I can run 6x CXB3590s on a MW 240-1750 at low amps, right?

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flexy123

Well-Known Member
I can dim my driver from 875-1750mA.

My current light bar with 4x CREE at max power (1750mA X 36V) = 252W total, I know this works.

So I am taking the 252W as maximum the driver can handle, with 6 COBs that means I should be able to comfortably run 6 at 40-42W each, so I'd adjust the driver at 1150mA, that will work, right?

I am aware that going higher than that would trigger OV protection/driver or whatever, just wanting to make sure that I CAN in fact run any number of COBs *as long* as I am under ~~250W for the entire load. (I have no need to even go higher than 40W for each COB)

(I need to expand a 4x CREE CXB3590 light bar, making a new fixture with 2x more COBs so I will have 2x3 COBs at LOW amperage. Same driver, 1750mA. This is for vegetables, lower light requirements, I can probably run each COB at the lowest, 875mA even). Still need to do a PPFD calculation
 
sanjuan

sanjuan

Well-Known Member
The driver's "constant current region" spec (71-143V) puts you at the limit already of 4 x 36V = 144V.

A person could design series/parallel circuits to get around this limitation.
 
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flexy123

Well-Known Member
Ah....didn't consider that.

So...I can do 2x light bars (parallel) with 3x COBs in series each??

Woo..that would make the build even easier looking at it...
 
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BadInfluence

Well-Known Member
@Growmau5 explains this very well in one of his videos. Bottom line is that parallel wiring is possible but not advisable. If one of the cobs changes compared to the others which can be caused by heat for example, one of the cobs can burn out and cause a chain reaction which will result in a completely dead lamp. I can't remember exactly how that works but you should better choose the right driver.

As far as i know you can't compare dimming of LEDs with dimming of a classic light bulb. in a light bulb you just reduce the voltage which reduces the heat in the filament and therefore it glows less bright.
LEDs can be dimmed in 2 different ways (don't quote me on this, i have a solid half knowledge) one method is to pulse the energy so that you basically switch it on and off very quickly. I assume that you can also reduce the current to dim LEDs but that's still beyond my knowledge. Still learning. At the moment I'm plannning a LED lamp for my aquarium with 28 Cree LEDs on star pcbs @1400mA which equals around 4W per LED with 2 meanwell drivers. If that is a success the next thing will be a growmau5 style lamp to replace a 400W HPS.
 
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flexy123

Well-Known Member
Yes I am aware of this potential "risk" with parallel wiring. On the plus side, if I were to make such a 2x3 fixture, each COB would run with a very low 875mA, 31,5W which would not cause any heat worth mentioning, I see this with mine when I run them at 875mA, the heatsink stays literally cool.

I am not 100% sure on that, but I think how the MW drivers dim is actually reducing current, in the driver specs it says output current 875maA-1750mA, there is no indication (AFAIK) that it uses pulsing to dim. (Unlike my cheap ebay LED christmas lights dimmer where it's very obvious that it pulses to dim)

So just out of curiosity, let's imagine a "worst case scenario" with a 2x3 COBS fixture where one LED in a bar would fail for whatever reason.

Should one COB in one of the light bars fail, it would essentially disable the ONE 3x bar that has the failed LED since the circuit is broken.
The second of the parallel bars is still connected, driver would then instead of 875mA send the full 1750mA to each COB.
Since this is still well within normal specs, I can't see this doing harm. (One bar outage would still load the driver and the remaining COBs with values well within specs). They're all active cooled, so the full 63 Wattage for each COB should be a non issue, NOT OPTIMAL, but at least it shouldn't destroy all the LEDs.

Correct me if I made a mistake in my thinking...

In terms of PPFD for my area, 6x COBs at 875mA would be PERFECT.
 
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coreywebster

coreywebster

Well-Known Member
I think if you are wiring the cobs in parallel on each bar then if one cob fails just one cob is out and the circuit is still viable for the others on that bar.
Here is the video, around 14mins in Gm talks about parallel wiring
 
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nevergoodenuf

nevergoodenuf

Well-Known Member
I have been running COB's in parallel for a couple years now without any issues. I have also put different temps on the same parallel circuit, no problem. I actually have a few Y's that allow me to add and subtract COBs as I please. As long as you have at least a one COB cushion, I don't see you having any problems. I have only fried 2 eggs and neither was from a parallel circuit. Now if you start to get into the 320w and 600w drivers, I would consider running fuses inline, so each COB has a fuse to prevent cooking.
 
BOBBY_G

BOBBY_G

Well-Known Member
flexy123 said:
Yes I am aware of this potential "risk" with parallel wiring. On the plus side, if I were to make such a 2x3 fixture, each COB would run with a very low 875mA, 31,5W which would not cause any heat worth mentioning, I see this with mine when I run them at 875mA, the heatsink stays literally cool.

I am not 100% sure on that, but I think how the MW drivers dim is actually reducing current, in the driver specs it says output current 875maA-1750mA, there is no indication (AFAIK) that it uses pulsing to dim. (Unlike my cheap ebay LED christmas lights dimmer where it's very obvious that it pulses to dim)

So just out of curiosity, let's imagine a "worst case scenario" with a 2x3 COBS fixture where one LED in a bar would fail for whatever reason.

Should one COB in one of the light bars fail, it would essentially disable the ONE 3x bar that has the failed LED since the circuit is broken.
The second of the parallel bars is still connected, driver would then instead of 875mA send the full 1750mA to each COB.
Since this is still well within normal specs, I can't see this doing harm. (One bar outage would still load the driver and the remaining COBs with values well within specs). They're all active cooled, so the full 63 Wattage for each COB should be a non issue, NOT OPTIMAL, but at least it shouldn't destroy all the LEDs.

Correct me if I made a mistake in my thinking...

In terms of PPFD for my area, 6x COBs at 875mA would be PERFECT.
Click to expand...
so buy a 1050mA driver? it will have the proper voltage you need as opposed to a 1750
 
Forrestfirebuds

Forrestfirebuds

Member
This is the thread ive been looking for. I bought the wrong drivers and have to run my cob lights in parallel if they are to work. I bought the mw hlg 185h-36b instead of the 185h-c1400b. Glad to see someone else wiring in parallel with no problems because some things ive been reading on has had me a little worried.
 
Forrestfirebuds

Forrestfirebuds

Member
nevergoodenuf said:
I have been running COB's in parallel for a couple years now without any issues. I have also put different temps on the same parallel circuit, no problem. I actually have a few Y's that allow me to add and subtract COBs as I please. As long as you have at least a one COB cushion, I don't see you having any problems. I have only fried 2 eggs and neither was from a parallel circuit. Now if you start to get into the 320w and 600w drivers, I would consider running fuses inline, so each COB has a fuse to prevent cooking.
Click to expand...
How many cobs would you run on a meanwell hlg 185h-36b?
 
nevergoodenuf

nevergoodenuf

Well-Known Member
As long as cooling is sufficient, 2 to 20+. I have a bunch of Y connectors and add and subtract COB as I see fit. I you run 2 and a wire comes loose or a COB fries then the other one will also go. If you run 3, cooling it as if you are running 2 ( to protect the rest if one fails) and so on.
 
Forrestfirebuds

Forrestfirebuds

Member
nevergoodenuf said:
As long as cooling is sufficient, 2 to 20+. I have a bunch of Y connectors and add and subtract COB as I see fit. I you run 2 and a wire comes loose or a COB fries then the other one will also go. If you run 3, cooling it as if you are running 2 ( to protect the rest if one fails) and so on.
Click to expand...
Cool. Thanks. Yeah i was putting 4 cobs on each driver and 3 cobs on each heatsink that is 6 inches wide and 40 inches long and these oscillating wall mount fans blowing on the heatsinks. Plis i do have an air conditioning unit to keep temps at about 82 to 82°f
 
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