Lets Talk Inexpensive PAR Meters....

Evil-Mobo

Evil-Mobo

Well-Known Member
JorgeGonzales said:
Picture it like this. A lux meter weighs every photon arriving at it's sensor, and gives the most weight to green with a peak at about 550nm, right? Because that's how our eyes work.

So pretend you have a meter that only reads green light. You have two lights, Light A is 50/50 green and blue, Light B is 100% green light. They are making the same amount of light but your meter says Light A is half as powerful. This is the problem using lux meters to compare two lights, in a worst case scenario.
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What about just for the purpose of checking how even the light you have hanging is hitting the canopy? For this use is it OK, because the lux meters are a lot cheaper than the good PAR meters................
 
alesh

alesh

Well-Known Member
Evil-Mobo said:
What about just for the purpose of checking how even the light you have hanging is hitting the canopy? For this use is it OK, because the lux meters are a lot cheaper than the good PAR meters................
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No problems with this purpose.
 
alesh

alesh

Well-Known Member
JorgeGonzales said:
Picture it like this. A lux meter weighs every photon arriving at it's sensor, and gives the most weight to green with a peak at about 550nm, right? Because that's how our eyes work.

So pretend you have a meter that only reads green light. You have two lights, Light A is 50/50 green and blue, Light B is 100% green light. They are making the same amount of light but your meter says Light A is half as powerful. This is the problem using lux meters to compare two lights, in a worst case scenario.
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I'd be quite interested in how similar a (cheap) lux meter sensor's response is to the luminosity function and which spectrum it is correlated with.
 
HydroRed

HydroRed

Well-Known Member
PurpleBuz said:
if you can afford a wee bit more, I suggest using the apogee sq-100, sq-200. Will do better than a lux meter, While the apogee is weak in the deep red region, it at least doesn't bias it into the narrow human lumens bandwidth. With the wide variety of spectrums that different grow lights are producing nowadays seems prudent to not use a lux meter, unless all of your lights have a very similar spectrum.
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Thanks for this.....I wasnt even taking spectrum into consideration. Evey led light I have and plan to build/add on is 3500K. No far reds/blues etc.
 
C

churchhaze

Well-Known Member
If you want to know how relatively bright it is (for checking how well lighting is distributed), you can attach a photo cell to a multi meter with alligator clips and move the cell around the canopy. Extremely crude, but by far cheaper than getting a meter.


http://www.amazon.com/SUNKEE-Sensitive-Resistor-Photoresistor-Optoresistor/dp/B00AQVYWA2?ie

Tie it to an A/D converter on an arduino and you can do some calibration/linearization too. Still not a good light meter, but can check "which spot is brighter" on a canopy.
 
Sevren

Sevren

Well-Known Member
I've been interested in an inexpensive PAR/quantum meter myself, but seems silly to spend $200-$400 just to make sure my light is at the right height and getting a good spread of µmols on the canopy. I'm also using 3 different CCTs, but it seems like that doesn't matter by the responses here. Or does it?
 
BOBBY_G

BOBBY_G

Well-Known Member
Sevren said:
I've been interested in an inexpensive PAR/quantum meter myself, but seems silly to spend $200-$400 just to make sure my light is at the right height and getting a good spread of µmols on the canopy.
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really? because assuming your garden is 4x4 or bigger it should pay for itself pretty quickly
 
OneHitDone

OneHitDone

Well-Known Member
Ok ok, par, ppf, ppfd canopy talk.
This is not HID vs led talk.
Anyone have a logical way to explain what one might be seeing for µmol's at the canopy in a setup like this?
I can't wait till someone comes up with a corncob that can be hung like those 1000's :bigjoint:

 
P

PurpleBuz

Well-Known Member
OneHitDone said:
Ok ok, par, ppf, ppfd canopy talk.
This is not HID vs led talk.
Anyone have a logical way to explain what one might be seeing for µmol's at the canopy in a setup like this?
I can't wait till someone comes up with a corncob that can be hung like those 1000's :bigjoint:
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I can build cob lights that will have a full sideways radiation pattern. kind of like a bare hanging incandescent bulb or a CFL
that would sit between the tree tops. Is that really useful ? Seems wasteful unless your smack in the middle of the grow area.
 
OneHitDone

OneHitDone

Well-Known Member
PurpleBuz said:
I can build cob lights that will have a full sideways radiation pattern. kind of like a bare hanging incandescent bulb or a CFL
that would sit between the tree tops. Is that really useful ? Seems wasteful unless your smack in the middle of the grow area.
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Do you have any examples of those builds?

Yes it seems wasteful, dudes plants in vid are clearly not using his lamps efficiently? bongsmilie
I was trying to see what others feel is realy going on there with the photons being used in a "non conventional" fashion like that. It flies in the face of all of the math constantly regurgitated here in this forum.
 
P

PurpleBuz

Well-Known Member
OneHitDone said:
Do you have any examples of those builds?

Yes it seems wasteful, dudes plants in vid are clearly not using his lamps efficiently? bongsmilie
I was trying to see what others feel is realy going on there with the photons being used in a "non conventional" fashion like that. It flies in the face of all of the math constantly regurgitated here in this forum.
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I haven't built one. I can do it as a light bar or as an individual lamp. would look very similar to a traditional Edison bulb.
It makes some sense for a naked hps bulb since most of the reflector penalty is eliminated,
 
OneHitDone

OneHitDone

Well-Known Member
PurpleBuz said:
I haven't built one. I can do it as a light bar or as an individual lamp. would look very similar to a traditional Edison bulb.
It makes some sense for a naked hps bulb since most of the reflector penalty is eliminated,
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That's what has me interested. Reflector loss is eliminated but clearly intensity goes down as well. Replaced by a lower intensity in all directions.
Yet, some of the biggest most beautiful plants on the tube. Makes one think maybe high intensity of 1000µmoles straight down over the whole canopy is not the answer to growing big dank marijuana plants
 
P

PurpleBuz

Well-Known Member
OneHitDone said:
That's what has me interested. Reflector loss is eliminated but clearly intensity goes down as well. Replaced by a lower intensity in all directions.
Yet, some of the biggest most beautiful plants on the tube. Makes one think maybe high intensity of 1000µmoles straight down over the whole canopy is not the answer to growing big dank marijuana plants
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it gives a lot of side lighting which has its advantages, I can see usage as intrAcanopy lighting between rows of trees.
 
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J

JungleTime

Well-Known Member
Honestly just use a light meter app? Just search light meter in the app store and you should be able to get a pretty good idea. If you want a par meter that actually works your going to shell out some chedder. With this free app you can measure foot candles rather than par. Its debatable about how many foot candles equals plant usable light but if you have grown you should be able to know if you have enough light and using this app you can see what part of your canopy is lacking.

Brand new 1000w hortilux bulbs are roughly 50k-60k right dead in the middle.
 
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