Let's talk DIY lights


Yeah, my inspiration was when I realized a COB is not just a light source. It’s a calibrated, broad-spectrum light source. You can use it to calibrate other measurement equipment for measuring other light sources. As soon as you add something that can tell you the intensity, then you can graph your spectrum in lux (or whatever you like) instead of relative intensities.


This is where I think I feel there is an issue with this measuring technique. I wouldn’t say you’re measuring light intensity, not towards the plant anyway. I would say that relative intensity is all you’re measuring. One wavelength vs the rest that you filter for. Which by definition is relative intensity correct? I’m not catching where the transition from photometric energy to radiometric energy comes in?


By relative intensity I was referring to the amount of energy in the spectrum at each band of wavelengths. The graph has percentages along the left axis. I’m not really concerned with the energy of blue photons versus the energy of red photons. I think this tool is much too rough to get into that.

By the way, I was looking at the Cree XP-E datasheet and I see the Relative Flux vs. Current graph for the Photo Red LED shows almost a straight line. (As opposed to the non-linear blues and green.) It goes straight right out to 1000 ma. So as long as you keep it cool, is there any reason to run these at reduced current? I don’t see anything in the datasheet about reliability at different currents and shortened life.


The photo red he? I have a handful here but never got around to doing anything with them, but my understanding is that guys are running them at like 700ma. Probably for the reason you stated, must not be a big enough difference and typical next size up for meanwell is 1050ma.


It really is a very straight line, so the difference between 1000 and 700 would be 1000/700 times as much light. You can turn that Mean Well down to 1000 ma, right?


Most of them


I know that photo red he is good, someone had it listed somewhere at over 4 umol/joule. The one thing I always caution with the cree’s is that they’re pretty liberal with their charts. They’re usually all binned at 25c which is a little unrealistic. And they’ll have some tc vs current and ambient temp charts you have to kind of lay over the flux charts and see where you’re at.

As opposed to bridgelux which will generally give you some 50c and 85c data that’s a little more realistic.


They do have a power graph that shows how you have to derate them at different temperatures. If you can keep them down around 50 C, they run at full power. I always plan to keep parts cool.

But we need to keep in mind that different color LEDs are different semiconductor devices. They can have very different behavior at temps and currents. White COBs are all essentially just blue LEDs stimulating different mixes of phosphors, so they all suffer from high temps and give you more lumens/watt if you run them at low current.

One thing I like about the Photo Reds is that the 660 nm line is perfect for chlorophyll synthesis.


Yep, I agree.

@Onlythebest79 should have some of them going here before too long.


Yes sir getting heat sinks cut Friday and will try and get installed this weekend


Out of likes, but keep me posted!


Question for you: Using the 1 1/2" X 6" tubing in 2’ lengths screwed together, how many strips could I mount per tube? 2? 3? I’m thinking of building 3 units to cover a 4’ X 6’ space and doing it in thirds makes the most sense.

Any suggestions?



I’ll tag @dbrn32 and if you ask him or explain to him he’ll know more than I can tell you and I don’t want to tell you wrong.


If you have 6” of width per tube you could mount up to 6 strips per tube. The strips are about 20mm wide if I remember, if I’m off it’s not by much. They’re definitely less than an inch wide. But I would think that would be overkill. Three per 6” piece is probably on the upper end of good in my opinion. You have room to fudge it one way or the other if you need to squeeze an extra strip in or take one away to fit drivers properly.

I think I said one of those hlg-185’s would fit 9 of the 560mm strips very well. So if you put three pieces of tubing together and three strips on each piece of tubing, you could run that from a single driver for about 200 Watts. And then you’re saying you’d like three different fixtures like that?

If I misunderstood please say so. Just trying to make sure we’re on the same page.


Hey will I need like some insulation tape or something to put between the heatsink and aluminum frame or is it ok to lay the heatsink on the frame bare?

Going to Lowe’s to get a metal cutting saw and tape if I need it


They sent a coverd driver right? Should be insulated.


That about sums it up. I think I’d like to target around 300 watts per fixture which should give me good coverage per 2’ X 4’ fixture. That would give me 900 watts over 24 square feet.


I can also run it the other way if it means a more efficient setup in other words use 44" strips and do two feet of them for 300 watts.


getting to 300 Watts on a single driver is tough with them. The voltage on connectors is limited to 300 volts. Let me see if I can play with the numbers some and see how to best get there.

Excuse my quick crude drawing, limited tools in the truck lol. But this is what you’re looking to do at around 300 Watts per fixture?


Yes, or use the 44" ones if that is more efficient and cut my tubing to 48". Basically right angles.

Even maybe run 2 drivers?