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I wanted to do some DIY under cabinet LED lighting with RGBWW strips. These ones to be exact: https://www.amazon.com/dp/B0B5SLM235?ref=ppx_yo2ov_dt_b_product_details&th=1

I am using an arduino and this wiring schematic to control the lights

enter image description here

Instead of +12V and RGB as in the image, I have +24V CW RGB WW. I have two strip sections wired in parallel to the arduino. One section has 3 separate strips that are connect through CAT5e wire and the other section is just a single strip. I have it configured this way because the outlet i want to power the strips and arduino with is in the middle of the kitchen, not at one end or the other.

enter image description here

When I plug in the left section, it all works fine. But when I also plug in the right section, everything blinks once and doesn't do anything. When I lower the analog write value from a max of 255 to 150ish everything works fine. I am wondering why this is occurring and if it can be fixed so I can use max brightness. The power supply I'm using is one that came with the lights and that I cut open to power the LEDs and the Arduino (using a buck converter to 5v). The power supply is 24V and 1 amp. I suspect that its not providing enough current to the LED for all the strips but I don't see how that would make sense if I am using the provided power adapter. Any throughts?

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    This should probably be in the Electronics stack exchange. You will also get better answers if you provide an actual schematic and designed current loads.
    – KMJ
    Commented Jun 14, 2023 at 4:33
  • Does the right section work by itself? If each section works separately, but not together, you might have exceeded a current limit, e.g. a polyfuse on the arduino (if powering through that) or the overload protection in your power supply (which is not shown). Be aware that if you have more than maybe 500mA of lighting current, you should try to make sure it flows around the arduino and not through it. Commented Jun 14, 2023 at 11:37
  • A picture labelled "FET N" doesn't tell us what the actual specs on the drive transistors are. That could matter. The current at the amazon link is described as 1A, but it's not clear what operating mode that's in but 100 lumens per Watt would be reasonable for white mode. You may need to supply more than 1A per strip, or at least >1A for the whole lot. Also double-check your wiring, in case you're shorting something when you plug in both strips at once
    – Chris H
    Commented Jun 14, 2023 at 15:23
  • ... but (only with the additional details) this would make more sense at electronics.se than here
    – Chris H
    Commented Jun 14, 2023 at 15:25

2 Answers 2

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If I had to guess, something is not right with the wiring / voltage.
Why am I making a broad statement about "wiring / voltage"? Because I don't quite understand your different set ups and the resulting voltages.

It seems you're driving multiple 12V LED strips with 24V. This can be fine, if your wiring is set up for every strip to get 12V. I personally drive two 12V fans wired in series using a 24V power supply.

When I plug in the left section, it all works fine.

Here your wiring seems ok-ish, resulting in the correct voltage. At least it's within bounds, because 24V / 3 is 8V, which although not matching the specified 12V might still be close enough. Note that if the three strips on the left are wired in series they only get 1/3 of the voltage. Think of voltage as difference between two points: Those three LED strips connected in series split the difference between them. If you connect them in parallel each will see the full difference between the connection points.

when I also plug in the right section, everything blinks once and doesn't do anything.

The right section seems to either

  • get 24V, overheat and temporarily drop out (if so, be grateful, if the LED strip still works),
  • add the drop to overflow the bucket, i.e. take too much amperes, so the voltage drops (remember it might already be as low as 8V, depending on wiring of the left side)
  • cause a short (if so, be grateful, if your power supply still works)

taking the rest of the circuit with it.

My guess is on the first or second option, because miraculously

When I lower the analog write value from a max of 255 to 150ish everything works fine.

150ish/255th seems to be close enough to 1/2 and 1/2 of 24V is 12V, which is the correct voltage for a single LED strip. Yes, I am aware that you're using PWM to switch on/off the full 24V, however real circuits do have continuous rise/drop of voltage and so there's the correct voltage some of the time. Alternatively, think of it flickering and going out just to come back up with the next PWM cycle. If it flickers fast enough, your eyes won't notice.

Have you perhaps wired the right LED strip so that it is connected as a single LED strip?

The power supply is 24V and 1 amp. I suspect that its not providing enough current to the LED for all the strips but I don't see how that would make sense if I am using the provided power adapter.

This totally makes sense: It's the power supply for up to 4 LED strips, not 4 LED strips (one of which getting 100% over-voltage) plus a buck converter (introducing unknown losses) that powers an Arduino. Which is why I list this as above option 2.

You could try to connect two parallel pairs of two LED strips in series. If my first guess is right, this should solve the issue. If it doesn't, it's probably option 2. Even for option 2, not over-volting the right LED strip may help to stabilize the power supply.

Alternatively, measure the voltage with a multimeter. Yes, the reading may be awkward, because you actually have drops/rises but most multimeter will read some value that is close to the average. No fancy oscilloscope needed, especially because a PWM of 255 is always on.

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  • In the link, the strip has no voltage or current rating, but is supplied with 24v supply. Whats us still unclear is if the strip has been cut into 4 sections or there are 4 strips. But you are right, its overloading. And its never going to work correctly. The left is going to be dimmer than the right Commented Jun 14, 2023 at 20:54
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You'r overloading the power supply.

It is "crowbar"-ing. I.e. shutting off to protect itself.

That's it. Mathematically calculate your current load based on LED strip specs and length, and make sure the power supply is up to snuff. My "general rule of thumb" is 20mA per cut section per channel, and you have 5 channels there: R, G, B, warm and cold white. But your strip may vary.

24W power supply seems awfully light for a 5m RGB strip let alone 10m RGBWW. Check the labeling and instructions and make sure they even allow running it at full power.

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