Big or small LED light fixtures?

[Potastica]

Well I have been doing a little tinkering with these cheap 3 watt LEDs and I can say they work...well for the most part things turn out rather nicely...great for budget grows...lol
After looking into buying pre-built units I just couldn't figure out which to buy that suited my needs the best...not into spending $ just to find out its not right and left to buy more...anyways rambling...lol
My question is why are all these lights so compact, if you will, they seem to put everything into a small nice package that lights a fair amount of footage space and generally produce a good amount of heat.
So my question is...before I pull the rest of my hair out or spend a bunch of $ on already tested & failed ideas someone has already done...lol...why not spread the LEDS further away from each other and use a slightly larger area ?
I have found putting the 3W LEDs about 2"-2.5" apart and using 5 rows in 1 'panel' (50x3W LEDs)...takes min 9"-11" x 19"-23.5' and I can keep them fairly cool with just 2 80mm pc box fans...see pics....cost is about $60 I think. (panel has LEDs missing...test panel I steal parts from now...lol), but shows whats I'm referring to...sheet is 12" x 24" and its 6 wires I run about 6' to the driver box which can hold up to 20 drivers, but i run 15...150 LEDs per box seems to work ok, just a simple exhaust fan to remove extra heat is used...more in another thread some day maybe...lol
So why are they made so small when a larger light is needed...because when we join them up all we do is create more heat, burn plants, have to move the light further away from the plant takes up height room/area and so on and so on.
Just wondering what you all think.

 

[Old Salt]

My first guess is economics. It's cheaper to produce and ship a more compact item. Another possibility is resistance from the community to larger lighting fixtures. HID lighting is generally more compact. I don't subscribe to either of these. My gut feeling was to spread the light over the the entire floor area of the tent, so that's what I built. Now I'm catching up with the math to prove it...

Eight COB DIY Grow Light for 2' X 4' (60cm X 120cm)Tent ​

 

[farside05]

I think @Old Salt is probably right. Compact is easier/less costly to ship and takes up less space in the warehouse. Quantum Boards are very popular but LED strips are basically like cut apart Quantum Boards that let you space things out more, dissapating heat and spreading light more evenly across your footprint. Just like Salt, I decided to build mine to cover my entire area. I'd hate to have to ship a 24"x24" fixture (for a 32"x32" tent). I'm sure it would be costly.

IMG_20180611_175321.jpg

• farside05
• Jun 11, 2018

IMG_20180611_181843.jpg

• farside05
• Jun 11, 2018

 

[Potastica]

Yes, I agree with the shipping problem being 1, but just doesn't make sense to me to buy these little furnaces then have to buy fans, a/c, etc to fix heat problems...kinda reminds me of pharma...1 pill fixes another pills problems and before you know it your shelling out $ hand over fist and you have a handful of pills to tend to daily....lol
I have looked in to and done some research on these QB's over the past few days...they do seem to be a much better product. They are fairly compact (easy to ship anyways) and modular...wondering about heat on them tho. Has anyone done heat reading on them in various wattage setting and heights...my next part of research to do on them.
I find it odd different kit manufacturers use different drivers and get same results and some are really pushing the boards limits...would this not reduce the life span? Like some run 54V @ 1.5A vs 48V @ 2.70A...whats the better option ?
I have not looked much in to the strips yet, but the last time I found them very pricey...will be looking in to them again very soon also...thanks for the reminder...wanted to use them long ago,but price stopped me.
I started researching about 3-4 years ago when I first got interested in growing for myself and wanted a ball park of what it was going to cost me...went offline for awhile...now there is mini tents and all this new tech...wish I knew about a lot of this stuff back then...oh well.
Thanks for replies aswell

 

[Old Salt]

Given two fixtures, each with the same drivers, and same LEDs, but different sizes, both will radiate the same amount of heat. The larger fixture will run cooler, as the heat is dispersed over a larger area.

 

[Potastica]

Given two fixtures, each with the same drivers, and same LEDs, but different sizes, both will radiate the same amount of heat. The larger fixture will run cooler, as the heat is dispersed over a larger area.

Was going in a little different direction, but I do understand a bigger surface will take longer to heat up and it will also be cooler when same LEDs and driver used.
Most QBs have variable wattage pot on them so we will just go with that since its prob easiest to use as is.
Divide up the variable wattage pot into say 11 positions...0 to 10
What is the temp of the light in each setting of 1 - 10...0 being off in this case, but still need the value for reference.
eg:
0 the room/tent with nothing running is 75
1 its 77.
2 its 82.
3 its 85...and so on up to full (10) where temp is 120.
Now thats just random numbers, I'm sure are not true, but I'm curious about the temperature levels they produce because they don't use fans on them.

 

[Old Salt]

I have a six COB blurple fixture that draws 315W from the wall. The power supplies in the fan are only 85% efficient. The temperature in the room with the tent is 22°C (71.6°F) with a humidity of 41%. Air is drawn from the room for the tent, and exhausted elsewhere. The flow is about 200 CFM or 5.7 cu meters per min. The tent is 2' X 4' X 7' (56 cu ft) or 60cm X 120cm X 210cm (1.5 cu meters). The light has been on for six hours. The temperature in the tent is 31°C (87.8°F) with a humidity of 31%. There is one fan inside the tent drawing less than 10W from the wall.

Your results will vary depending on the efficiency of the light and its drivers, the airflow through the tent, the temperature / humidity of the incoming air, and the humidity inside the tent.

Fans built into a fixture add to the heat inside the tent. They are there to cool the fixture. Fixtures without fans are passively cooled. The surface area of the LED mounts is large enough to keep the temperature of the LEDs within operating tolerances.

My passively cooled DIY light is a bit extreme in this regard:

Eight COB 16W - 530W DIY Grow Light​

This setup is to test the output of the fixture. I'm not sure what it will do as far as heat is concerned yet. I'll know by this time next year as summer is coming, and I have no air conditioning.

 

[Potastica]

I give up....

 

[Old Salt]

I give up....

There are too many variables to say with any degree of accuracy what will happen. Perhaps someone with a QB, or other LED will chime in with their experience. Sorry I couldn't be more helpful.

 

[Potastica]

No its simple...put the dam light in a tent and measure the temp...NOTHING ELSE.
But nevermind I'm not speaking english or something so I'm gone...l8r y'all and best wishes on your grows...................

 

[sativuhhh]

I agreed and got bigger qb panels that space things out really nicely over the little 288 diode boards.