I have a problem with LEDs flickering, especially on low brightness.
I have a single 1000W power supply and a lot of LED lights connected to it mostly as recessed lighting, running long strips often running in parallel. As controllers, I use Shelly RGBW2 (and one Zigbee Gledopto).
It works mostly fine, but now when I am connecting additional strips, it seems there is something fishy happening in the whole circuit. When I am dimming some of the strips, the strips start flickering and what’s worse, some other strips start flickering as well, even when they are connected to a different controller device (e.g. one strip in Gledopto and another in Shelly).
It also apparently somehow depends on PWM frequency of the devices. When the frequency is low, it happens much more. I have to set it up to quite high values, but then the minimal brightness is too high. Here is an example of one of the devices where the flickering happens and where I flashed ESPHome over stock Shelly firmware. Flickering happens when I set two first channels to 25% and then I connect 2x2m to other two channels. These two visibly flicker much more when they are set on e.g. 20%, but one of those visibly flickers even on 100% (and the other doesn’t seem to flicker much on 100% for some reason). Also, when I am switching on the second pair of channels while the first pair is on, the first pair visibly brightens up until the second pair gets to 100% and then dims again to the original value . When these flickers, it seems chaotic, not somehow periodical or something. It also happens on different LEDs.
I suspect it’s some kind of voltage instability in the whole power supply circuit. Could this be solved via adding capacitors (have never done this in the past)? Which ones?
Not that I would have that many of them lying around… I will have to order a new one, I guess . Thanks though.
I can see that when I am measuring the voltage on the power supply when having some of the LED strips on, it oscilates between 23.6 and 23.7. How normal it is that there are such oscilations?
no expert but the common factor here sounds like the power supply - can you swap out to test?
So, I tried a different power supply (much weaker, but I switched off most of the other strips), and it does the same thing, maybe even more.
Could it be wiring?
And make sure you use a shared common ground in setups where it is needed.
@WallyR can you tell me what that means, please? The way I wire the controllers (shelly RGBW2 in this case) is that I connect ground to the Shelly directly from the power supply, then connect ground of LED strips to the individual channels (RGBW - in my case those are just LED strips of different whites, e.g. 2700, 3000, 5000 and 6400 K), and then + is going from the supply to the LEDs and the device. Pretty standard and according to the guide, I believe:
Dimming of LEDs is best with a trailing edge dimming.
All my controllers are remote/zigbee - I am in am existing house where I cannot redo the whole wiring. Are you saying it’s impossible to get what I want with the today technology?
Common ground is when you have multiple circuits connected together.
You have that here, but the Shelly should act as a common ground,
When you learn about circuits then you learn that the DC have a voltage, like 12V and then ground will be 0, but that is only true in that circuit.
So when you measure the voltage then you measure it between the 12V line and the Ground and you should get 12V measured.
If you take another 12V circuit and does the same then you would get 12V measured too.
The problem is that you are looking at somewhat isolated circuits and if you have a earth line in your house and use that as a ground value and then measure on the DC lines, then one might be 17V and the other might be 13V.
The trick is that the same Ground lines in the circuits would then measure 5V and 1V, so the difference would be the 12V.
But if you connect the two circuits by wiring one DC line to the other ground then you would not get 12V. You might get more or less, depending on how you do it. That is why a common ground is important.
In your case I think it is more likely that your load might be too high.
Your channels on the Shelly can only handle 45W with 12V and 90W with 24W.
Thanks for the explanation, that’s what I thought, but given what I wrote above, where I wire all LEDs on a single power supply on a single circuit, I should be fine, right?
Thanks for the tip, but no. Nowhere in my setup there is more than 50W per channel and I am on 24V. And single shelly isn’t handling more than 288W. And that is shelly that is under the heaviest load and what’s funny is that it isn’t even the one that flickers.
But it is really not that strange when you see flickering on lines with low load, because the way dimmers work is to cut a bit of the voltage off in a period and the less load the more you need to cut.
Take a look at the pictures here, then you will understand it.
Well, the link seems to be mostly about AC, right? I am on DC and the controllers are using software PWM. I understand it’s limitations, but I am still surprised that it messes everything up so hard, such as how come dimming one of the channels influences a brightness of another channel (or even a separate device)?
Yeah, I know how it works, I am still somewhat surprised it’s not possible to prevent that from happening somehow, e.g. via something like a capacitor or so.
. When these flickers, it seems chaotic, not somehow periodical or something. It also happens on different LEDs.
. Thanks though.
