1KTrees
Member
Based on COB tech that's a good sweet spot over 18par watts per sqft.
DIY with Quantum Boards
- Thread starter robincnn
- Start date
ttystikk
Well-Known Member
Twice that wattage was entirely enough for 24 sq ft.
1KTrees
Member
333par watts over 24sqft. sounds like a fish tale. Lol!
ttystikk
Well-Known Member
2x330=670W over 24 sq ft.
1KTrees
Member
The above quote was 320 actual watts and you said twice that would cover 24 sqft. (640w). That would be about 14par watts (25.8real watts)per sqft. which seems fairly low. 333par watts total.
Until there are enough posted FULL/COMPLETE grows we won't know until we know. Hopefully you are correct.
BobCajun
Well-Known Member
So boards only get warm to the touch, that's perfect. Heat Sinks were one of the biggest downsides of COBs. The boards are plug & play, just need some kind of frame to hold them, a driver, and that's it. The only thing COBs would be better for is if it's open space and you need a focused beam.
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ttystikk
Well-Known Member
True, mine wasn't completed. It got far enough along that I'm still confident in my assertions.
Danielson999
Well-Known Member
There has been at least a few grows I've seen around here with cobs that have done well with 20-25 real watts per sqft. If I remember correctly Supra or Growmau5 have tried it.
ttystikk
Well-Known Member
I've been running 38W/sq ft and my next setup will run 675/24=28W/sq ft. All these numbers are actual from the wall Watts drawn, drivers and all.
1KTrees
Member
I don't have the exact figures but I think your current COBs have 50% or higher eff. so you have 38w/sq ft which would be 19+par watts/sq ft.
Going down to 14+par watts per sq ft. "Fingers Crossed"
BuddyColas
Well-Known Member
I run 15 par watts a sq. ft. all the time for about 750ppfd for warm cobs. That is enough to get 1.5 oz a square foot...very productive...so 15 par watts a sq. ft. is quite adequate...in my opinion and from my experience.
kmog33
Well-Known Member
lukio
Well-Known Member
im pleased for them but sad for my plants as I blooming missed the latest drop/bin
BobCajun
Well-Known Member
You don't need much wattage really. 25w of LED is about the same as 40w of fluorescent, which was the upper amount recommended for them. I had 216w of COBs in a 3'x1.5' chamber (mylar all around) and it was clearly excessive, with bleaching and burning being common. Then recently I put my Arduino on there at a 75% duty cycle, 300 ms on, 100 ms off, and growth is as vigorous plus leaves are darker and plants look less burnt on the tips. I won't know about yield for a while though.
I think PWM may be better for plants than a simple variable resistor, because when it's on it's on full power. Whether that actually makes a difference I don't know but maybe. BTW you can hook up more than one driver to the same Arduino, I have 2 hooked up to one. You just attach them in parallel like with other dimmers. You need an optocoupler or some such thing to hook Arduinos to drivers of course, due to the different voltage involved.
That particular duty cycle is in the range that was reported in a study to increase plant yield over steady light. I just used the highest end of the range because the others would dim it more than I want. 75% seems about right to me. Whether the on/off cycle really boosts growth is debatable but it's worth a shot. Considerably less heat being put off by the sinks now too.
I think PWM may be better for plants than a simple variable resistor, because when it's on it's on full power. Whether that actually makes a difference I don't know but maybe. BTW you can hook up more than one driver to the same Arduino, I have 2 hooked up to one. You just attach them in parallel like with other dimmers. You need an optocoupler or some such thing to hook Arduinos to drivers of course, due to the different voltage involved.
That particular duty cycle is in the range that was reported in a study to increase plant yield over steady light. I just used the highest end of the range because the others would dim it more than I want. 75% seems about right to me. Whether the on/off cycle really boosts growth is debatable but it's worth a shot. Considerably less heat being put off by the sinks now too.
1KTrees
Member
That is about 1.4g/w which is good on that metric but I am looking to maximize 4x4 spaces in output. I think in that case I would need about 640w at 1.4g/w. I see growmau5 did it with that Canopy 10.
Stephenj37826
Well-Known Member
Interesting...... Can you link the study. In this study did they us equal delivered light? I do think a big limiting factor is the plants ability to get nutrients required for photosynthesis replenished as rapidly as they are used in higher ppf situations making me think that the vascular system of the plant is the bottle neck. I've heard certain foilar applications can help replenish these nutrients during the lights on time after the plant seems to be spent. I have a tester who swears by optic foilar. He's sent me pics and after application at 6 hrs into lights on the plants pray to the light once again just like at lights on......
Stephenj37826
Well-Known Member
In a 4X4 tent 600 watts on 4 QBs is all you want promise. Maybe if you spread 6 of them out you will be able to go up to 650 or so but I'm thinking the plants won't stand any more without CO2 which is pretty tough in a tent .
1KTrees
Member
My space is actually a sealed room with flat white walls and I'm toying with co2 now. I'm thinking about switching to vertical and using two 7'x6' walls like ttystikk. Trying to increase my lbs/year.
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BobCajun
Well-Known Member
It's in this patent. I've seen other studies that seemed to show that pulsed light doesn't really boost growth but this patent does look pretty convincing by the tables included. Every time they got a considerably higher yield than with continuous light, meaning 24/7. Guess I'll find out soon enough.
Reading the patent again it appears that they used equal quantities of light whether pulsed or continuous, 50 umol. So when dimmed to a certain duty cycle the pulses would be more intense than the continuous. Say a 50% duty cycle would be twice as intense when on. However, maybe you can get the SAME yield with the same intensity pulsed, if you only go down to say 70-75% duty cycle. At least that what it looks to me like they were doing, not all that clear a description really.
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