Is a buzzer an input or output device?

A buzzer is an electronic device whose main purpose is to provide a ‘buzzing’ sound when a voltage is applied to it.

However, it should not be confused with a speaker, as a speaker is able to play a variety of sounds, whereas a buzzer can play a specific tone depending on the voltage applied to it.

Buzzers have many applications and can find themselves in alarms, electronic toys, timers and many more.

But, is a buzzer an input or output device? The buzzer is mainly used as an output device in an electronic circuit. An output in an electronic system is where power or information leaves the system. In the case of the buzzer, power is leaving it through means of audible sound and is the main reason a buzzer is an output device.

There are instances however, where certain types of buzzers can be used as an input as well. I shall discuss these later in the article.

Deeper look at input and output devices

Electronic systems can be very simple or very complicated.

They can include systems inside of systems.

But, one thing common with every system is that it will have inputs, and outputs.

So, let’s take a closer look at both input and output devices to understand better why a buzzer is an output device, but can also sometimes be used as an input device.

Input devices

An electronic system will usually include a processor at the center of its operation.

This processor can be a Microcontroller or a Microprocessor depending on the needs, and complexity of the application.

It is responsible for ‘processing’ information.

This information can be generated internally by the processor itself, or the information can be received via Inputs.

The reason for being called an input is because information, or power is entering the system which can be best visualised by the diagram below.

An input device’s main job is reacting to changes in the environment or physical responses by a user which could be as simple as a button press.

The processor can then deal with the information as required.

A note to be made is that embedded systems are usually where you would find a Microcontroller or Microprocessor at the processing unit.

An input can also be part of a non-embedded system, which can be void of a microcontroller or microprocessor.

For example, a flashlight is a simple circuit that does not include a processing unit but includes an input like a button.

There are many different types of input devices available that provide different functionalities in different circuit setups.

Below is a list of some of the many;

Buttons
Switches
Sensors
- Temperature
- Humidity
- Light
- Colour
Microphones
Potentiometers
Light Dependent Resistors (LDR’s)

Below are some common applications that use these input devices;

Computing (Mouse, Keyboard, Webcam etc)
Mobile phones (Keypad, Capacitive touch screen)
Automobile (buttons)
Entertainment systems (buttons, switches, potentiometers)

Output devices

So, we have seen one half of an electronic system,where information enters it through means of power and information via physical changes in the environment also known as the Input.

The second half of the system is an Output.

An output can be best described as information of power leaving the system as can be visualised by the diagram below.

Once the information has been processed by the processor, it can then be sent out of the system into the real world via an output device.

An example would be displaying information on an Liquid Crystal Display (LCD).

Just like an input, outputs can be part of non-embedded systems as well.

Going back to the flashlight example, when the button (input) is pressed by the user, a light turns on. The light here is the output of this simple electronic system.

Below is a list of common outputs;

Motors
- Servo
- Stepper
- Vibration
Buzzers
Speakers
Displays
Lighting
- Light Emitting Diodes
- Light Bulbs
- Electroluminescent wire
Printers

Below are some common applications that use these output devices;

Audio systems (Speakers)
Entertainment (Displays)
Computing (Printers)
Interior decorating (LED, Light bulbs)
Mobile phone (Vibration Motors)

What is a buzzer?

If you ever need to add sound to your next project, the buzzer is a great device that will enable you to do so.

The main working principle is that when a voltage is applied to a buzzer, a material within the buzzer oscillates causing a buzzing sound.

Changing the frequency of the buzzer will change the pitch of the sound.

There are three types of buzzer;

Electromechanical
Mechanical
Piezoelectric

The Electromechanical buzzer was the earlier of the three invented in 1831 by Joseph Henry. These were commonly used as doorbells.

The piezoelectric buzzer is the most commonly used today.

Why a buzzer is an output device

So, with the knowledge of what an output is, as well as what a buzzer does, we can see why a buzzer is an output device.

A sound is produced by the buzzer based on events that might be controlled by an input or just internal conditions in the processing unit.

Example of when the buzzer responds to an input, would be a simple doorbell. When the user presses the doorbell button, the buzzer is sounded.

An example of an internal condition is a Timer. When specific software statements are met within the processing unit, the buzzer can be triggered.

Power (in the form of sound) is leaving the system therefore putting the buzzer in the output device category.

Common circuits where a buzzer is used as an output device

There are a couple of circuit configurations when using a buzzer as an output device.

It can either be used in a circuit with a microcontroller, or without a microcontroller.

Below is the circuit of buzzer when used with a microcontroller

The next circuit is a buzzer used in a circuit with a microcontroller.

When a buzzer can be used as an input device 00

While the buzzer is primarily an output device, the piezoelectric type buzzers can also be used as an input.

Inside the piezoelectric buzzer is a piezoelectric transducer disc.

As an output, voltage is applied to the piezoelectric disc which causes the disc to oscillate thereby generating sound.

The piezoelectric disc has a neat trick however.

When a force is applied to the disc, it can generate a small voltage at its terminals, thus now making the buzzer an input device.

It can be connected to a microcontroller which has the ability to interpret these voltages via the Analog to Digital Converter.

This opens up the door to many more applications.

Why would you want to use a buzzer as an input device?

But, there are force sensors available that perform the same function as a buzzer when used as an input device.

So, why would you want to use a buzzer as a force sensor?

The main reason being that buzzers are much cheaper than force sensors. So, being able to take them apart and use the piezoelectric disc is a much better option.