Sound also plays a major role in many electronic applications. 

A Piezo Buzzer is one of the many ways you can add an audio element to your project.

They generate beeps and tones when a voltage is applied to it and can be found in many applications such as doorbells, children’s toys, musical instruments, smoke alarms etc.

On the flipside of producing sound, is the ability to record or amplify sound. 

Microphones are devices that capture sound waves and convert them into an electrical signal. 

The signal can then be amplified or converted to a digital signal depending on the needs of the application. 

But, can you use a piezo buzzer as a microphone? Yes, a piezo buzzer can be used as a microphone. Normally the piezo buzzer produces a sound when voltage is applied to it. When used in reverse, a sound can cause the piezoelectric disk of the buzzer to oscillate thus producing a voltage at the terminals of the piezo buzzer. This signal can then be amplified or recorded the same way a microphone does.

Note, additional circuitry will be needed to make a microphone using a piezo buzzer. 

What is a piezo buzzer

To better understand how a piezo buzzer can be used as a microphone, let’s take a closer look at how it works.

Below is what a typical buzzer looks like when you buy it. You might have a few, or you might have seen them before.

If we were to open the piezo buzzer and take a look inside, we would find the lower housing, drive circuit, piezoelectric disk and upper housing.

The main attraction of this setup is the Piezoelectric disk. Hence why it is called a piezo buzzer.

The two faces of the piezoelectric disk have wires attached to them and when a voltage is applied to these wires, the disk oscillates.

Oscillation of the disk is what causes sound. 

Varying the frequency of the voltage applied will cause the piezoelectric disk to oscillate at different frequencies hence generating different pitches of sound.

The oscillation of the piezo disk (when a voltage is applied to it) can be visualised as shown in the diagram above. 

How a microphone works

Let’s switch our view to a microphone.

Microphones are used in many different applications from your favourite singer singing on stage, recording audio, podcasts, making a speech to an audience and so much more.

They are a great way of amplifying your voice over great distances without having to shout at the top of your lungs. 

But, it isn’t just good for amplifying audio, they can be used to record it too. 

Audio can be captured by microphone which can then be converted to a digital signal (which is done by a separate circuit). The digital signal can then be stored for later use (like a digital recorder), or modified (like a voice changer). 

If we were to open up the microphone, you would be able to see the circuit as pictured below:

The main components of the microphone are;

• Diaphragm 
• Coil
• Permanent magnet

When you speak into the microphone, sound waves come in contact with the diaphragm causing it to 

oscillate. 

This causes the coil (which is attached to the diaphragm) to oscillate as well. 

The permanent magnet creates a magnetic field and when the coil moves back and forth through this magnetic field an electric current is produced. 

This electric current can then be amplified or recorded as pleased. 

Difference between a piezo buzzer and microphone

Now that we know how each of these devices works we can look at their main differences and then later see how we can use the piezo buzzer as a microphone. 

The inner circuits of both devices are very similar, but they just work in opposite directions. 

A Piezo buzzer is supplied a voltage that causes its diaphragm (in this case a piezoelectric disk) to vibrate which in turn produces sound.

Microphones work the opposite way. 

Sound waves cause the diaphragm to oscillate which then produces a voltage. 

Can a piezo buzzer be used as a microphone?

Now we have what we need to answer the question of whether you can use a piezo buzzer as a microphone.

So, to create a microphone we essentially need to convert sound waves into an electrical signal.

The beauty of the piezoelectric disk is that it has the ability to work in both directions.

When a voltage is applied to it it produces sound.

But, it can also be used to produce voltage when force or pressure is applied to it. 

This is great news for us since sound waves are a form of pressure which can cause the disk to deform and thus produce a voltage. 

However, just talking into the piezoelectric disk is not going to achieve much. You will need to attach it to a dedicated circuit which can amplify the voltage signals (as they are going to be quite weak).

Piezo buzzer microphone circuit

Below is one of the circuits you can use to create a microphone using a piezo buzzer. 

To make the piezo buzzer more effective, remove the piezoelectric disk from the casing so it is bare. This way sound waves won’t be obstructed by the plastic of the housing. 

Is it effective to use a piezo buzzer as a microphone?

So, a piezo buzzer can be used as a microphone. But, how effective it is at capturing sound waves is another story.

The diaphragms in microphones are designed to be sensitive enough to capture sound waves from a variety of distances and angles. 

Piezoelectric disks are less sensitive compared to diaphragms used in microphones, so it might be harder to pick up sound waves.

If you are using the microphone to amplify sound, it might not be too much of a problem, but if you are using it as a voice recorder this might be an issue as recording sound might be a bit harder as not all audio might be captured.

The post Can I use a piezo buzzer as a microphone? appeared first on Electronic Guidebook.

It comes in many different forms which include Mechanical, Electromechanical, and Piezoelectric.

A switch is an electronic component that has the function of allowing and preventing current flow when used in a circuit. 

But, can a buzzer function as a switch in a circuit? A buzzer cannot function as a switch in a circuit. It’s primary function is to produce an audio signal in the form of ‘buzzing’ or ‘beeping’ when a voltage is applied to it. It does not have the ability to open and close a circuit the same way a switch does.

The main function of a buzzer and switch in a circuit

There are plenty of electronic components used daily in circuits. Individually, they have a certain function in the circuit that contributes to the overall functionality of the circuit. 

A switch and buzzer are no different with each having a key function to play in a circuit. 

Understanding what each does will help you understand why a buzzer cannot function as a switch in a circuit. 

What is the main function of a switch in a circuit?

Let us first take a look at the switch. 

Below, is a simple circuit with a load connected to a battery.

In this circuit the battery is continuously supplying the load with power. 

However, at a certain point the battery is going to run out of energy and therefore will no longer be able to supply power to the load. 

Having this sort of setup in the real world is not very applicable. 

You are rarely going to need to have the battery constantly powering a load. 

This is where the switch plays a crucial role. 

An electrical/electronic switch is a component that connects or disconnects the conducting path in an electrical/electronic circuit, either allowing current to flow, or preventing it from flowing.

If we modify the diagram earlier and add a switch, we get the circuit below. The switch can be in two states ; Closed and Open. 

In diagram A, the switch is Open, causing a break in the conducting path, thereby preventing current from flowing through the LED and powering it. 

Diagram B has the switch closed which creates a conducting path and therefore allows current to flow from the battery to the LED. 

So, you can see, the main function of the switch is to either allow or prevent current from flowing in a circuit. 

What is the main function of a buzzer in a circuit?

Having the ability to produce sound in electronics has many different applications. 

The buzzer is an electronic component that has the ability to produce sound when a voltage is applied to it. 

This can be utilised in many applications. 

One of the biggest applications where a buzzer plays a crucial role is a smoke alarm. When you are sleeping your sense of smell and sight are impaired. 

If a fire starts in your home while you are sleeping, you will have no way of knowing. A buzzer provides a way of letting you know a fire has started through sound. 

Other applications include alarm clocks, doorbells, electronic musical instruments, greeting cards, security systems and many more applications. 

There are three different types of buzzers available ; Mechanical, Electromechanical, and Piezoelectric.

So, a buzzer’s main function in a circuit is to provide an audio signal. 

Why a buzzer cannot be used as a switch in a circuit

Now that you know the function of a switch and buzzer in circuit, we can discuss why a buzzer cannot function as a switch in a circuit.

The main function of a switch is to close and open a circuit, thereby allowing and preventing current to flow respectively.

While the buzzer’s main function is to produce sound when a voltage is applied to it. It is primarily an output device that functions to provide an auditory signal which can be utilised in many different applications. 

The buzzer does not have the ability to function as a switch, as it mechanically has no way of connecting and disconnecting the conducting path of a circuit the way a switch does.

What instance would a buzzer function a switch in a circuit?

There is an instance where a buzzer can disconnect the conducting path in a circuit.

This scenario could arise if the buzzer is damaged and causes an open circuit.

An open circuit  occurs when two points in a circuit are physically disconnected thus representing a switch that is ‘open’.

If a buzzer is damaged, there is a possibility that there is a break in circuit within the buzzer thereby causing an open circuit. 

However, this is far from a buzzer functioning as a switch in a circuit. You wouldn’t want to damage your buzzer just to open a circuit to make it ‘function’ like a switch.

Connecting a switch would be the more logical and sensible approach.

What other functions can a buzzer have in a circuit?

While a buzzer cannot function as a switch in a circuit, it does have another function other than just producing sound.

The piezoelectric type of buzzer has the ability to produce a voltage at its terminals when pressure is applied to the disc responsible for producing sound.

This opens a new set of possibilities for the piezoelectric buzzer. 

It can be used in applications where a sudden force or constant pressure needs to be sensed and/or measured. The piezoelectric buzzer can be connected to a microcontroller analog input which can interpret the voltages from the buzzer. 

Applications could include motion detection, door knock sensor, force measurement, pressure measurement, and many more.

What is the most basic circuit of a buzzer and how does it function

While there are many circuit configurations available for the buzzer, the most basic is one with a battery, switch, and buzzer (similar to our circuit at the beginning).

When the switch is closed, the battery energises the coil within the buzzer causing a rapid back and forth movement of a contact inside the buzzer causing a loud buzzing sound.

Opening the switch causes the coil to be de-energised which in turn will stop the buzzer from producing sound. 

The piezoelectric buzzer requires a bit more than just voltage. It requires some sort of oscillator that is capable of producing a sinusoidal type wave. Just connecting it to a DC voltage will cause a click and no buzzing sound. 

A microcontroller can be used to drive a piezoelectric type buzzer.

The post Can a buzzer function as a switch in a circuit? appeared first on Electronic Guidebook.