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LED FAQ) Building and DIY
- Thread starter Dion
- Start date
Not when you are running them at 10Watts each. That's 40W per sq ft which is less than many people run HPS at. My rule of thumb is to run HID at 40-50W/sq ft. and LED at 30-40W/sq ft. Now that's not based on super cropping which can give you an even canopy and get efficient LEDs like CXB3590 down to just over 20W/sq ft.
Wiring 80 COBs would be a pain, even at 10 per 100W driver. I wouldn't do it, I would use 20 x CXB3590 running at 40W each. But then again, I don't do commercial sized grows like 4' x 5'.
A single 2' x 2' grow is heaps for personal use, that would be 16 x Chinese 100W COBS running at 12.5W each which works out to 200W if you turn it up full, normally run at about 150W. In the past I would have used a 250W HID for that space and had a lot more shadow. That's the big thing about LEDs, you get rid of the shadow a single HID casts.
Some actual measurements.
https://orchidborealis.blogspot.com.cy/2015/11/diy-chip-on-board-cob-leds.html
Vero 29 4000K running at 42W has a PPFD of 280 at 12"
CXA3070 3000K Z2 bin running at 41W has a PPFD of 250 at 12"
Chinese 100W 3000K running at 41W has a PPFD of 175 at 12"
From another source I have th following measurement:
CXB3590 3500K CD bin running at 48.9W has a PPFD of 365 at 12"
Because the CXB3590 is running at 20% more watts, it's not a great comparison.
I certainly wouldn't run the Chinese COB as high as 41W like the tester did.
So you can see the Chinese COBs are far from useless, it's just that if you have more money you can get better COBs if you want to, but expect to pay 10x the price.
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Depends how even your canopy is, if it's a nice flat SCROG 20W is fine, but if it's an arrangement of different plants at different heights, you will need more power or the lower parts wont be well lit. When everything is even, the lower you can hang your lights, so the lower the power you need to run. It's a matter of trial and error, a normal lux meter helps, it wont tell you PPFD, but it will tell you if the light is bright enough. About 40,000-50,000 lux at the grow tips with a CXB3590 seems to be good, the lower buds need to get at least 20,000 lux or it gets a bit popcorn.
Some people have made LUX -> PPFD conversion tables for popular Cree LEDS at different color temps. I don't have any links, but I remember seeing them around.
50W over 1sqft with a standard scrog where the tops aren't allowed to deviate from the screen other than to cone up and stack above the screen. I've pulled this off with 600W HPS with the glass of a coolhood right ontop of the canopy. Tradeoff with the LEDs COBs now are cost when considering how hard to run them and the number to spread over an array above a canopy.
About 350W of CXB3590 will match a typical 600W HPS.
Here is a shoot out yield video using 1200W HPS vs 1200W LED
https://www.youtube.com/watch?v=IKXEFAhSQoM
Dude, you originally responded to a post by DTOG. While I don't personally know the man, I've seen the pics of his work and he probably clones in a 4' x 5' space! He's not somebody that's growing 12 1' plants in solo cups in his bedroom closet or that grows with CFLS.
You seem to be real good at telling everybody else what they should do, how about posting some pics of your setup and what you've got going on?
Hanging 80 COB's in that space and the associated cluster fuck of wiring and infrastructure is not practical, or reliable for any normal purpose.
Maybe you caught me on a bad night, but anybody that does anything more than dabble in growing will tell you that good equipment that is reliable and doesn't require constant attention is worth every penny. Certainly initial acquisition cost and the ongoing cost of operation is a factor, but I believe your advice is applicable to very few people in this thread.
Dion has created this thread to advance the use of DIY LEDS and from the start he has recommended Cree COBs for a reason
I'm not completely discounting your ideas but what you're proposing has been done many times before - it just may be much better suited in the microgrow forums.
Many of us have been down the cheap EBay road and found it a great way to learn to build lights, but severely lacking for most practical purposes. My initial chinese LED builds were such shit that I never took pics or posted about them. Doesn't take much searching to find all the folks that tried them and then moved on to Cree or Philips COBs.
Dion
Active member
the best par meter is a plant, you put it under the light and observe
you will find 3 possibilities
1) too much light
2)too little light
3) just right-note that just right will be the widest range
How did you go with those? I just picked up some myself as they were dirt cheap and I didn't have any 90cri LEDs to test.
jikko77
Active member
t-slot framing eu
t-slot framing eu
no idea where to post, maybe can be usefull to other EU diy'er looking for a modular frame, similar to the 80/20.
it's sold in italy and looks like is ship world wide. for sure they ship in eu.
http://www.openbuildsitalia.com/
something else to add in whishlist sigh ...
t-slot framing eu
no idea where to post, maybe can be usefull to other EU diy'er looking for a modular frame, similar to the 80/20.
it's sold in italy and looks like is ship world wide. for sure they ship in eu.
http://www.openbuildsitalia.com/
something else to add in whishlist sigh ...
This kind of boost converter is designed to do exactly that:
http://www.ebay.com/itm/DC-DC-boost...ower-supply-250W-10A-LED-Driver-/181940997254
Dion
Active member
Out of an old mini-fridge. There were two. the other I have 2 100 watt chips on it.
I was wondering if someone could tell me what current a CXB3590 should be pulling at 33volts?
The heatsink is warm to touch, but by no means hot, I don't have a way to measure Tj.
The Cree data sheet for the CXB3590 series, only charts down to 33.5v
I have one in parallel with some other Cree LEDs and it's reading 880mA at 33v on my multimeter, it's on a dimmer driver so I have no absolute reference point. I am a bit worried that my multimeter doesn't like the waveform from the dimmer, and I don't have an oscilloscope.
The heatsink is warm to touch, but by no means hot, I don't have a way to measure Tj.
The Cree data sheet for the CXB3590 series, only charts down to 33.5v
I have one in parallel with some other Cree LEDs and it's reading 880mA at 33v on my multimeter, it's on a dimmer driver so I have no absolute reference point. I am a bit worried that my multimeter doesn't like the waveform from the dimmer, and I don't have an oscilloscope.
If I look at the CXB3590 data sheet and extrapolate the lines, it should be 650mA at 33v on the Tc = 55C curve, so 700mA might be right depending on the cooling.
I think the drivers might be using a PWM signal instead of steady DC and making my multimeter vomit the wrong data.
I guess the easiest thing for me to do is plug a bench supply into the COB, set the volts and current to say 30W, measure the light output with a Lux meter, then stick it back into the driver and set the dimmer knob to the same Lux reading.
Dion
Active member
http://pct.cree.com/dt/index.html
unfortunately not much info for volts in the 30 range, however because they way less work with voltage id assume that the current would be almost 0 before it got that low, they r strings in parallel within the cob so for a total voltage has to be divied up between them all,sorry i can't remember now how the dies r set up in a cxb3590, u will have to google it(i think about 40-60 leds in there)
nice work, so they do drop to 30v at 470mA?
why does it matter about the volts? what r u trying to achieve?
