Buzzer and dc motor in parallel interference

Thread Starter


Joined Feb 20, 2021
Hi, everyone!

Could someone give a hand on this situation? - I'm using a DC motor (3V - 0.5A) and a 12mm Buzzer(3V) connected in parallel and powered by a lithium battery (3.7V) *using a resistor to drop the voltage to 3V. When I connect everything together in parallel, I get some different noises in the buzzer - I believe that's due to some interference by the motor. What can I do to solve this and have a cleaner sound like when the buzzer is connected in parallel alone with the battery? I also would like to understand why this interference is caused by the motor - if someone could guide me some electronics reference - I'm loving to learn all about circuits by doing!

Audioguru again

Joined Oct 21, 2019
A resistor in series will reduce the voltage a lot when the motor begins running and when the motor is working hard because that is when its current is very high. So of course the voltage changes affect the buzzer's sound.

The buzzer's sound will also be different when the battery is fully charged at 4.2V and when it is almost dead at 3.0V.
Instead of the resistor you need a low dropout voltage regulator that can provide enough current.


Joined Jan 27, 2019
Without more information I can only surmise that motor‘s commutator, which will cause the motor to draw current in intervals, albeit very brief and frequent ones, is causing a voltage drop at a frequency which interferes with the buzzers sound.


Joined Dec 31, 2017
What can I do to solve this and have a cleaner sound like when the buzzer is connected in parallel
Don't connect the buzzer directly in parallel.
Didn't we determine from a previous thread that the motor is rated 3 to 6 volts?
If this is true you don't need to drop the voltage down to run the motor.
Try wiring the buzzer and motor as shown below using noise suppression capacitors across the motor terminals and buzzer.

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Joined Jan 23, 2018
A DC motor is not a constant load, especially a less expensive one. and by "buzzer" I am guessing that actually it is an electronic sounder with some sort of active circuit within. The resistor couples the two of them because the instant voltage across it varies as the current varies, and that voltage then is subtracted from the battery voltage, which also varies with the load. So the sounder voltage is varied by the motor current. Thus the modulated sound.