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I am fairly new to electronics. I was thinking about a simple circuit and was wondering if it would theoretically work or not. Say I wanted to connect a 12V Piezo buzzer to a switch and a large battery (press momentary switch, buzzer buzzes, release and it stops). Say I wanted to use a large battery, like a lead-acid 12V battery found in a car. I realize this is probably a terrible circuit design and much better ones for buzzers already exist, but I want to know why it wouldn't be a good idea. My real question is this: if I have a 12V Piezo buzzer connected across a large battery, is this basically shorting out the battery by connecting the terminals together? Is it bad for the buzzer or the battery? Or would the battery's internal resistance allow this to work?

Edit: The piezo in question in question is a self-driven 12VDC 58mA buzzer.

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  • \$\begingroup\$ You need to describe your buzzer in more detail. Most piezo buzzers do not work this way--they need to be driven using an oscillator, not just connected to power. Otherwise, they will click when connected and disconnected, but otherwise not do anything. Their electrical properties are similar to those of a capacitor. Apparently you (think you) have a different type, but without knowing about your buzzer, it is impossible to answer the question. \$\endgroup\$ – Oleksandr R. Aug 27 '15 at 5:58
  • \$\begingroup\$ Edited for clarification on piezo. \$\endgroup\$ – usinjin Aug 27 '15 at 17:44
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schematic

simulate this circuit – Schematic created using CircuitLab

Try this instead, connecting buzzer directly to battery is bad idea and i would not recommend you do that,the circuit that i have proposed has a 10 k resistance ,i am not sure about its value but it should be safe,when it comes to car batteries they produce a lot of current which is not safe for MCU or any other device so use a BJT with proper ratings to isolate the MCU or any other device

1)If the internal resistance of your buzzer is very small i will cause buzzer to explode as soon as you connect it to battery and battery will remain intact.

2)Batteries internal resistance will also be small so it wont allow your buzzer to survive.

Use V=IR or(I=V/R) lower the value of R more current flows through the load , if you short the battery ideally infinite current flows and melt the wire but if you connect a thick wire i will become very very hot (Disclaimer :Don't try this at home or anywhere on earth)

Hope this helps

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  • \$\begingroup\$ Most piezo have a very high resistence, I don't think it's a problem to run this without the current limiting resistor as most of these are rated for 3-30v though I suspect we could tune the volume this way with a potentiometer in place of the 10k. \$\endgroup\$ – RYS Aug 27 '15 at 5:39
  • \$\begingroup\$ If your are sure about the resistance of buzzer u can short it but its always better to be safe and voltage 3-30v is only voltage rating ,please check the current rating too,if the battery is rated at more current than buzzer ,buzzer will be destroyed regardless of voltage(even at 3v) \$\endgroup\$ – Lokanath Aug 27 '15 at 5:43
  • \$\begingroup\$ The voltage rating of the device is such that the current through it is safe. OP will need to check this rating or measure the impedance of the device, and can take into account Vce of the transistor. \$\endgroup\$ – RYS Aug 27 '15 at 6:06
  • \$\begingroup\$ If it is a 12v buzzer, then there will be no problem connecting it directly to a 12v car battery. \$\endgroup\$ – HandyHowie Aug 27 '15 at 7:24
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    \$\begingroup\$ @usinjin a battery is a voltage source, not a current source, so the current drawn is determined by the load. \$\endgroup\$ – Oleksandr R. Aug 27 '15 at 18:38
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You have basically two kind of piezo buzzers :

  1. Basic ("external drive") piezo buzzers are a simple piezo disc (a plate of piezo material tied to a metal plate), usually mounted in an acoustic resonator. As Oleksandr R. said, it behaves mostly as a capacitor so if you power it with DC, you won't get any current through it and therefore no power (and no sound output). Those work by applying a (fairly large) AC voltage, and they work best if the frequency of the voltages matches the resonance frequency of the piezo disc, typically a few kHz.
  2. "Self drive" piezo buzzers contain the necessary oscillating circuit in addition to the piezo disc. They take DC voltage input, and do the AC conversion at the optimal frequency before feeding that to the piezo disc. The "12V" you mention seems to indicate that it is this type you have.

In both cases, if it's a "12V" piezo, I don't see any reason why you souldn't plug it to a 12V voltage source. If it's the first type you'll hear a tiny "click" (the AC transient as you plug the DC) then nothing ; if it's the self driven type you'll hear it sound loud and clear.

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  • \$\begingroup\$ I'd call the first type a "piezo transducer", rather than a buzzer. \$\endgroup\$ – Peter Bennett Aug 27 '15 at 16:20

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