A computing system consists of many parts and one very essential component of a computer is the Monitor.

Is a monitor an input or output device?

A monitor is an output device which displays information in the form of text, graphics and video. Information is sent to the monitor from the CPU. This information is sent to the monitor in machine language, which it then converts to a format a human user can interpret.

Difference between input and output devices  

There are inputs, and there are output devices that can be connected to a computer.

So, what is the difference between input and output? Let’s take a look at each of them individually to better understand the differences between them.

But, before we delve into inputs and outputs, we need to quickly cover what encompasses a computer system. 

A computer system consists of a combination of software and hardware as seen below;

• Central Processing Unit (CPU)
• Software (Operating system)
• Hardware (motherboard, graphics card, sound card, etc)
• Communication ports
• Power system 
• Memory
• Inputs 
• Outputs

What is an input device?

A computer as you might know is a machine. Computers communicate in binary (digital), that is 0’s and 1’s, which is also known as machine code. 

At the heart of any computing system is the Central Processing Unit. The CPU acts like our brain. It has the job of receiving, processing, and transmitting information. 

An input device is responsible for gathering information from the outside world and sending (‘inputting’) this information to the CPU which can then process this data as needed. 

Information in the outside world is analog (not 0’s and 1’s). But in order for the CPU to recognize data, it needs to be presented in digital form. Input devices have the task of converting analog information into digital data which the CPU can process. 

The flow of information starts from the outside world, and makes its way inward to the CPU.

Inputs that can be connected to a computer include devices such as;

• Keyboards
• Mice
• Scanners
• Joystick
• Webcam
• Microphone

What is an output device?

While input devices provide information to the CPU, output devices perform the opposite task. The CPU sends information to an output device which will perform a particular task in the physical world.

The job of the output device is to present information to a user in a format which they can interpret. The format can be text, graphics, tactile, audio and video.

For example, a speaker is an output device. It receives information from the CPU (in machine language), and then converts it to audio which you as the user can listen to. 

Other common computer outputs include;

• Monitor
• Printer
• Headphones/ Earphones
• Projector
• Speakers

The flow of information in this scenario starts at the CPU and works its way ‘out’ toward the output. 

Key differences between input and output devices

Is a monitor an input or output device? An in depth look

So, we just learnt about the differences between an input and output device. So, which category does the monitor belong to?

A monitor is an output device. This is because the monitor is a device which has the purpose of providing information to the user. The information is sent to the monitor from the CPU which it then presents in a visual format which includes text, graphics and video. 

The monitor is the primary output device of the computer. Without it we would not know what tasks we are performing. It’s the main way you interact with your computer and gives you instant visual feedback as a result of a task you might perform within the computer. 

Monitors have many features which include;

• Size
• Resolution
• Bandwidth
• Refresh rate
• Dot Pitch
• Interlaced or non-interlaced

With the advancement of technology there are many different types of monitors available as output devices for computers as seen in the list below;

• Cathode Ray Tube (CRT) – used in earlier computers
• Liquid Crystal Display (LCD)
• LED
• OLED
• DLP
• TFT
• Plasma screen
• Touchscreen

Can a monitor be an input device?

A traditional monitor cannot be an input device because it does not have the technological capabilities to do so. However, over the years, technology has advanced and given us new unforeseen opportunities. 

On the previous list of different types of monitor, there is one type which is very common in computing nowadays. That is the touchscreen monitor. This new technology allows the user to interact with the computer by being able to ‘touch the screen’. Before you were limited to interacting with programs using a mouse and a keyboard, however now with touchscreens you do not need a mouse or keyboard.

In this instance, a touch screen monitor is an input and output device.This is because a touch screen monitor sends data to the CPU, as well as receives data from it. 

Traditional monitors are like a one way street, whereas touch screen monitors are like a two way street where information travels in both directions, making it a combination of an input and output.

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There are many different types of inputs and outputs that can be interfaced to a computer which include devices such as monitors, webcams, scanners, mice, and many more. 

Another very common device missing in that list is a Keyboard. 

Is a keyboard an input or output device?

A keyboard is an input device because it takes information from the outside world (in the form of physical keystrokes from the user), and sends it to the central processing unit (CPU). 

Information is ‘inputted’ into the computer via the keyboard and is why it is an input device. 

Difference between input and output devices

There are inputs, and there are output devices that can be connected to a computer.

So, what is the difference between input and output? Let’s take a look at each of them individually to better understand the differences between them.

But, before we delve into inputs and outputs, we need to quickly cover what encompasses a computer system. 

A computer system consists of a combination of software and hardware as seen below;

• Central Processing Unit (CPU)
• Software (Operating system)
• Hardware (motherboard, graphics card, sound card, etc)
• Communication ports
• Power system 
• Memory
• Inputs 
• Outputs

What is an input device?

A computer as you might know is a machine. Computers communicate in binary (digital), that is 0’s and 1’s, which is also known as machine code. 

At the heart of any computing system is the Central Processing Unit. The CPU acts like our brain. It has the job of receiving, processing, and transmitting information. 

An input device is responsible for gathering information from the outside world and sending (‘inputting’) this information to the CPU which can then process this data as needed. 

Information in the outside world is analog (not 0’s and 1’s). But in order for the CPU to recognize data, it needs to be presented in digital form. Input devices have the task of converting analog information into digital data which the CPU can process. 

The flow of information starts from the outside world, and makes its way inward to the CPU.

Inputs that can be connected to a computer include devices such as;

• Keyboards
• Mice
• Scanners
• Joystick
• Webcam
• Microphone

What is an output device?

While input devices provide information to the CPU, output devices perform the opposite task.  The CPU sends information to an output device which will perform a particular task in the physical world.

For example, a monitor is an output device which is responsible for displaying information in a format that a human user can read and interpret. 

Other common computer outputs include;

• Monitor
• Printer
• Headphones/ Earphones
• Projector
• Speakers

The flow of information in this scenario starts at the CPU and works its way ‘out’ toward the output. 

Key differences between input and output devices

Is a keyboard an input or output device? An in depth look

So, we just learnt about the differences between an input and output device. So which category does the keyboard belong to?

A keyboard is an input device. This comes down to the fact that it receives information from the outside world (primarily through human interaction) and sends it to the CPU. For example, when you press down on a key, that information is sent to the processor which can process it accordingly.

The main way users interact with a computing system using a keyboard as an input is by using the keys. Underneath the keys are buttons which when pressed send information to the CPU. 

A keyboard consists of many keys each having their own unique purpose. There are keys for letters, numbers, symbols, and other various functions. 

Nowadays with the advent of touchscreens, a keyboard doesn’t have to be physically present. They can be displayed on the touchscreen itself. The keyboard is displayed on screen when needed and the user simply has to press the buttons on the screen. 

Can a keyboard be an output device?

The keyboard is primarily an input device, however, keyboards do include LEDs which are outputs. These LEDs are used to provide certain statuses to the user. Like when you press the caps-lock key, an LED illuminates to let you know that caps-lock is on. 

However, the keyboard still remains primarily an input device.

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It is capable of converting digital versions of images and text into physical copies by printing it onto paper.

But, is a printer an input or output device?

A printer is an output device. Information (in the form of digital data) is sent to the printer by a host device (such as a computer). This information is then ‘printed’ by the printer onto paper. The main reason that a printer is an output device is that information is sent ‘out’ of the electronic system (I shall explain this in more detail in this article) 

What is input and output device  

To better understand why a printer is an output device, it will help to understand both Inputs and Outputs and see what are the main differences between them.

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. 

In this case, the processor is onboard the computer’s motherboard, which is essentially the brain of the computing system. 

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. This 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 being used as the processing unit. 

However, 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
  • Mouse
  • Keyboard
• 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)
• Weather stations (Temperature and Humidity sensors)

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 or power leaving the system which 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)

Why a printer is an output device and not an input

So, now that we know the roles of both an input as well an output, we can dive into why a printer is an output device.

As we saw in the flow diagram of output devices, information is sent from processor to an output. 

The printer is a device that receives digital information from a host device (like a computer), and then ‘prints’ this information as a physical media on paper, or whatever other surface it is capable of printing on.  

The flow of information starts from inside the processing unit, and makes its way out toward the printer which is the main reason why it is an output device.

How a printer works as an output device

So, we have seen a printer’s main purpose is to convert digital data into human readable information which it then prints out onto paper.

Let’s take a closer look at how the printer works as an output device.

When it comes to the world of printring, there are many different methods used. But, the two most commonly used methods are Inkjet and Laser.

However the process of how a printer creates a physical copy of digital data remains the same.  

Each printer achieves this using a driver or specialized software whose main job is to convert your image or text into a language that the printer can understand. 

Your image or text is then transferred onto paper using a series of dots. These dots are so small that the naked perceives the end product as a solid image of a series of text and not dots.  

While the process is the same across an Inkjet and Laser printer, what separates the two is how these series of dots are transferred onto paper. 

Inkjet

Inkjet printers use a printer head that contains thousands of tiny holes which drop droplets of ink onto paper at printer speed. 

The liquid ink used is either produced coloured dye, or a liquid that contains solid pigments.

Laser

Instead of using liquid dots, laser printers use dots that are made up of toner (fine power of solid particles).

How does a printer get connected as an output to a computer

Connecting a printer to a computer as an output nowadays is very simple. It only requires a couple of wires  to do so.

The type of wires it uses is a Universal Serial Bus (USB) cable and a Power cable. 

USB is a type protocol for connection, communication and power supply, which is specified for cables and connectors.

These cables are used for computers, peripherals and other other computers. 

So, the printer can get connected to a computer and communicate with it using a USB cable.

However, newer printers do not require a USB cable as they are designed and have the capability to connect with a computer using Wi-Fi.

This can be advantageous as the printer does not have to be placed near the computer and can be connected to many host computers all at once.

Where can a printer be used as an output device?

A printer is commonly used as an output device with a computer or a laptop.

But, with the ability of new printers to communicate with host devices using wi-fi, printers can now be used as an output device with many other wi-fi capable devices such as Smartphones and Tablets. 

This means you can now print your favourite meme using your smartphone. 

What are other output devices similar to a printer

A printer is only one of the many output devices that a computer is able to send information to and control. 

There are many other output devices that provide different functionalities that can be connected to a computer.

Below are some of the most common outputs used in conjunction with a computer;

• Monitor
• Speaker
• Headphones
• Lighting
• Projector
• Sound card
• Video card

What is the purpose of printer as an output device in a computer

A Scanner has the job of converting physical media into a digital format.

The printer on the other hand, as we saw previously, has the job of converting digital data into physical media.

With this ability, the printer lends its helping hand to many applications.

Personal – If you need to print form to fill, or a family photo, you will benefit from having a printer at home for personal use. The great thing is that you do not have to buy the most expensive printer out there. Since you won’t be using it all the time, personal use printers are designed for low volume prints while not sacrificing on quality. 

They are also created to be compact and quiet. 

General –  General use printers are great if you need to print a wide variety of prints at a generally high volume and quality is not an issue.

Examples of general use applications include printer invitations for an event, posters for a garage sale and many more. 

Business – Printers designed for business use are capable of printing at different sizes. They are not limited to your standard A4 paper size. 

They are built to handle the high volumes of printing seen in companies while still producing high quality prints. 

The ability to handle these high volumes is thanks to having larger ink cartridges which can carry more ink. 

Below is list of the many other applications that apply to all types printers mentioned above (this is just a small list);

• Images
• Text documents
• Banners
• Invitations
• Pepakura
• Greeting cards
• Photos
• Screen printing
• Art projects 
• Posters
• Forms

What are the features of a printer

When choosing a printer, you need to consider the applications you will be using it for. 

Then accordingly you can decide what features you will require from your printer to best suit those applications.

While print quality and volume are the most obvious things to look at for a printer, there are other features.

Below are some other features to consider for a printer;

• Print speed
• Print quality
• Laser vs Inkjet
• Connectivity (Cable or Wireless) 
• Size
• Support (from the company when things go wrong)
• User interface

Who can use a printer as an output device?

The printer is not restricted to a certain type of person or industry. 

It is beneficial for personal and business use. 

It can be used by anyone who needs to make physical versions of their digital data such as an essay, image, form etc.

It all comes down to your needs and applications.

Can a printer be used as an input device?

No, a printer cannot be used as an input device. 

The printer does not send information to the computer. 

That’s why it cannot be used as an input device.

The post Is a printer an input or output device? appeared first on Electronic Guidebook.

But, E-Mail is now the preferred way of sending attachments such as documents, images, etc. 

Sometimes however, you might need to send a digital copy of a physical document or image.  

This is where a Scanner has lent its helping hand.

A scanner enables you to make copies of documents, images, etc, which then get sent to the computer as a digital file. 

But, is a scanner an input or output device?

A scanner is an input device. The scanner ‘scans’ images, converts it to digital data and then sends it to a computer. The main reason that a scanner is an input device is that the flow of information works its way from the outside world ‘inward’ towards the computer. 

I shall explain in more detail in this article why a scanner is an input device. 

What is input and output device

To better understand why a scanner is an input device, it will help to understand both Inputs and Outputs and see what the main differences between them are.

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. 

In this case, the processor is onboard the computer’s motherboard, which is essentially the brain of the computing system. 

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. This 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 being used as the processing unit. 

However, 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
  • Mouse
  • Keyboard
• 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)
• Weather stations (Temperature and Humidity sensors)

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 or power leaving the system which 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)

Why a scanner is an input device and not an output

So, now we know the roles of an input as well an output device, we can dive into why a scanner is an input device and not an output.

As we saw in the flow diagram of input devices, information is sent from the input to the processor.

The scanner is a device that captures information and sends it to the processor (in this instance a computer). 

It scans an image, then converts it  into digital data which is then sent to a computer for processing. 

The flow of information starts from outside of the processing unit, and makes its way toward the computer as we saw earlier with the flow diagram of input devices. 

How a scanner works as an input device

Let’s take a closer look at how the scanner is able to send information to a computer as an input device.

There are many different types of scanners available. 

The one you are probably most familiar with is a desktop scanner known as a Flatbed scanner. This type of scanner is synonymous with desktop computers. 

Other variety of scanners include;

• Sheet-Fed 
• Hand-Held
• Drum

While there are a variety of scanners, the working principle and purpose for each of them remains the same; which is to analyse an image/document and process it in some way.

If we were to open up the sanner you would find the following parts;

• Charge-coupled device (CCD) array 
• Mirrors
• Scan head
• Glass plate
• Lamp 
• Lens
• Stepper motor
• Belt
• Control circuitry 

The main part of the scanner is the CCD array which is consistent across the different types of scanner. 

The CCD array consists of a  number of tiny light sensitive diodes which convert photons (light) into electrons (electrical charge).

To not go into too much detail, below is a summarized version of what is involved when a document is scanned;

1. Document/Image placed on glass plate
2. Lamp illuminates document
3. Scan head (mirrors, lens, filter and CCD array) moved slowly across length of document with belt which is attached to stepper motor
4. Image of document reflected by a mirror that is angled to a second mirror  (each mirror is curved to to focus image onto a smaller surface)
5. The last mirror reflects the image onto the lens which then focuses the image through a filter onto the CCD array. 

How does a scanner get connected as an input to a computer

Connecting a scanner to a computer as an input  is very simple. It only requires one wire to do so.

The type of wire it uses is a Universal Serial Bus (USB) cable. 

USB is a type protocol for connection, communication and power supply, which is specified for cables and connectors.

These cables are used for computers, peripherals and other other computers. 

So, the scanner can get connected to a computer and communicate with it while also being powered, with one cable!

However, newer scanners do not require  a USB cable as they are designed and have the capability to connect with a computer using Wi-Fi.

This can be advantageous as the scanner does not have to be placed near the computer. 

Where can a scanner be used as an input device?

A scanner is commonly used as an input device to a computer or a laptop.

But, with the ability of new scanners to communicate with host devices using wi-fi, scanners can now be used as an input device with many other wi-fi capable devices such as Smartphones and Tablets. 

What are other input devices similar to a scanner

A scanner is only one of the many input devices that sends data to a computer.

There are many other input devices that provide different types of data to computers through means of  audio, video, and motion

Below are some of the most common inputs used in conjunction with a computer;

• Webcam
• Mouse
• Keyboard
• Digital camera
• Microphone
• Joystick

What is the purpose of scanner as an input device in a computer

The main purpose of a scanner is to create a digital version of a physical document or image that you have.

This feature of the scanner opens up doors to many applications which make it a necessary peripheral when using a computer. 

Long distance communication- As mentioned at the start of this article, fax machines were the standard tool used if you needed to send a document from one place to another. This was how business was done for a long time. 

But, with the emergence of scanners, along with email, the process of sending documents and images was made much easier. 

You could scan multiple documents and images and send them via email to your intended recipient.

Preserving memories – Digital cameras are standard for capturing your memories these days. They can save your photos onto an SD card which you can save onto the cloud so they are safe. 

But, before digital cameras were available, cameras had film which then had to be developed into physical photos.

Physical photos degrade over time, and you also run the risk of losing them or damaging them. 

If you have photos from your past, you can convert them to a digital image and store them on your computer or the cloud which is a much safer option.

Drawing – There are great software programs that allow you to modify and create beautiful digital artwork. 

The two most commonly used programs are Adobe Photoshop and Illustrator. 

Nowadays as an artist, you can take your initial sketches on paper, scan them onto a computer and modify them using the software programs mentioned above. 

This wouldn’t be possible without a scanner. 

Who can use a scanner as an input device?

The scanner is not restricted to a certain type of person or industry. 

It is beneficial for personal and business use. 

It can be used by anyone who needs to make digital copies of existing documents. It all comes down to your needs and applications.

Can a scanner be used as an output device?

No, a scanner cannot be used as an output device. 

The computer does not send information to or control the scanner in any way, but rather receives information from it. 

That’s why it cannot be used as an output device.

The post Is a scanner an input or output device? appeared first on Electronic Guidebook.

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.

Applications of a buzzer as an output device

Below are some common applications where a buzzer is used an output device:

• Alarms
  • Burglar alarms
  • Fire alarms
  • Alarm clocks
• Timers
• Doorbells
• Electronic toys
• Electronic musical instruments

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An LDR (Light Dependent Resistor) is one of those components that has the ability to detect light levels.

But, is an LDR an input or output? The LDR is an input device which is connected to a device capable of processing such as a Microcontroller or Microprocessor. It is an input device because it provides information to the processing device. Information flows from the LDR to the microcontroller/microprocessor. 

Output devices are things the processing device sends information to or controls in one way or another. Devices like motors, Light Emitting Diodes, Speakers etc. 

Input and Outputs

To better understand why an LDR is an input, it will help to understand the basics of Inputs and Outputs. 

Inputs and Outputs are commonly used in embedded systems. The embedded system includes a processing unit (microcontroller or microprocessor), input and outputs.

A computing system is a great example of an embedded system that includes a processing unit, input and outputs. 

The inputs of the computer include the mouse, keyboard, usb drive, headphone jack etc.

Outputs include the screen, printer, speakers, etc.

Input

An input is a device that receives information from the physical world and sends it to the processing system.

In the computer system, the keyboard receives an ‘input’ from the physical world in the form of a button press. Whenever you push a button, information is sent to the processing unit that lets it know what button has been pressed.

The flow of data starts from the outside, and works its way in. 

An input can be a button/switch, or, a sensor. There are a range of sensors available capable of sensing the physical world which range from sensing temperature to light levels (like the LDR) and much more. 

Output

While an input receives information from the outside world and sends it to the processing system, an output works in reverse.

The flow of data starts in the processing unit and data is sent to the output. 

An output is a device that gets controlled by a microcontroller or microprocessor depending on circumstances (or statements) which are determined by program code. 

For example, you might write a piece of code that turns on an LED (light emitting diode) every 10 seconds.

These circumstances can also be influenced by inputs. 

Say, you want to turn on a fan every time it gets hot. A temperature sensor can sense the temperature every time it exceeds a threshold temperature and send this information to the processing unit. The processing unit can then turn on the fan.

Common outputs used in embedded systems include:

• Motors (stepper motors, servos, brushless DC motors)
• Displays (LCDs, OLED’s)
• Pumps
• Actuators

Why the LDR is an input

So, why is the LDR an input? 

The LDR is an input because it provides an embedded system with information it receives from the external world. 

It is a type of resistor whose resistance varies depending on light intensity. Lower intensity light levels generate higher resistances and vice versa.

The information that it outputs is sent to a processing device which will process it accordingly depending on the needs of the application. 

As you can see, the LDR is an input because the flow of information starts from the outside world (this case light) and works its way inward towards the processing unit via the LDR. 

Common configurations of LDR as an Input

There are two typical configurations an LDR is used as an input ; using a Micrcontroller and using an Transistor.

Configuration #1 : Using a Micrcontroller

Since the resistance of LDR varies depending on light intensity, its common configuration as an input is a voltage divider.

The purpose of a voltage divider is to scale down a voltage. When an LDR is used instead of a fixed resistor, the output voltage of the voltage divider varies as the resistance of the LDR changes.

This voltage can be used as input for a microcontroller’s ADC (analog to digital converter). The ADC can take this analog voltage and convert into a digital signal that the microcontroller can process. 

Configuration #2 : Using a transistor

Another common configuration an LDR is used as input is with a transistor and other passive components such as resistors, diodes and capacitors. This configuration does not use  a microcontroller.

A simple circuit (as seen below) uses the LDR as an input to the transistor to turn on an LED (at the output). 

Low light levels (when it’s dark) cause the LDR to increase in resistance, which causes the voltage at the base of the voltage to decrease leaving the transistor off. Due to this, no current can flow through the LED,

When light levels increase, the resistance of the LDR decreases causing a higher voltage at the base of the transistor and thus turning it on. Now a current can flow through the LED turning it on.

Can an LDR directly input to a microcontroller

As you saw above, a microcontroller has ADC inputs capable of converting analog voltages to a digital signal. 

However, it does not have any capabilities of reading resistances and since an LDR changes its resistance, it cannot be directly connected to a microcontroller. 

It will need to be used in a voltage divider configuration as mentioned above. 

Applications where an LDR is used as an input

The LDR is a versatile component used in many applications as an input. It can be found in your home, in many businesses and outside on the streets.

Below are some common LDR applications.

Alarms

The first application where an LDR is used as an input is burglar alarms. These types of alarms tend to be placed at doorways.

A laser is placed on one side of the doorway and its beam aimed at LDR on the other side of the doorway. When the beam is broken (ie. when someone walks past it) the resistance of the LDR changes and an alarm is triggered.

These types of alarms are usually found at storefronts and businesses to indicate to the people working that someone has entered.

Streetlights

Street Lights help illuminate the roads so that we can drive, and walk safely during the night.

The sun rises and sets at different times of the day. So light levels vary accordingly. Having someone manually turn on and off these street lights is very inefficient. 

LDR’s are placed in street lights and help them sense light levels so they can turn on and off automatically without the need of a human operator, thus making them more efficient. 

Solar night lights

You might have some in your garden, or might have seen them in other people’s gardens in your neighbourhood. 

Solar night lights are a great way to add some personality to your front and backyard. Just like the street lights they can also help you navigate your garden safely during the night.

They also have LDR’s that help detect light levels so they automatically turn on when light levels drop, saving you the hassle of having to turn them on manually. 

Using an LDR also helps the solar night light conserve power, as it only has to remain on when necessary. 

Smoke alarms

Yes, you read that right. Smoke alarms also use the LDR as inputs to detect when a fire is present. 

Fires pose a great threat anytime of the day or night, but even more so during the night time when you are sleeping. If a fire starts when you are sleeping you might not be aware of it until it’s too late. 

Having a smoke alarm in your house can be the difference between life and death.

A smoke alarm that uses an LDR works in similar principle to the alarms mentioned earlier. 

An LED shines a beam onto the LDR. When that beam is broken by smoke, an alarm is triggered. 

What does an LDR input into?

If an LDR is used by itself, it is quite redundant. All it is capable of doing is changing its resistance as light levels vary. 

It needs to be used as an input with a device like a microcontroller which can process and make sense of these changes in resistance. 

As you saw earlier the voltage divider is the most common configuration the LDR is found in when used as input to a microcontroller or transistor.

Can an LDR be used as an output?

The LDR’s main function is to react to changes in light levels which means it can only be useful when used as an input in the configurations using a microcontroller or transistor.

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These senses allow us to navigate and make sense (pardon the pun) of the world.

Imagine a world where you couldn’t smell or taste your favourite food, or be able to see where you are walking.

Sensors play a crucial role in an electronic system in the same way our 5 senses play a crucial role in our lives. 

They interpret real world data and send this information to a microcontroller or microprocessor for  processing.

Real world data such as temperature, rotation of a motor, force, pressure, humidity and many more. 

But, are these sensors input or output devices?

Sensors are in fact Input devices. They interpret information from the real world and convert it to a signal that can be processed (by the main processing unit). 

The flow of information starts from outside the electronic system (this case the real world) and works its way toward the main processing unit (microcontroller or microprocessor)  via the sensor. 

I shall cover more detail of the difference between Inputs and Outputs below.

Difference between and Input and Output?

In an electronic system the main processing unit is either a microcontroller or microprocessor, which executes the main program. 

Connected to the main processing unit are inputs and outputs.

To better understand whether a sensor is an Input or an Output, it will help to understand the differences between them.

Input

An input is something that reacts to external changes, and sends this information to the microcontroller for processing. The main objective of an input is sending data to a microcontroller. 

It can be something as simple as pressing a button. 

A button is considered an input because it is responding to a change in state through physical touch (either high to low, or low to high) and sending this information to be processed accordingly. 

Sensors are the most common form of inputs. 

For example, a temperature sensor reacts to changes in temperature and sends this information to the main processing unit to be further dealt with. 

Outputs

Outputs on the other hand work in the opposite direction. 

Rather than sending information to a microcontroller, a microcontroller sends information to the output which responds accordingly.

A Liquid Crystal Display (LCD) is a common output. It has the ability to display information sent to it by the main processing unit. 

Other forms of outputs are motors, speakers, buzzers, LEDs and many more. 

Below is a simple flow diagram of an electronic system with and input and output:

Sensors

So, now that we have established that sensors devices are inputs and not outputs, let’s take a closer look at the Sensor.

As I mentioned earlier, Sensors are input devices that respond and/or detect changes in the environment.

However, a sensor cannot do much by itself. It requires some sort of processing unit, like a microcontroller or microprocessor.

Working Principle

A sensor outputs a voltage depending on how it detects the physical environment.

The minimum and maximum levels of voltage depend on the electronic system as well as the maximum voltage range of  the sensor.

The change in voltage level that it outputs according to the changes in the physical environment depend on its Resolution or Sensitivity.  

So, if the output of a Light Dependent Resistor (LDR) varies by 0.5V for an increase of 1 Lux (light intensity), then its resolution is 0.5V/Lux.

This voltage gets sent to the Microcontroller’s Analog to Digital Converter. As the name suggests, this part of the microcontroller has the job of converting this analog signal into digital values.

Two primary types of Sensors

In the field of electronics, there are two types of sensors; Analog and Digital. 

Analog sensors convert physical data and output them in the form of an analog signal. This analog signal is a range of values depending on the voltages that it is working with.

For example, imagine you have a temperature sensor that has a resolution of 0.1V/Degree.

So, for every degree change you will have an increase or decrease of 0.1V. 

This gives us a nice continuous analog signal waveform. 

Digital sensors on the other hand, are limited to a certain set of possible values (these values being ones and zeros).

Due to this fact, analog sensors are much more precise than their digital counter parts. 

Different types of sensors 

Depending on the application, be sure there will be a sensor available.

Need to detect smoke, there’s a sensor for that.

Need to find the distance between you and an object, there’s a sensor for that. 

You get the point. 

Below are a list of different sensors available depending on your needs:

• Temperature Sensor
• Proximity Sensor
• Accelerometer
• IR Sensor (Infrared Sensor)
• Pressure Sensor
• Light Sensor
• Ultrasonic Sensor
• Smoke, Gas and Alcohol Sensor
• Touch Sensor
• Color Sensor
• Humidity Sensor
• Tilt Sensor
• Flow and Level Sensor

This however, is not an extensive list, but a list of the most common sensors available.

Why use sensors?

But, why use sensors to begin with? What is their real purpose?

We know that sensors can sense changes in the physical world. This benefits us in many applications.

We can all feel the temperature rise and fall, but we cannot accurately tell the precise temperature. 

Sensors however, have the ability to accurately determine the exact temperature. This helps Meteorologists predict weather patterns, so that you can plan whether to take your umbrella or not when heading out on a cloudy day.

Smoke detectors are built with smoke sensors that sound an alarm every time it senses smoke, which means there is an imminent danger of a fire.

They help us stay one step ahead of the game, letting us be proactive rather than reactive.

Since human beings only have 5 senses, electronic sensors enable us to extend our  sensing abilities.

Where are sensors used?

Sensors can be found everywhere from your home, your car, your mobile phone and many other areas and fields.

Here are some of the most common applications :

• Consumer Electronics (mobile phones, gaming systems, Computers etc)
• Automobile
• Aviation
• Medical
• Safety
• Chemical 
• Marine 
• Weather

Again, there are many more applications but these are the most common.

Conclusion

Sensors are devices that help us in daily life.

They help us sense things that we simply would not be able.

While there are many different definitions of a sensor, one thing that is certain is that they are input devices.

It is an input device that provides a signal to a processing unit depending on changes it detects in the real world.

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