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LED strip ground loop?

ElectroNoob69

Oct 3, 2022
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I have an LED light strip ( WS2812 ) that I control via a MEGA32U4. The Microcontroller is connected via USB to my PC and receives data to change LED colors accordingly. Everything works fine except that I have a humming noise on my PC headset as soon as the Microcontroller is connected and the LEDs are turned on.

Basically I have the setup shown in the picture below. I suspect the source of the problem is that the Microcontroller is connected to ground of the power supply yet it is also connected to power and ground of the USB port.



r/led - LED strip ground loop?
I only know basic electronics, so please help me solve this issue. Is this a ground loop issue? Is this what you need an optocoupler for?

Thank you in advance
 

Harald Kapp

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Nov 17, 2011
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I suspect the source of the problem is that the Microcontroller is connected to ground of the power supply yet it is also connected to power and ground of the USB port.
That common GND connection is necessary.
Is this a ground loop issue?
Potentially. Easy to identify if you disconnect the power supply for the LEDs completely.
Is this what you need an optocoupler for?
Yes and no.
An optocoupleer could isolate your circuit from the PC, but it is not trivial to set up a USB connection via optocoupler.
You could build a USB isolator using eg. one of the chips offered here. Or buy a USB isolator module as offered e.g here. Btw: These do not use optocouplers but use magnetic coupling for data transfer. The effect is the same.
Another option is a better power supply for the LEDs. The one you use may create EMC (noise) that feeds back to your PC.
 

Keonte45

Aug 29, 2022
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It is possible that the humming noise you are hearing is caused by a ground loop. A ground loop occurs when there is more than one path for electrical current to return to the ground, creating a loop. This can cause electrical noise and interference, which can manifest as humming or buzzing sounds.

One way to eliminate a ground loop is to use an optocoupler, which is a device that uses an infrared LED to optically isolate the connection between the microcontroller and the LED strip. This can prevent the electrical noise and interference caused by the ground loop from reaching the microcontroller and being transmitted to your computer through the USB connection.

Another solution could be to use a USB isolation transformer, which can also isolate the USB connection from the electrical noise and interference.

It is also worth checking to make sure that the power supply for the LED strip is properly grounded and that the ground connection is not being shared with any other electrical devices that may be causing interference.

I hope this helps! Let me know if you have any further questions.
 

Bluejets

Oct 5, 2014
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External birds nest wiring would be the first point to consider.
 
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