If you connect your arduino to a motor you use this schematic:

enter image description here

However, when it comes to buzzers, which also have a coil, no one protects the circuit:

enter image description here

What the hell is going on? Are these just buzzers "coiless"? How can I find the type of buzzer I have?

1 Answer 1


That kind of "buzzer" doesn't have a coil. It is a "Piezo Transducer" and uses a crystal to produce the sound.

When you're using a real speaker and producing sound you are doing it very differently to switching a motor or a relay on and off. You're generating a much smoother waveform and you don't have the sharp "ON-OFF" that causes a collapse of the magnetic field. You're actually gradually reducing the power and then reversing it to remove the magnetic field then apply a new one in the opposite direction (if you have wired it right of course).

Also the currents involved in driving a speaker like that are minuscule compared to switching a relay, especially when driven direct from the Arduino. For louder volumes you will use an amplifier, and that deals with the whole protection within itself since it is designed to drive a speaker.

  • This picture here states that buzzers have a coil 1.bp.blogspot.com/-j-B5fWFwJVo/UQTewNIMC7I/AAAAAAAACzA/… so you are saying that this coil is harmless to arduino?
    – nemewsys
    Jul 8, 2015 at 12:09
  • 1
    That is a specific component within a circuit within a stand-alone buzzer. It is not a coil directly connected to an Arduino. It is part of an oscillator circuit that drives the piezo transducer and thus is irrelevant to the Arduino.
    – Majenko
    Jul 8, 2015 at 12:20

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