else really matters.people who pretend to understand quantum theory are very entertaining to those of us who do understand it.( I don't believe it but I do understand it :) )the only thing that really matters is how well a light grows plants. and that is effected by many factors. light is only one of them. some strains grow better under LEDs than others.
 

BobCajun

Well-Known Member
5000 FC should translate to around 1000 PPFD which is pretty strong. I can see a meter registering 5000-8000 FC directly under a 5w led, but if you're reading 5000 across a square foot your meter isn't giving a good reading.
My 5w in the reflector is 5000 fc at 9" from the diffuser, anywhere under it in a sq ft, meaning the size of the reflector itself, the upper half of the chamber. At 18" it drops to 3000, at 24" 2000, at 36"1200. However at 48" away it's down to about 500 fc. Plants need at least 1000 so I can't recommend running your 5w grow light any farther from the canopy than 36", sorry.

BTW it's the mini LED bulbs I'm using in the clone veging chambers. They're only 1.75" across the diffuser. They fit a normal lightbulb socket but are much smaller than normal lightbulb size. I find they work well and are a lot less bulky to store and work with. hard to find though. I only ever saw them in a dollar store I go to. Pretty expensive for a dollar store too, $4. Must be high quality. Luminus brand, or knockoff, whatever. They're good ones anyway. 2700k btw.
 
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InTheValley

Well-Known Member
Here are my numbers on this,

First off, my Par meter was calibrated with A-Mars factory, B- Mars with lenses, Mars300 with lenses is 1500 par at 18inches, No BS, unreal huh? Thats without messing with the spectrum. I replaced over 40 diodes to 4000k and 6 Fullspectrum 3W diodes, this rig is running at 125 watts at the wall

12inches-1999 MAXED
LUX=80,000

18in- 1300 PAR
47,000 LUX

24in 800 par
29,000 lux

33 in 450 par
16,000 LUX

My scrog is at 33 inches.

and at 33inches, its only 1500 FC and 4,500 FC at 18inches
 

nfhiggs

Well-Known Member
OK, this is plain wrong.

Sunlight is something like 98000 lux per square meter@ sea level, which works out to around 9100 lux per square foot - that's about 4260 lux higher than a 4000k CLU048-1212C4 running @ 1400ma (4840lm). These chips are around 40-45% efficient at that drive current, which is a hair under 50W. Here's the datasheet.
Lux is, by definition, a measure of light intensity per square meter. There is no such thing as "lux per square foot" You are also conflating Lux and Lumens which are totally different kinds of light measurements.
 

nfhiggs

Well-Known Member
the longer the wavelength the higher the reading for a given input power and cheap light meters have no filters to modify the response so 1 watt of light at 700nm will read as 1.75 times the power of 1 watt at 400nm.
I believe you have that backwards. Higher frequency = higher energy. Longer wavelength = lower frequency, and lower energy.
 

Rahz

Well-Known Member
Higher nm light has more photons per watt, less energy per photon. It's always the same power per watt of course, but a meter that measures photons will give higher readings under warmer light if the output wattage is the same.
 

nfhiggs

Well-Known Member
I believe you have that backwards. Higher frequency = higher energy. Longer wavelength = lower frequency, and lower energy.
Ahhh... I know what the problems here is. Meters count photons, not watt energy. More photons in a watt of low energy light, than a watt of high energy light. You are indeed correct.

My bad.
 

InTheValley

Well-Known Member
Here is today, after i pulled the hermie, and tucked moreeeee tops. and i also GML'd the one in the 36oz cup

I have 32 holes filled, and done tucking.

This was a "lets see what happens" Mars300watt mod. Inspired by Niel and Black diamond, LOL.

The light is freakin intense, and wish i had a dimmer.

I have no clue how this is going to turn out, im expecting lanky buds, but its a great spectrum for veg, If i let this veg for 50 days, it would be a monster under this light. It had really giant fan leaves, and i cut the pedals off, and left maybe 10% of the leaf. Seemed to have zero effect on growth, even doing 7-8 at once. No stress. If you look close at the pic, you can see the leaves cut, looks like GrowMau5 headgear, LOL.

SO, we will see what these look like in 10 weeks i suppose. While I gather the stuff for my next light, 20 LED strips.
 

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nfhiggs

Well-Known Member
Higher nm light has more photons per watt, less energy per photon. It's always the same power per watt of course, but a meter that measures photons will give higher readings under warmer light if the output wattage is the same.
Yeah, I figured it out after looking at that a little while later.
 

wietefras

Well-Known Member
Nonetheless, it's enough light to mimic close to sunlight intensity on the meter, which is calibrated to sunlight. Maybe people were over complicating the light measurement. Maybe they just needed a Rapitester. Considering the 5w LED can bleach new growth in those chambers, I'm inclined to believe the meter, that it's 50,000 lux in there.
No, that's not how it works. They are calibrate to sunlight, but they still tend to focus on measuring the green part of the spectrum and then extrapolate that to a expected total amount of light if it was indeed sunlight hitting the sensor. So if there is less green light in the spectral distribution of the light source used, you will get completely incorrect measurements.

It doesn't matter if you measure foot-candle or lux. It's both based on the same green centric measurement. Only difference is that lux is 10 times higher than fc. Both are useless in measuring and comparing different spectrum lights unless you know the specific conversion factor for each spectrum used and apply that correction factor.
 

Jimdamick

Well-Known Member
i too have had negative effects. if my tops get 6-12" from a 75W COB they get so fat that they tend to fall over
If my knob gets 6-12" inches from a 38 DD it falls over too, with a splash
Now my bud. under an LED, vs HID, it doesn't seem to work that way.
Heat intensity is the main difference between LED, and HID, so in your average grow "closet", HPS is a loser.
I have enough room to dissipate the heat in one room, but not so in another. I have to choose 1 room to run for my next cycle, and for weight and quality, I choose HID.
No comparison.
 

Yodaweed

Well-Known Member
Here is today, after i pulled the hermie, and tucked moreeeee tops. and i also GML'd the one in the 36oz cup

I have 32 holes filled, and done tucking.

This was a "lets see what happens" Mars300watt mod. Inspired by Niel and Black diamond, LOL.

The light is freakin intense, and wish i had a dimmer.

I have no clue how this is going to turn out, im expecting lanky buds, but its a great spectrum for veg, If i let this veg for 50 days, it would be a monster under this light. It had really giant fan leaves, and i cut the pedals off, and left maybe 10% of the leaf. Seemed to have zero effect on growth, even doing 7-8 at once. No stress. If you look close at the pic, you can see the leaves cut, looks like GrowMau5 headgear, LOL.

SO, we will see what these look like in 10 weeks i suppose. While I gather the stuff for my next light, 20 LED strips.
Those things are looking pretty stretchy
 

InTheValley

Well-Known Member
Those things are looking pretty stretchy
Yeap, i agree. Like i said, Its a test of seeing what happens till i get my lights done.

Might be the genetics to tho. The plant i had to chop was pretty short and stout and didnt stretch much. I know these are different strains tho, because small cup was fast to show at 10 days, the one in the large container took 15 days to show,

I started with 12 plants, lol, had to eliminate as the days went/.

also, the one in the cup was always furthest from the light, I had the light 40 inches away most of the time.
 

BobCajun

Well-Known Member
Lux is, by definition, a measure of light intensity per square meter. There is no such thing as "lux per square foot" You are also conflating Lux and Lumens which are totally different kinds of light measurements.
Yeah it would be lumens per sq ft rather than lux, lux is not per anything, it's one lumen lighting one sq m of surface. A foot-candle is in fact 1 lumen /sq ft, hence the 10x conversion factor, a sq m being a little over 10 sq ft.
 
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