Luminous and citizen both have cobs in the 52 volt nominal range. If that helps any. Also, data sheets show the gen 7 vero b at what looks to be just under 50 volts at 900ma. The 3 ish volts per cob isn’t a big deal?
Holy crap… my brain is hurting… 
Really guy’s…
It’s really hurting…
I need to go smoke…
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I am actually building a fixture with three VERO29 B’s, 150 volts is fine, but I’m going to run them at 1.8 amps, so they drop 52 volts each. 900 ma just requires a current sense resistor change. Anything in the 133 to 160 volt range is fine. I just need to calculate the capacitor value so the voltage sags down to 2 volts over the forward voltage total, to get maximum efficiency.
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Good deal! I had just been poking through the vero data sheets for @Venomous, and was looking at the b and c specifically. I figured you had calculated for what you needed, but wasn’t sure how tight the range was.
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The B’s at 50-some volts are good for a fixture with three COBs. The D’s at 37 volts are good for a fixture with four COBs. Both super-cheap drivers are very efficient, like 89-90%. But you have to run them on 110-125 VAC. They don’t work on 240 VAC.
So it depends on how many COBs you want. Three or four is not very granular. I am building a fixture with three 3500 K B’s to add some more light for flowering in my 18 square feet of growing space. I’m also building another fixture with two of the 5000 K C’s for another small space I am reserving for vegetating a mother plant.
Once I get I get a good understanding of everything to do with growing I intend to focus more on lighting. I’m happy with the 4 vero c’s at 1400mA but we all know more light is better (to a point). I’ve always been in to building and working on vehicles so this grow is a whole new ball game. It sure is a life saver having some knowledgeable peeps on the forum to help a brother out in times of need. Keep doing what ya do fellas, you’re making a difference for us uneducated new growers trying to get the hang of their new project. Many thanks @dbrn32
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If and when the time comes, those hlg 185’s are very versatile. You can add cobs and run them more efficiently. Those drivers will each run 4 36v cobs at 50 Watts each at over 50% efficient. Then I think you could grab a single 700ma driver to run all four of your vero c’s at around 50 Watts and get good efficiency boost on them too.
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Vero 29 C’s are rated at over 250 watts maximum, so 50 watts is REALLY conservative. They’re not that bad running at more like 77 watts. I run mine at about 82 watts, just because that was a standard current sense resistor value.
Conservative is where i tend to live with them. Back when I was learning, I tried to cram Watts per $1. They’re almost 10% more efficient at 50 watts than 84. For $25ish a cob I would take that. And it allows me to cheat the heatsink a little if I so choose too.
But the bigger picture there would be more mixing heights of a few 70+ watt cobs with 50 watt cobs.
I wouldn’t put a bunch of 50 watt on one side and 70 watt on the other, unless they could be separately raised or lowered. But I think you could put them on one fixture with some attempt to scatter them both around it. There really is a lot of light from multiple COBs on any part of the plant.
That’s exactly what I meant. If you run grows like you do, it probably wouldn’t be that big of a deal. But if you’re running something tight and they’re all at the same height, you’ll either have your 50 watt cobs higher than you need to or your 70+ cobs at a height where beaching is more likely.
I don’t like running that tight. The very top of the plant is 14 inches from the light but the lower parts suffer a lot from the inverse square law. The Blue Dream plant I’m flowering now is a good compromise: It has about 25 cola sites at the same height. (See my Blue Dream Grow Journal.) The lower parts are completely shaded so inverse square distance is not a factor.
But my clones are going to be SCROGed, to get the same effect and keep them short enough to run inside. Every top should get about the same amount of light. Below the canopy doesn’t matter. I’ll probably do some lollipopping.
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New COB light with three Vero29s and my ultracheap driver. They run at 1.8 amps, 50.7 volts each, so the total power of the COBs is 273.6 watts. Measured power consumption of the whole fixture is 305.5 watts, so my driver circuit is about 89.6% efficient. Bridgelux spec says the COBs run at 160 lumens per watt at this current. Here is a picture of the whole fixture:
Here are pictures of my driver board, top and bottom:
The board supplies 170 VDC to the current limit devices. I used two of the LM317 adjustable voltage regulators in constant-current mode because each is limited to 20 watts and 1,5 amps. So each of them supplies 0.9 amps and everybody stays cool and happy. These regulators cost 58 cents each at Digikey!
Here are the LM317s:
And, yes, I use 1/4" copper under all the hot parts to spread the heat very well into the heat sinks. Transfers heat almost twice as well as aluminum.
@dbrn32 @BIGE @Bogleg @MattyBear @Venomous @nostril @Myfriendis410
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Cool! What’s color temp?
Also wondering what kind of voltage droop if any you’re seeing from start up to temp equalization?
Have not run it long enough yet to get that. These heat sinks are not big enough to run without air flow. I have some air plumbing to do. I have run it for a few minutes and it does warm up slowly but surely. I’m sure over the course of 15 minutes it would get too hot to touch, because my other fixtures did that when the air duct fell off the fan. That triggered the thermal cutoff switch and saved the COBs. (Never trust just duct tape: Always use screws on air ducts too.) With the air flow, they only get up to about 90 F, so I don’t expect much change.
Color temp is 3500 K, to do flowering with my 5000 K veg COBs.
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