Out of the blue Flickering cob setup

Growroom Design
#1

Started a week ago.
Does not happen if I have the dimmer at 100%.
Any thoughts? There does not seem to be any issue with strength of the light at full power. Connections all appear solid.

I reached out to rapidled as well for their input.

Here is the setup

6 x CREE CXB3590 COB LED
-6 x Ideal 50-2303CR COB holder
-6 x 140mm pin heatsink
-1 z HLG-480H-C2100B (75W per COB)
-1 x 3’ x 3’ Canopy Substrate with 2 x 34" Canopy Rails, driver bracket and hanging kit
-6 x SurSeal Thermal Pads
-1 x Cased Potentiometer with Knob
-1 x Power cord
-7 x WAGO 221-412 lever nuts
-40 feet of black 18 AWG solid core bulk wire

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#2

Does the flicker become more pronounced or change in character when playing with the potentiometer? Does it seems touchy?
I’ve seen those cause intermittent / similar problems as the wiper contacts gets dirty / don’t make a solid connection.
Other than that, a bit mysterious. Or maybe the driver is having problems?

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#3

All I can say is that the flicker goes away when the dimmer is set to full power.
I bought this new in January and the potentiometer is fully encased in plastic.
But yeah the driver or the potentiometer seem to be the most likely culprits.

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#4

I bought some dimmable LEDs for a light fixture in our house. They were all fine when dimmed except one that would flicker unless it was cranked to 100%.

Maybe there’s a bad bulb in there messing up the circuit? If possible you could try running the lights with different bulbs removed and see if there’s any difference.

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#5

It’s possible I guess… they are pretty high quality cobs. I would have to remove the light to run this test, so it will have to wait. I have visually inspected all the connections

I’m leaning towards the dimmer, as the driver seems to be pushing full power to the lights. I’m also going to test a completely alternate power source see if that makes a difference.

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#6

Ya that’s probably a good idea before dismantling the fixture…if the other driver does the same then I guess its time to look at the bulbs/fixture

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#7

I’m pretty sure it’s your potentiometer. I’ve seen this while adjusting cheaper pots. I like these:

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#8

I meant another wall socket on a different fuse. Unfortunately I don’t really have another driver. Or at least a comparable one. I have a 100w China crappy. Might not be enough power for the test.

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#9

That’s the one I have. This is a rapid led DIY kit.

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#10

How long ago did you get it? Call them up, I bet they will send you a new one.

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#11

Please also keep us posted as to how this goes. I am about to order that same exact setup less the dimmer.

I’m assuming that when these flicker it is all of the cobs at the same time and not intermittent? Reason I ask is I have a fixture that does not have a dimmer and it has been flickering for about three years and still runs. I know it’s the power supply on this one.

I’ve heard nothing but good things about Rapid. Pretty sure this story ends well as well.

Best of luck!

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#12

I already emailed. They do seem very reputable…reason I went with them.

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#13

Flicker is equal on all cobs, or so it appears. It’s also a random flicker not an oscillating one.

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#14

If you have a 50-100k resistor you could try clipping it across the dimming wires and see if it stabilizes. It does sound like a problem with the potentiometer to me too.

My other guess would be thermal shutoff, but that’s not likely since it gets better with full power.

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#15

They have asked me to remove the potentiometer from the system. If the lights function normal then the potentiometer is the issue.
I’ll report back tonight lights out right now.

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#16

Along with lefthandseeds idea:

Here is an photo of a disassembled pot:

image.png1280×720 669 KB

On the right PCB, the black arc is a carbon based “ink” that is screened onto the substrate. This acts as a carbon resistor. A brush that is connected to the inner ring (silver) contacts the carbon and makes for a resistive circuit. When you approach the stops (full-on/off), the brush contacts either a stake (rivet) or a non-resistive interface such as tinned copper (non-carbon). The stops tend to have better electrical performance than the carbon ink.

Gunk, dust, etc tends to build up on the brush over time and the carbon “ink” can eventually be worn down. This leads to a poor electrical connection.

If you have a volt meter, you may be able to measure the voltage drop across the pot to see if it is varying (and causing the flicker in the dimmer circuit). If it’s varying, you’ll know it’s something with the dimmer circuitry (either the dimmer driver or the pot) that is causing the flicker. Then, remove the pot and perform a measurement on the resistance over the adjustment range to see if it acts smooth and linear and doesn’t have noticeable drop-outs.

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#17

I’ll give it a shot. It’s a cased pot and is maybe 3 months old.

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#18

Is it possible on the b version of drivers to wire nut the dimmer wires together to run at full power if you no longer cared about dimming?

Hope that makes sense! Thanks

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#19

I was told to leave it open. Obviously with caps on the bare wire, but an open circuit and the driver should give full power. The potentiometer is an optional item on these drivers

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#20

I’ve had about 3 pots straight from delivery fail in the same way. Should be a cheap af fix

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