Bad News About LED vs HPS

[iHearAll]

The bulb shouldn't change output since rms is equal in a 60hz as a 60khz. The wire sees the same power aside from the neglegable reactances in the filament and connections. I guess skin effect might take place and would be self limiting after increasing frequency too high. But that would be rather high.

 

[sethimus]

What most people don't know is that the LEDs may last 10 years but the drivers may last about 2 before the capacitor burns out. Might be a wise investment to get fans for the drivers if they're not in a fixture with fans already. I don't know how much the cooling would extend the life though.

quick, somebody go tell meanwell their 7 year warranty will bankrupt them!!!111

 

[ANC]

My advice is at least for the LEDs to avoid active cooling. It is crap loosing LEDs to something small getting into the fan.
I have about 500W LED over a 5x5 area in veg, and when we flip we have 3600W over 11.5 x 13' with a total of 42 COBs at 80W each

Not even costing me a cent, partners supply hardware and electricity I do the growing and caring and premises.

 

[BobCajun]

I think LEDs put out more light than most people would imagine. The trick is to use a simple footcandle meter instead of a fancy light meter. I remembered I had a Rapitest multi testing meter for gardens, which has a light meter as one of the things. Here's an Amazon page for just the light meter by itself.

Full sun is 10,000 fc. According to the meter, one of my little clone veging chambers with a 5w LED bulb puts out 5000 fc at plant top height, about 8000 right at the diffuser. To convert fc to lux you pretty much just multiply by 10, so that would be 50,000 lux in that 5w chamber. That's pretty high. The bulb is only rated as 450 lm. How do you suppose a 450 lm LED cranks out 50,000 lux?

The chamber is about 1 sq ft area, about 1/10th of a sq m, all mylared inside, it's 5000 fc anywhere in that area. Here's where I got the thing about lux being 10x fc. The big flowering chambers are 8000 fc at plant height, with the combination of HPS and LEDs. With the bottom lights I use, it's actually no less than 5000 fc anywhere in there above pot height.

So what do you make of this? Unlikely the light meter could be off by that much. Granted it's cheap but still, somebody would have noticed by now and complained to the company.

 

[wietefras]

My advice is at least for the LEDs to avoid active cooling. It is crap loosing LEDs to something small getting into the fan.

This issue tends to get grossly exaggerated. I've had several issues with powering the fans and there have never been any ill effect for the COBs.

In fact in general they run a lot cooler than passively cooled COBs so ...

 

[wietefras]

So what do you make of this? Unlikely the light meter could be off by that much. Granted it's cheap but still, somebody would have noticed by now and complained to the company.

These things are made to estimate sunlight (usually by measuring mostly the green component) and very poorly at that. They are even less suitable for very different spectral distributions like HPS and Led.

Your measurements could be hugely off depending on the specific spectrum which the sensor is actually sensitive too.

 

[BobCajun]

These things are made to estimate sunlight (usually by measuring mostly the green component) and very poorly at that. They are even less suitable for very different spectral distributions like HPS and Led.

Your measurements could be hugely off depending on the specific spectrum which the sensor is actually sensitive too.

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.

 

[ANC]

This issue tends to get grossly exaggerated. I've had several issues with powering the fans and there have never been any ill effect for the COBs.

In fact in general they run a lot cooler than passively cooled COBs so ...

Tell that to the dead vero29, killed by a piece of string. Yes, they run cooler, until the fan stops.

 

[ZeroTrousers]

Foot candles (candle power) readings are basically the same as lumens, 1 foot candle is something like 10¾ lumens.

The more meaningful measures of the light we need are PAR watts (total watts of like in the major useable spectra) , umol/J and ppfd (how many photons per unit of energy and how many are hitting a given surface).

 

[churchhaze]

"Okay, so I was wrong, but let me keep explaining to you how everything works after changing my argument".

Cognitive dissonance.

 

[BobCajun]

Foot candles (candle power) readings are basically the same as lumens, 1 foot candle is something like 10¾ lumens.

The more meaningful measures of the light we need are PAR watts (total watts of like in the major useable spectra) , umol/J and ppfd (how many photons per unit of energy and how many are hitting a given surface).

That's the common wisdom, but maybe it's just not as good an indicator of a light's effect on plants as a simple photocell. Photocell's do work in a similar fashion to photosynthesis, harvesting visible sunlight, do they not? Well if the photocell is able to get say 8/10ths of the energy from an LED as from the sun then I figure that probably translates fairly linearly to plant photosynthesis energy, that they would get 8/10s of the energy that they get from full sunlight.

 

[BobCajun]

Welcome back professor.

Gilligan? Is that you?

 

[Johnny Lawrence]

smh

 

[ZeroTrousers]

Tell that to the dead vero29, killed by a piece of string. Yes, they run cooler, until the fan stops.

That's why it's ideal to size your heat sinks for passive cooling, but use indirect air movement or even attach fans I like the way you think!

That's the common wisdom, but maybe it's just not as good an indicator of a light's effect on plants as a simple photocell. Photocell's do work in a similar fashion to photosynthesis, harvesting visible sunlight, do they not? Well if the photocell is able to get say 8/10ths of the energy from an LED as from the sun then I figure that probably translates fairly linearly to plant photosynthesis energy, that they would get 8/10s of the energy that they get from full sunlight.

No... that's not the case. PV cells are generally manufactured to take advantage of a wide variety of light spectra and aren't weighted towards what we need. The photo-cell in a lux/lumen meter is specifically doped to be weighted towards how the human eye perceives the visible spectrum.

While your plants do need some green light and blue light, they're too heavily weighted for this and therefore not an accurate measure. The best use of a Lux meter in this kind of horticulture is measuring relative intensity when adjusting light placement - though a decent PAR or quantum meter is far, far more useful for this.

I don't intend any offense, but it seems like you might want to spend some time reading up on this subject.

 

[BobCajun]

Photovoltaic cells are sort of LEDs in reverse, so they may be the perfect thing to measure the light energy output of an LED with. I know it seems wrong to use a calibration based on sunlight but that's all we have. The company does have a meter with a fluorescent setting on it though, I just don't have that model.

 

[ZeroTrousers]

Photovoltaic cells are sort of LEDs in reverse, so they may be the perfect thing to measure the light energy output of an LED with.

While that's exactly how a PV cell works, it's incorrect that they're a good yardstick for usable light output. PAR/quantum meters are far superior.

 

[ANC]

LEDs can act as low power photovoltaics too, you can even use them as buttons using the output.

 

[BobCajun]

Anyway, all I can say is that to a photovoltaic cell a 5w LED in 1 sq ft of space at about 8" distance and surrounded by reflective material is about the same brightness as a greenhouse with fiberglass covering. The plants appear perfectly healthy under them, with some lightening of the margins of new growth due to high brightness. The 5w super grow light is blindingly powerful. At that rate, 50w would cover a sq meter. Just nobody ever attempted to grow with that low a wattage and at close distance using modern high intensity LEDs like in those lightbulbs. Never tried flowering at that wattage though, just clone veging.

 

[BobCajun]

A light measurement called foot-candle hours can be used as a guide for how much light a particular plant needs. The highest on this page is 50,000. In natural light they have to take readings in 4 or 5 hour amounts and average them out because of the changing brightness. With artificial light it's not hard to reach 50,000 or higher. For instance, in my chamber it's 8000 fc at plant tops, with the minus green filter on the HPS btw. Multiplied by 13.5 hours per day yields 108,000 fc hours, over twice what any plant in the list on that page requires. How many fc hours Cannabis needs I don't have a reference for. The page said most plants are at max efficiency with 5000 fc, very easy to get with LEDs.

The rate of photosynthesis is proportional to the light intensity received by the leaf to a maximum of 5000 foot-candles. At 5000 foot-candles, most plants are at 100% efficiency and light intensity levels above this measurement are of little benefit and can only cause heat exhaustion and undue drying of a plant. Therefore, the light meter has been calibrated to 5000 foot-candles.

 

[ZeroTrousers]

Anyway, all I can say is that to a photovoltaic cell a 5w LED in 1 sq ft of space at about 8" distance and surrounded by reflective material is about the same brightness as a greenhouse with fiberglass covering. The plants appear perfectly healthy under them, with some lightening of the margins of new growth due to high brightness. The 5w super grow light is blindingly powerful. At that rate, 50w would cover a sq meter. Just nobody ever attempted to grow with that low a wattage and at close distance using modern high intensity LEDs like in those lightbulbs. Never tried flowering at that wattage though, just clone veging.

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.

A light measurement called foot-candle hours can be used as a guide for how much light a particular plant needs. The highest on this page is 50,000. In natural light they have to take readings in 4 or 5 hour amounts and average them out because of the changing brightness. With artificial light it's not hard to reach 50,000 or higher. For instance, in my chamber it's 8000 fc at plant tops, with the minus green filter on the HPS btw. Multiplied by 13.5 hours per day yields 108,000 fc hours, over twice what any plant in the list on that page requires. How many fc hours Cannabis needs I don't have a reference for. The page said most plants are at max efficiency with 5000 fc, very easy to get with LEDs.

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.