I have a 12V dc power supply/battery supplying a class D audio amplifier, 12V dc linear actuator (controlled by raspberry pi through an h-bridge), LCD screen and LED light strip (Lighting intensity controlled by raspberry pi through an L293D). My problem is that when music is played through the amplifier, the led light flickers with the base of the music and I can see the voltage and current fluctuating on the multimeter. Also, when i start to raise the linear actuator the same thing happens with the lights and the screen glitches. How can i solve this problem such that everything is still connected to the same power source?

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    \$\begingroup\$ Please provide a picture of your complete setup with cables/wires! \$\endgroup\$ Apr 1, 2020 at 14:53
  • \$\begingroup\$ @EdinFifić I added the schematic \$\endgroup\$ Apr 13, 2020 at 21:27

2 Answers 2


It is possible that your power supply is unable to hold the voltage under a higher load, I don't know because you have not specified neither the power supply current/power rating, nor the power of any of the devices connected to it.
Additionally, a picture can help a lot, as it will help us see what you can't see as being problematic with your setup.
Once you give more details (picture and schematic if possible), I will be able to help.

Without knowing more about the setup I would suggest this:
1. Connect each device to the power supply with a separate cable! Don't use the same cable for multiple devices!
2. Your audio amplifier and the h-bridge controlling the actuator could use a larger electrolytic capacitor on each (2200-4700F).
3. Your cable/wire could be too thin and dropping too much voltage under load.
4. You might also need an additional capacitor on the power supply (2200uF-4700uF).

  • \$\begingroup\$ My power supply is 12V/9A. Excuse me for not providing complete description. I tried disconnecting everything and only connecting the amplifier and speakers. (2x50W class D audio amplifier) .. and when music is played at high volume with base I can see the voltage fluctuations on the multimeter. \$\endgroup\$ Apr 1, 2020 at 15:54
  • \$\begingroup\$ What is the thickness/gauge of your wires? Even short wires will have a voltage drop if they're thin. What is the power of your actuator (or the required current)? Can you take a picture of your setup, including a detailed picture of the amplifier (so that the components on its board are visible)? \$\endgroup\$ Apr 1, 2020 at 16:18
  • \$\begingroup\$ I added the schematic. the wires of the motor around 1.5mm, that of LEDs are around 1mm. The amplifier used is this one: electronics.com.bd/… \$\endgroup\$ Apr 13, 2020 at 21:37

How to prevent current and voltage fluctuations for loads connected in parallel to the same power supply?

For high frequency variations, make sure each load has adequate bypass capacitance to handle its ripple and transients.

For low frequency variations, make sure the power supply has adequate output current capability to provide the maximum required current.

If there are long wires between the supply and (some of) the loads, you may prefer a star connection so that two loads don't share the same connection to the supply. Additional bypass capacitance at the load may also be needed in this case. Large diameter wire might be required to achieve adequately low resistance and inductance.

Also be sure that the return (ground) connection from the loads back to the supply is adequate (low resistance and low inductance).

My problem is that when music is played through the amplifier, the led light flickers with the base of the music and I can see the voltage and current fluctuating on the multimeter.

If you're seeing it with your multimeter, it's a very low frequency variation.

The most likely suspects are the supply is not able to supply adequate current for peak loads, or the wiring between the supply and load has too much resistance.

  • \$\begingroup\$ I don't have long wires. The wire from the power supply to the amplifier is around 10cm. LED's wire is 20cm. The longest wire is that of the screen it's around 70cm. Regarding the capacitor, What value do I need and how do I connect it? \$\endgroup\$ Apr 1, 2020 at 15:59

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