How many watts per square foot?

[Death The Cultivator]

Alas, us DIY types are stuck with learning the hard way, from the plants themselves. Wish I had a PAR meter, but it ain't gonna hoppen at the price. I think I learned a bit about my lights on the current grow. Good news is that they are more than strong enough. Bad news is that they are more than strong enough to cause problems...

Online aquarium let you rent par meters for a week for $40.

 

[Olderfart]

Online aquarium let you rent par meters for a week for $40.

Hi Damian,

Thanks for the head's up. By the time a unit was shipped back and forth to me, the price would be more than I want to spend. For the next grow, I will just start with a lot less power, bring it up very gradually, and watch for stress. I should be able to dial it ok now that the nute screwups are likely sorted, and I have a better idea about where I should end up power wise.

My mistake this time around, I think, was misunderstanding a spec I read online that suggested up to 60 watts/sq.ft., and I built accordingly thinking that the spec applied to full spectrum LED's, which it apparently does not, to say the least. The good news on that front is that my lights now have enough bulbs to let me adjust Kelvin levels without actually changing bulbs. Also, I have enough power for a 3X3 at least if I ever want to up the size of the growdrobe.

Anyway, the current grow is finishing up with some nice bud in spite of me, so lessons learned and bud in the closet - all good.

 

[Olderfart]

They have phone apps. Probably about as accurate as cheap ph meters

Hi Sour. I had a look at someone's instructions on how to use an Android phone, but unfortunately, the tool does not work on an Iphone. I may fiddle with the light meter on my mirrorless camera. I can get actual data from it, so I can compare readings in sunshine with those in the growdrobe. The meter itself may be a bit higher end than the one in my phone too.

OTOH, the plants are pretty good at measuring light input - now that I have a better idea of how to interpret the symptoms, and now that I know that full power on my setup is way too much. We shall see how the next round goes.

Thanks for the head's up.

 

[Sour D]

Hi Sour. I had a look at someone's instructions on how to use an Android phone, but unfortunately, the tool does not work on an Iphone. I may fiddle with the light meter on my mirrorless camera. I can get actual data from it, so I can compare readings in sunshine with those in the growdrobe. The meter itself may be a bit higher end than the one in my phone too.

OTOH, the plants are pretty good at measuring light input - now that I have a better idea of how to interpret the symptoms, and now that I know that full power on my setup is way too much. We shall see how the next round goes.

Thanks for the head's up.

Hunh! I'll have to check out my camera as well. Thanks for the idear

 

[Olderfart]

Hunh! I'll have to check out my camera as well. Thanks for the idear

The thing with the camera is that by recording the f stop and shutter speed (always at the same ISO setting - beware automatic ISO, that will screw you up the same way a lot of phone cameras do), you have an exact and repeatable measure of light level. You will have to use a grey or white card in the image and orient it similarly all the time to get comparable readings. If you can get next to someone else's par meter for a while, you could even calibrate it to later use the camera in the grow setup. The camera will not measure PAR exactly, but I bet that it would be close enough to get you in the ballpark without investing in the higher end meter.

You could accomplish much the same with a good incident light meter if you happened to have one of them around, but I suspect that recent digital camera meters might work better. The new meters may have to keep track of broader spectrum due to the sensitivity of the digital sensors. Just theory at this point...

OTOH, one could just watch for praying and tacoing...

Have fun!

 

[Death The Cultivator]

Hi Damian,

Thanks for the head's up. By the time a unit was shipped back and forth to me, the price would be more than I want to spend. For the next grow, I will just start with a lot less power, bring it up very gradually, and watch for stress. I should be able to dial it ok now that the nute screwups are likely sorted, and I have a better idea about where I should end up power wise.

My mistake this time around, I think, was misunderstanding a spec I read online that suggested up to 60 watts/sq.ft., and I built accordingly thinking that the spec applied to full spectrum LED's, which it apparently does not, to say the least. The good news on that front is that my lights now have enough bulbs to let me adjust Kelvin levels without actually changing bulbs. Also, I have enough power for a 3X3 at least if I ever want to up the size of the growdrobe.

Anyway, the current grow is finishing up with some nice bud in spite of me, so lessons learned and bud in the closet - all good.

Max is 50 watts per sqft but at that point c02 might be a consideration. I've rented one twice for my DIY builds as anything that didn't measure PAR was inaccurate and it was a great help in devising a lighting spread.

 

[Olderfart]

Max is 50 watts per sqft but at that point c02 might be a consideration. I've rented one twice for my DIY builds as anything that didn't measure PAR was inaccurate and it was a great help in devising a lighting spread.

If I could rent one locally, I would be on it in a heartbeat. I may ask the local garden center dude if he knows anyone around here that has one. If I can get hold of one, I certainly will. It would be really interesting to measure the par output of my el cheapo light setup. Once calibrated, I would be off to the races with the good data that you and others point to.

In the meantime, I have learned to read the tacoing, I think.

Thanks for the input Damien, much appreciated.

 

[Death The Cultivator]

If I could rent one locally, I would be on it in a heartbeat. I may ask the local garden center dude if he knows anyone around here that has one. If I can get hold of one, I certainly will. It would be really interesting to measure the par output of my el cheapo light setup. Once calibrated, I would be off to the races with the good data that you and others point to.

In the meantime, I have learned to read the tacoing, I think.

Thanks for the input Damian, much appreciated.

You'd have better luck at an aquarium. Good luck though it's a great tool.