Think ive been led astray

Stephenj37826 said:
Angling it twords the light exposes more surface area of the sensor. I can tell you from experience that the numbers are alot higher if you aim it at the light vs straight up.
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That's because those readings are more accurate. All my plants in my garden, inside and out, reach and look towards the light. They are not fixed to looking straight up, why should the sensor?
 
If you as a person are looking directly at the sun, it's pretty bright right? If you angle your eyes 90 degrees perpendicular to the sun, then there is much less light entering your eyes and it's not as bright. That doesn't negate the fact that extreme intensity is still there. You just aren't looking at it directly. Well plants do look at the light source directly. That is why IMO readings are more telling when the highest reading achieved is logged.
 
cdgmoney250 said:
If you as a person are looking directly at the sun, it's pretty bright right? If you angle your eyes 90 degrees perpendicular to the sun, then there is much less light entering your eyes and it's not as bright. That doesn't negate the fact that extreme intensity is still there. You just aren't looking at it directly. Well plants do look at the light source directly. That is why IMO readings are more telling when the highest reading achieved is logged.
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I'm not denying that as a tool in your personal garden you probably should angle it. To have a fair apples to apples comparison of diffrent lights you have to use the same standard measuring techniques. The standard way to test a light for comparison purposes is to only measure with the sensor flat.
 
Stephenj37826 said:
He's saying 240 watts 24000 lumens. Don't sound like they use a very high bin cxb and/or terribly inefficient drivers. Doesn't sound any better than Chinese high bays if those numbers are correct.
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Yeah that is pretty weird, considering that Cree supposedly has LEDs that produce 303 lm/w http://www.cree.com/News-and-Events/Cree-News/Press-Releases/2014/March/300LPW-LED-barrier
I don't know what the LEDs are that they're talking about though. I don't know why those high-bays are putting out such low lumens. Maybe the CXBs aren't the highest output, just the best dollar per lumen deal. Maybe the 303 lm/w ones cost a fortune.
 
BobCajun said:
Yeah that is pretty weird, considering that Cree supposedly has LEDs that produce 303 lm/w http://www.cree.com/News-and-Events/Cree-News/Press-Releases/2014/March/300LPW-LED-barrier
I don't know what the LEDs are that they're talking about though. I don't know why those high-bays are putting out such low lumens. Maybe the CXBs aren't the highest output, just the best dollar per lumen deal. Maybe the 303 lm/w ones cost a fortune.
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303 lm/W LEDs are far from mass production.
The Cree CXB high bay lights should not be confused with the Cree CXB COBs...
 
alesh said:
303 lm/W LEDs are far from mass production.
The Cree CXB high bay lights should not be confused with the Cree CXB COBs...
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Looks like it has COBs in it. Also seems to have a nice fairly even beam. I guess they must be 20 watt COBs because there's 12 of them. This video is a year old. I'm surprised Cree is still on that model actually. But yeah, the 303 lm/w ones are probably far from commercial production and that reading is also probably not what you would actually get from a lamp made with them. Those were probably ideal conditions. I don't know why SK is still using the older LEDs though, since these CXB high-bays are at least a year old now and apparently cheaper. SK is just not keeping up.

 
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Actually I guess those couldn't be cobs that small, just high wattage LEDs. Don't know what I was thinking there.
 
BobCajun said:
Actually I guess those couldn't be cobs that small, just high wattage LEDs. Don't know what I was thinking there.
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No those are cobs just not the largest ones 3070/3590. They make much smaller cobs.


That being said it seems everyone wants a high bay to be a grow light. A good purpose built cob led grow light is the best idea. There are great options out there.
 
BTW peoples, in many of CREE's commercial lighting products they uses in-house custom LED/COBs that are only available on those products. They're usually based on existing lines and tweaked to work better with the design of the light and it's purpose. And that's according to several CREE salespeople I've met over the last year. The light Bob posted to is basically an M-COB or Multi-COB design and may or may not be perfect for growing. Mid-size CREE LEDs are already doing 170+ lumens per watt performance but you would need so many of them to get the intensity one would need to grow that it just wouldn't be worth it.
 
Stephenj37826 said:
No those are cobs just not the largest ones 3070/3590. They make much smaller cobs.


That being said it seems everyone wants a high bay to be a grow light. A good purpose built cob led grow light is the best idea. There are great options out there.
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Oh, okay, thanks for clearing that up. However, if you look at this video you'll see that the light is only at high enough PAR where the beams of the two cobs overlap. That tells me that you need to focus two cobs on the same spot at about 16-18" down so they form one bright round area of decent intensity. A single cob's beam is not suficiently intense. It would be less than 500 PAR, I'm guessing, since the overlapped area is about 980.

You would also need to grow in a round area to match the beam shape. Overlapping a bunch of beams would create more bright spots rather than a uniform square of light. Though actually since the LEDs in the cobs are arranged in a square shape, as far as I know, I guess it's the round lens that makes the beam round. Maybe the plain cobs would make a square beam. Somebody should make a square lens, if that's possible.
 
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BobCajun said:
Oh, okay, thanks for clearing that up. However, if you look at this video you'll see that the light is only at high enough PAR where the beams of the two cobs overlap. That tells me that you need to focus two cobs on the same spot at about 16-18" down so they form one bright round area of decent intensity. A single cob's beam is not suficiently intense. It would be less than 500 PAR, I'm guessing, since the overlapped area is about 980. You would also need to grow in a round area to match the beam shape. Overlapping a bunch of beams would create more bright spots rather than a uniform square of light. Though actually since the LEDs in the cobs are arranged in a square shape, as far as I know, I guess it's the round lens that makes the beam round. Maybe the plain cobs would make a square beam. Somebody should make a square lens, if that's possible.
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I still feel the proper use of cobs would be as others have stated in the the early DIY posts, 1 cob per 12-18" diameter of grow area
 
OneHitDone said:
I still feel the proper use of cobs would be as others have stated in the the early DIY posts, 1 cob per 12-18" diameter of grow area
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Okay but what's the par reading under one 82w (or whatever it is) cob's circular beam? I mean with no overlapping.
 
cdgmoney250 said:
So after some data logging, the results are in... I will let you guy's come to your own conclusions. I'm doing this because I have access to both the lamp and the tools.
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Thank you for taking the time to do this testing. It is interesting that as the lamp is raised the average PPFD drops off, I assume this is due to scatter/absorption in the walls. Looks like 24" is ideal?

One thing I have been curious about the SK is the temp droop. Was the lamp fully warmed up before the test (30-60 minutes maybe)

As far as angling the senor, I noticed that the Apogee sensor handles the high angle incident light better than my lux meter but I agree the numbers go up quite a bit when you point it at the light, even with the Apogee sensor. I guess that would be especially true when the light is closest to the canopy and there is a large proportion of high angle incident light.
 
SupraSPL said:
Thank you for taking the time to do this testing. It is interesting that as the lamp is raised the average PPFD drops off, I assume this is due to scatter/absorption in the walls. Looks like 24" is ideal?

One thing I have been curious about the SK is the temp droop. Was the lamp fully warmed up before the test (30-60 minutes maybe)

As far as angling the senor, I noticed that the Apogee sensor handles the high angle incident light better than my lux meter but I agree the numbers go up quite a bit when you point it at the light, even with the Apogee sensor. I guess that would be especially true when the light is closest to the canopy and there is a large proportion of high angle incident light.
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That's not the average PPFD - it's the average of the measured values. It isn't the same thing.
But yeah higher the lamp is more photons are lost due to scatter/absorption in the walls.
 
SupraSPL said:
As far as angling the senor, I noticed that the Apogee sensor handles the high angle incident light better than my lux meter but I agree the numbers go up quite a bit when you point it at the light, even with the Apogee sensor. I guess that would be especially true when the light is closest to the canopy and there is a large proportion of high angle incident light.
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Why would you NOT aim the meter at the light? The plants are going to turn their tops and leaves to face the light so logically you should do the same with the sensor. The readings should also be taken at the corners of the squares, not the middles (not directing these comments to you personally, SupraSPL, but whoever is doing the readings). We need to know what the intensity is at the outside edges of various sized grow spaces. Grow tents don't come in 2.5 and 3.5 foot sizes. Well they probably do but most people get the even foot sized ones I would think.
 
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