Lux Meter Useful for White LEDs?

algebraist

algebraist

Well-Known Member
I've read that you can't use a lux meter with LEDs, which made sense thinking about the "blurple" LEDs. But I don't see why it wouldn't be useful with COBs and other white light LEDs. (I know that a PAR meter would be better, but I'm looking for a relatively cheap way to gauge how much light I'm getting at the canopy.) Thanks in advance for any advice.
 
algebraist

algebraist

Well-Known Member
Thanks; guess I should have been more specific about what I want to do. I'm planning a DIY light build, and I'm looking to measure how much light the plants are receiving at the canopy, to compare it to whatever I can find about optimum or maximum light levels. (So far all that I've found is a table on growweedeasy.com that suggests 40,000 - 70,000 lux for vegetative growth, and 60,000 - 85,000 lux for flowering.) Basically I'd like to buy some COBs or white LED strips, wire them up, hang them, and stick a meter about a foot below them and see what it says, then tweak the design accordingly. I'm planning to put the whole thing on a dimmer, so too much light is not a real problem (except in cost), but too little would be a shame...
 
tomate

tomate

Well-Known Member
Forget about the lux.
If you get some decent COBs, you can calculate ur avg. PPFD and the system efficiency.

~500 veg
<1000 flower
 
BuddyColas

BuddyColas

Well-Known Member
algebraist said:
Thanks; guess I should have been more specific about what I want to do. I'm planning a DIY light build, and I'm looking to measure how much light the plants are receiving at the canopy, to compare it to whatever I can find about optimum or maximum light levels. (So far all that I've found is a table on growweedeasy.com that suggests 40,000 - 70,000 lux for vegetative growth, and 60,000 - 85,000 lux for flowering.) Basically I'd like to buy some COBs or white LED strips, wire them up, hang them, and stick a meter about a foot below them and see what it says, then tweak the design accordingly. I'm planning to put the whole thing on a dimmer, so too much light is not a real problem (except in cost), but too little would be a shame...
Click to expand...
So check out this thread: https://www.rollitup.org/t/par-multiplier-thread.928907/
All I have is a LUX meter. With the conversions, you can come pretty close to getting a ballpark PAR reading. A LUX meter is great for adjusting spacing and height for the most uniform spread. What type of cobs are you planning to run?
 
algebraist

algebraist

Well-Known Member
BuddyColas said:
What type of cobs are you planning to run?
Click to expand...
Top of the list at the moment are the Bridgelux EB strips -- reasonable prices, available, pretty good efficiency (about 156 lm/w), and they don't need heat sinks. And the strip configuration is appealing for getting an even spread.
 
BuddyColas

BuddyColas

Well-Known Member
algebraist said:
Top of the list at the moment are the Bridgelux EB strips -- reasonable prices, available, pretty good efficiency (about 156 lm/w), and they don't need heat sinks. And the strip configuration is appealing for getting an even spread.
Click to expand...
I'm a big fan of the EBs. I run them at test with no heat sink, and at 1.5 times test with a heat sink. I like the 3k for everything at 35ish watts per sq ft.
 
algebraist

algebraist

Well-Known Member
BuddyColas said:
I'm a big fan of the EBs. I run them at test with no heat sink, and at 1.5 times test with a heat sink. I like the 3k for everything at 35ish watts per sq ft.
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Apologies for my ignorance -- first build, still trying to figure out what to do -- does "at test" mean at their "nominal current" of 700mA (for the 22" or 44" strips), so that "1.5 times test" would be in the neighborhood of 1000mA?

Still deciphering, by "3k" you're talking about the 3000K (color temperature)?

And lastly, exactly the information I've been looking for, "35ish watts per sq ft." -- so for my 8 square foot tent, about 280 watts. Which, if I decide on 700mA, for example, turns into 15.5W per 22" strip, so I'd need about 18 strips. I have no idea -- would that be all anyone could want for flowering? Thanks very much.
 
BuddyColas

BuddyColas

Well-Known Member
algebraist said:
Apologies for my ignorance -- first build, still trying to figure out what to do -- does "at test" mean at their "nominal current" of 700mA (for the 22" or 44" strips), so that "1.5 times test" would be in the neighborhood of 1000mA?

Still deciphering, by "3k" you're talking about the 3000K (color temperature)?

And lastly, exactly the information I've been looking for, "35ish watts per sq ft." -- so for my 8 square foot tent, about 280 watts. Which, if I decide on 700mA, for example, turns into 15.5W per 22" strip, so I'd need about 18 strips. I have no idea -- would that be all anyone could want for flowering? Thanks very much.
Click to expand...
Yes 700ma is nominal. And 1.5 nominal is 1000ma. Bridge luxe over builds their cobs/strips and under reports their specs. And 35ish watts is about 800 par. Plenty for me, but some are not happy with less than 1000 par. That is the cool thing about the EBs. Build your fixture for say 30ish watts a sq ft nominal on good heat sink, then you can drive them to 45 watts a sq ft no problem.

Check post 321 in the EB thread. That's what I did for a heat sink and fixture.
 
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ANC

ANC

Well-Known Member
algebraist said:
I've read that you can't use a lux meter with LEDs, which made sense thinking about the "blurple" LEDs. But I don't see why it wouldn't be useful with COBs and other white light LEDs. (I know that a PAR meter would be better, but I'm looking for a relatively cheap way to gauge how much light I'm getting at the canopy.) Thanks in advance for any advice.
Click to expand...
Check your local pet shop that sells equipment for planted aquariums, many of them rent out par meters.

Any of you looked into driver free COBs yet? Efficiency isn't stellar (100lm/W), but it rips up to a 3rd out of build cost.
 
KonopCh

KonopCh

Well-Known Member
Guys... It's better to have COBs on buds or just on plant/leaves for maxximum yield? In flower of course.
 
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