Output of LM35 analog or digital?

The output of a LM35 is analog as it provides a continuous output signal that varies in value over time.. The output of the LM35 is an analog voltage that is linearly proportional to the centigrade temperature. The LM35 is able to detect temperatures that start as low as −55°C and go up to temperatures as high as 150°C with a 0.5°C accuracy (when operated at optimal temperatures). 

Why is the output signal of the LM35 analog and not digital?

So why is the output of the LM35 analog and not digital? To better understand this we need to learn about analog and digital signals. When it comes to electrical and electronic signals, they are split into two major categories; Analog and Digital. 

An analog signal is represented by a continuous stream of data that sits within minimum and maximum values. The analog signal can be any value within this range. How much it changes is determined by its resolution. For example, an analog signal could be current that has a minimum value of 0A, and a maximum value of 10A. The value of current can anything within this range (for example 5.1A). 

A digital signal on the other hand is represented by discrete values of data. Digital signals can only have two values which are either 0V (GND), or Vcc (the value of the supply voltage). A binary value of 0 is used to represent 0V, and a binary of 1 is used to represent the supply voltage. 

A LM35 output is analog because the signal (voltage) is presented in a continuous form and not discrete. It has a minimum value, and a maximum where the voltage can be any value within that range. 

LM35 output analog voltage

The analog signal provided at the output of the LM35 changes at a  linear scale factor of +10mV/°C. This information tells us that for 1°C increase in temperature, the voltage at the output of the LM35 increases by 10mV. If the temperature decreases by 1°C, the voltage at the output decreases by 10mV.  To acquire the temperature reading, you take the reading at the output of the LM35 and divide it by 10mV. Note, the voltages will need to be in milli-volts. 

For example, if we read a voltage value of 1.25V at the output, this first needs to be converted to a millivolt reading (which is easily done by multiplying it by 1000). This then gives a value of 1250mV. Then we divide this value by 10mV which gives us a temperature reading of 125°C. 

Negative temperatures will yield negative voltages at the output (as long as they’re within the sensing range of the LM35). If the sensor is reading -100mV at its output, this tells us the temperature is -10°C. Follow the same convention above to acquire negative temperatures.

What is the range of the output of a LM35?

The LM35 has an output that ranges from -55°C to 150°C. However, the range at the output is determined by how it is configured in a circuit. There are two circuit configurations for a LM35 which include; basic and full-range.

LM35 basic output configuration

When the LM35 is connected in the basic configuration, its output is limited between 2°C and 150°C. Below is the circuit connection of the LM35 in its basic setup.

LM35 full-range output configuration

Connecting the LM35 in its full-range configuration allows it to detect temperatures that range from -55°C to 150°C (its full capability). The full-range setup for the LM35 can be seen below. 

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Sensors come in many shapes, sizes, and functionalities. If you ever needed to measure force, a Piezoelectric Sensor is the perfect sensor for the job. This sensor works based on the piezoelectric effect which measures changes in force, pressure, or acceleration by converting it to an electrical charge. 

They are very sensitive in nature, and are also quite small making them perfect for many applications where force, pressure and acceleration needs to be measured. 

Some of these applications include;

• Musical greeting cards
• Electronic musical instruments (Electronic Drumkit)
• Guitar pickups
• Alarm clocks
• Automotive car key fobs
• Robotics
• Wearable arts

What are the different types of piezoelectric sensor

There are many different types of piezoelectric sensor which include;

• Piezoelectric Force sensor
• Piezoelectric Pressure sensor
• Piezoelectric Acceleration sensor
• Piezoelectric Polymer pressure sensor

Piezoelectric sensor type #1: Piezoelectric Force and Pressure sensor

The Piezoelectric force and pressure sensor have a similar working principle and construction. These types of sensor measure force and pressure by using piezoelectric elements which are usually quartz crystals. By using quartz crystals as the piezoelectric element, this type of sensor gains high rigidity, a wide measurement range, has high linearity and stability. 

An electric charge (voltage) is generated across the crystals when the piezoelectric sensor is subject to a force or pressure. The force can be a physical touch, or changes in pressure which do necessarily require physical contact with the sensor (i.e, changes in pressure within liquid and gas)

Piezoelectric sensor type #2 Piezoelectric Acceleration Sensor

The next type of piezoelectric sensor on the list is the Piezoelectric Acceleration Sensor, also known as Piezoelectric accelerometers. This variation is often used to measure vibration. There are many vibration sensors available, however, the piezoelectric acceleration sensor offers better all round characteristics such as a wide frequency and dynamic ranges, while being robust and having a long lifespan.

Piezoelectric acceleration sensors achieve their longevity and robustness thanks to no moving parts. They are also self-generating which means they do not require a power supply. Piezoelectric acceleration sensors are available in two variations; Compression and Shear. 

The compression type exerts a compressive force of the piezoelectric element, while the shear type exerts a shear force. 

Piezoelectric sensor type #3 Piezoelectric Polymer Pressure Sensor

Last up is the Piezoelectric Polymer Pressure Sensor. As the name suggests, this type of piezoelectric has the job of detecting changes in pressure. However, unlike the previous piezoelectric pressure sensor (which uses quartz crystals), it measures pressure using Nanofiber Membranes woven using an electrospinning technique which gives them great mechanical and thermal properties. They too are self powered. 

The construction of piezoelectric polymer pressure sensors are lightweight and offer high mechanical flexibility. This makes them a great option for stretchable electronic devices. They are found in many applications which require these unique characteristics from a pressure sensor which include robotics, healthcare, and communication devices to name a few. 

Choosing the right type of piezoelectric sensor

Each type of piezoelectric sensor that we have just seen has its own unique characteristics making them suitable for a particular application. Choosing the right type of piezoelectric sensor comes down to the needs of the application. For example, there are two types of pressure sensor (crystal and polymer). However, if your application requires stretching and movement (like wearable arts), a piezoelectric polymer pressure sensor is the best option as it has better mechanical flexibility.

The post 4 common types of piezoelectric sensor appeared first on Electronic Guidebook.

 However, flex sensors can be quite expensive and can be damaged easily. 

Alternative for a flex sensor

While there isn’t a particular sensor that is available on the market as a direct alternative of the flex sensor (as well as being cheaper), there are many ways to create your own that will be able to mimic the functionality of the flex sensor. This way you can save money as well as learn new ways to create a flex sensor.

One cheap and readily available component that can be used to recreate a flex sensor is a potentiometer. A potentiometer is a three terminal resistor whose resistance can be varied by turning a knob. 

Another alternative is to use materials that you will have available in your home. Materials such as paper, tin foil/aluminium, velostat plastic bags, and masking tape. 

How to make a flex sensor at home

Below are some great resources on how to make your own cheap alternative for a flex sensor using components such as a potentiometer, or materials that you will definitely have lying around the house.

Alternative DIY flex sensor method #1: Potentiometers

Using potentiometers to make a flex sensor glove;

The end result of this is not going to look like a flex sensor, however, it will have the same functionality. Also, this method was used for a glove, but you can easily use the same components and materials for other projects. Check link below for an in-depth look at how to make an alternate flex senor using potentiometers.

https://www.instructables.com/DIY-Cheap-and-Accurate-Alternative-for-Flex-Sensor/

Alternative DIY flex sensor method #2: Random materials

You might never have considered ever using paper and  tin foil/aluminium to make an alternative for a flex sensor. But, these cheap and readily available materials are perfect for exactly that. The end product will have the same form of a flex sensor that you will be after as well. 

Using paper and tin foil/aluminium method #1:

Using paper and tin foil/aluminium method #2:

https://www.hackster.io/Shahirnasar/simple-homemade-flex-sensor-ff54f0

Using velostat plastic bags and masking tape:

Other alternatives for a flex sensor

If you only require the resistance to be varied, there are many sensors/transducers that are available that can be an alternative for a flex sensor which include;

• Light Dependent Resistors (LDRs)
• Force sensors
• Potentiometers
• Piezoelectric sensors 
• Thermistors

The post What is an alternative for a flex sensor? DIY flex sensor appeared first on Electronic Guidebook.

You might be familiar with how robots are depicted in movies, with their human-like form,and almost most often than not, these robots in movies are evil, taking over humankind.

But, that is not the case. 

Robots are essential in many industries making our lives much easier by performing tasks with more efficiency. 

There is a lot involved in the design and construction of robotics. One important element is the selection of Sensors. 

Sensors are devices that give robots the ability to make ‘sense’ of the real world (the same way our five senses help us).

Below are some of the most common sensors used in robotics;

• Light sensors
• Proximity sensors
• Sound sensors
• Temperature sensors
• Acceleration sensors
• Magnetic sensors
• Force sensors 

This article shall take a deeper look into these sensors, and why they are used in the field of robotics.

Deeper look at sensors and robotics

To understand why a particular sensor is used in robotics, it will help to first learn a bit about Sensors and Robotics individually. So, let’s take a closer look at them. 

What are sensors?

Embedded systems (such as a computer)  in the most simplest form consist of inputs, a processor and outputs.

Let’s consider a computer. It has inputs (mouse, keyboard), a processor (Central Processing Unit), and outputs (printer, speakers, monitor).

So what is a sensor? 

A sensor is a type of input device whose main function is to ‘sense’ physical changes in the environment (real world) and provide this information to the processor of the system (in the form of a varying voltage or resistance).

Us humans have our own sensors. 

Five of them!

We have the ability to make sense of the environment around us through Touch, Smell, Sight, Taste and Sound. 

Just like a computing system, we too also have a processor (our brain), and outputs (muscles, arms, legs).

Imagine yourself at a party and the DJ plays your favourite song.

You are able to sense the sound waves traversing the airwaves using one of those five senses (in this case sound through your ears).

This information is sent to your brain (processor) which realises this is your favourite song! It then informs your body(output) to move uncontrollably (or controllably depending on your dancing skills) to the beat of the song. 

Sensors in computing and electronic systems work in the same manner. They provide information from the world to the processor who can deal with that information as needed. 

For example, let’s take a look at a fan heater. 

This fan heater will have a temperature sensor which has the job to sense the ambient temperatures to ensure that the temperature you set is maintained. 

If temperatures start to rise, the sensor will sense this rise, and then relay this information to the processor which can then suspend heating until temperatures fall back to the levels you set. 

Why we use sensors

But, are sensors really that essential? 

The simple answer is yes! 

There are many benefits to using sensors in embedded systems. 

Let’s go back to the heater. If it did not have a sensor, the temperature would rise above the level you set making the room hotter than you would like. 

Sensors provide a means of feedback of real world data so that changes can be made by the processor if needed.

Other advantages include;

• Making systems more efficient
• Predictive and preventative maintenance
• Increasing accuracy 

What is robotics?

Whether you would have seen one first hand or not, robotics plays a big role in our everyday life. While you might not have one in your house (currently), they are used in many industries.

Robotics is a field of computer science and engineering that deals with the design and construction of robots.

And what exactly is a robot?

Robots are a type of machine that can be programmed to carry out simple, or a series of complex tasks autonomously. This means that once programmed for a specific task, they can operate without the need of human intervention (unless they break down of course). 

However, robots can also be controlled manually by humans via an external remote controlled device. 

Robots are given tasks to perform that would otherwise have been performed by humans. These tasks are given to robots because they can perform them with more efficiency and without getting tired or bored, especially repetitive tasks where humans could lose focus (and they do not complain) 

Sometimes a task might be too dangerous for a human to perform. For example, mixing of hazardous chemicals. In this instance a robot would be better suited for the job.

While robots perform human based tasks, they do not always take the form of humans as depicted in pop culture. 

Different components of a robot in robotics

Every task is not the same, so for that reason there are a wide variety of robots available for different tasks across many different disciplines.

One robot might have a specialized component that will help it perform a task that other robots might not be able to perform.

However, while there are many different types of robots, there is a standard construction and set of components that stay true for all of them. These components include;

• Control System
• Sensors (input)
• Actuators (output)
• Power Supply 
• Add-ons

Control system

The first and most important part of robotics is the Control System. 

Robots are a type of embedded system , and central to every embedded system is the control system (as we saw earlier) which consists of something known as a Central Processing Unit (CPU), which could be a Microprocessor or Microcontroller.

Think of the control system as a human brain which is responsible for processing information, making computations, controlling muscular movements, etc.

The control system is essentially the brain of the robot helping it process information, make computations, and control outputs in the same manner. 

Sensors

Next up are Sensors.

As you know now, sensors play a crucial role in embedded systems and robotics is no different. Sensors provide robots with real world data which then can be processed by the control system. 

We shall take a closer look at what sensors are used in robotics later. 

Actuators

To be considered a robot, a device has to involve some sort of movement within its frame or body. This movement will help it to carry out actions whether it be moving forward, lifting, grabbing, etc.

I know I keep referring to the human body, but it is analogous to a robot. We have muscles (actuators), to help us walk, lift, grab, push, etc. 

Actuators are made up of devices such as motors that receive signals from the control system to carry out a specific task. 

They can be made of many different materials and are operated using either compressed air (pneumatic actuators), or oil (hydraulic actuators). 

Power supply

Electricity is essential to all electrical and electronic devices, machines, and components. 

A power supply is a crucial component of every robot. Without it, the robot will be rendered useless. 

If a robot is confined to a specific space, it might receive its electrical power from a more permanent source like AC mains.

But, if the robot is out in the field where it has no access to AC mains, it will contain a more temporary power source such as batteries. 

However, these batteries will more often than not be rechargeable through means such as solar power, so that the batteries do not have to be constantly replaced. 

Add-ons

The last component of robotics are the add-ons.

These are external equipment that are added on to the robot to perform a specific task for a specific application and are often interchangeable. 

This might be a spray paint can for painting a car, or a drill, or a scalpel for surgical robots. 

Different sensors used in robotics

Alright, let’s take a look at the different sensors used in robotics. 

Note, as mentioned earlier, there are many different types of robots. The sensors that will be covered might not be used in all robots, but they are the most common, and most of the robots will utilise them. 

Also, it comes down to the needs of the application.

Sensor #1 used in robotics: Proximity sensor

The first commonly used sensors in robotics are Proximity sensors. 

Movement is a big area of robotics, whether it be an autonomous robot on mars, or a robotic arm moving to pick goods. 

These robots need a means to be able to avoid obstacles (for autonomous robots), or to know when an object is within reach to pick up (for robotic arms).

Proximity sensors enable robots to detect objects at a distance without the need of physical contact, acting as the eyes of the robot. 

They consist of two parts; transmitter and receiver. 

The transmitter first transmits a signal, this signal is reflected off an object and returns back to the receiver alerting the robot of an object nearby. Depending on the complexity of the proximity sensor, it can calculate the exact distance of the object.

The two most commonly used proximity sensors in robotics include;

• Infrared Sensor (IR) – uses an infrared beam which is transmitted by the transmitter (it cannot calculate exact distance)
• Ultrasonic Sensor – ultrasonic sound waves are emitted by the transmitter (this type of sensor can calculate the exact distance of an object within a specified range)

Sensor #2 used in robotics: Temperature sensors

Next up are Temperature Sensors.

This type of sensor has the ability to measure the temperature of the air (ambient), a solid, or a liquid.

Temperature sensors can have many uses in robotics and can be used internally in the robot, or for external purposes.

When used internally, temperature sensors are used to ensure the temperature of the robotic system is within the safe working limits.

Robots will employ a lot of electronics and motors that can get hot very fast. Temperature sensors are used to alert the control system when things get too heated. 

When used externally, temperature sensors in robotics are used to measure the ambient air temperature,  temperature of objects or of a liquid. 

For example, a robot might be used to travel to depths of the ocean where measuring and recording temperature information would be vital for scientists or researchers. 

Common temperature sensors used in robotics include;

• Thermocouples
• Resistance Temperature Detectors (RTDs)
• Thermistors 
• Semiconductor based IC sensors

Sensor #3 used in robotics:  Sound sensors

Sound sensors are typically microphones which are the ears of the robot allowing it to perceive sound. 

They sense sound from the surroundings and convert it into a voltage which is then sent to the control system for further processing. 

A great application of sound sensors is voice recognition. This would come in handy in scenarios where you might need to control a robot but your hands are tied up.

One great example of this is in the surgery room, where a robot can assist a surgeon with an operation. The surgeon might have both hands full, but could still communicate with the robot using his or her voice. 

Sound sensors can also be used in robotics as a means of vibration detection. 

Sensor # 4 used in robotics: Force sensors

I mentioned earlier that a robotic arm will need a proximity sensor to know how close an item or object is when trying to pick it up.

Another crucial ability that is needed by the arm is how much force it should apply to pick up a specific item.

It could be picking an egg in one instance, and a rock in another (i’m exaggerating, but you get the point). In this scenario the claw (part of the arm used to pick up items) will need to apply less force when picking the egg compared to picking up a rock.

Force (or pressure) sensor is a sensor with exact ability that is needed by a robotic arm (which is to calculate the amount or force it is subject to).

The resistance of a force sensor varies depending on the amount of force applied to it (which is why they are also referred to as Force Sensitive Resistors)

Sensor #5 used in robotics : Accelerometer

An Accelerometer is a type of sensor that measures the acceleration of a body that it is used within. The accelerometer measures the force caused by sudden motion (acceleration). 

It can measure two types of acceleration; static or dynamic.

Static acceleration is defined by a constant force that acts on a body such as gravity due to its predictive and unchanged value of 9.8m/s.

Dynamic acceleration is unknown and not uniform. It is best described as being a vibration or shock to the system. 

Accelerometers also have the added advantage of measuring the tilt or orientation of an object by measuring the static acceleration of gravity. 

Many robots would greatly benefit from using accelerometers. One common example is Unmanned Aerial Vehicles (UAVs). 

Knowing information such as acceleration, and orientation for these flying vehicles is vital. 

Sensor #6 used in robotics: Light sensors

Light sensors, as the name might suggest, have the ability to detect varying levels of light.

The most common type of light sensor is the Photoresistor. The resistance of the sensor varies with varying light levels. 

The more light the less resistance, and  lower light levels increase its resistance. 

Other common types of light sensor include;

• Photovoltaic cells
• Photo-diodes 
• Photo-transistors

While not the go to, they can be used as a cheaper option for object detection compared to other dedicated proximity sensors which we saw earlier. 

Sensor #7 used in robotics: Magnetic sensors

Last up of commonly used sensors in robotics are Magnetic Sensors. 

This type of sensor is used to detect the presence of magnetic fields, as well as ferromagnetic and conducting objects. 

Again, there are many variations of the magnetic sensor, each having a different construction or working principle. But, the overall aim of each of them is the same, which is to be able to detect magnetic fields. 

Common magnetic sensors include;

• Hall-effect sensor
• Reed sensors

A hall-effect sensor is a class of sensor that has the ability to detect the presence and magnitude of a magnetic field. 

Not traditionally a sensor, a reed sensor is a type of switch that opens (or closes) in the presence of a magnetic field. While they can detect the presence of a magnetic field, they cannot measure the magnitude. 

One widely used application of magnetic sensors in robotics is to measure the speed and direction of motors. 

Why are sensors used in robotics?

Sensors play an important role in embedded systems. It gives them the ability to perceive the real world and collect vital information.

Robotics is no different. As you just saw, the many sensors used, help the robots with unique tasks that it would not be able to accomplish if it did not utilise them.

An autonomous robot would drive straight into the first object it encounters without the help of proximity sensors which aid in navigation.

Sensors enable robots to make sense of the real world. They also allow them to perform tasks with more effectiveness and efficiency compared to us humans. 

Do all fields of robotics use sensors?  

There are many applications where robotics lend a helping hand, which can include;

• Security
• Space exploration 
• Medical
• Hobbyist 
• Entertainment 
• Marine / Underwater exploration
• Manufacturing

All robots are built with similar components, and the sensor is one of the most important components, so no matter what field robotics are employed in, all of them require sensors.

The post Common sensors used in robotics appeared first on Electronic Guidebook.

Appliances like toasters, microwaves, dryers, dishwashers, hot water kettles, sandwich presses, air fryers, just to name a few. 

Another very crucial appliance is the Washing Machine. 

Whether you have one at home, or use one at your local dry cleaners, this appliance is an amazing piece of engineering that makes our lives so much easier.

Without a washing machine you would have to physically wash your clothes by hand (which isn’t very fun!).

Sensors play a vital role in many different parts of a washing machine to help it achieve the task of washing clothes and fabrics. 

Below are some of the sensors used in a washing machine;

• Temperature
• Rotor position
• Dirt
• Water level
• Optical
• Vibration

This article shall take a closer look at the different parts of a washing machine, types of sensor used, and why these sensors are essential in the overall functionality of the washing machine.  

Deeper look at sensors and washing machines

Before we dive into what sensors are used in washing machines, it will help to learn a bit more about the sensor and washing machine individually.

This will help you later understand why certain sensors are used for certain parts of a washing machine. 

But, if you aren’t too concerned with learning about sensors or washing machines, you can always skip straight to the section ‘What sensors are used in a washing machine’ further down. 

What is a sensor

Embedded systems (such as a computer)  in the most simplest form consist of inputs, a processor and outputs.

Let’s consider a computer. It has inputs (mouse, keyboard), a processor (Central Processing Unit), and outputs (printer, speakers, monitor).

So what is a sensor? 

A sensor is a type of input device whose main function is to ‘sense’ physical changes in the environment (real world) and provide this information to the processor of the system. 

Us humans have our own sensors. 

Five of them!

We have the ability to make sense of the environment around us through Touch, Smell, Sight, Taste and Sound. 

Just like a computing system, we too also have a processor (our brain), and outputs (muscles, arms, legs).

So, imagine you are at a party and the DJ plays your favourite song.

You are able to sense the sound waves traversing the airwaves using one of those five senses (in this case sound through your ears).

This information is sent to your brain (processor) which realises this is your favourite song! It then informs your body(output) to move uncontrollably (or controllably depending on your dancing skills) to the beat of the song. 

Sensors in computing and electronic systems work in the same manner. They provide information from the world to the processor who can deal with that information as needed. 

For example, let’s take a look at a fan heater. 

This fan heater will have a temperature sensor which has the job to sense the ambient temperatures to ensure that the temperature you set is maintained. 

If temperatures start to rise, the sensor will sense this rise, and then relay this information to the processor. The processor can then suspend heating until temperatures fall back to the levels you set. 

Why we use sensors

But, are sensors really that essential? 

The simple answer is yes! 

There are many benefits to using sensors in embedded systems. 

Let’s go back to the heater. If it did not have a sensor, the temperature would rise above the level you set making the room hotter than you would like. 

Sensors provide a means of feedback of real world data so that changes can be made by the processor if needed.

Other advantages include;

• Making systems more efficient
• Predictive and preventative maintenance
• Increasing accuracy 

Closer look at the washing machine

Let’s take a look at the washing machine. 

Whether you have used one or not, you would have no doubt come across a washing machine before. 

The main purpose of a washing machine is to wash different types of fabrics and clothing. It was created to make our lives easier by eliminating the manual labour needed for washing clothes with your hands (i.e, rubbing clothes together and squeezing water out of them).

The only manual labour associated with washing your clothes with a washing machine is loading the clothes into it.

Different types of washing machine

There are primarily two types of washing machine, which can be classed by how clothes are loaded into them; Top loading and Front Loading.

Top loading washing machines

This type of washing machine has its opening for the clothes at the top where clothes are loaded from. 

A great advantage of this type of washing machine is that you do not have to be constantly bent over while loading and unloading clothes.

Front loading washing machines

This type of washing machine has its opening for the clothes in the front where clothes are loaded from. 

According to studies this type of washing machine consumes less power, while giving the best washing results.

Different parts of a washing machine

Rather than having one part that performs all of the functionalities, the washing machine consists of many different parts each having a specific task that helps the washing machine achieve its ability of washing clothes and fabrics.

Taking a closer look and understanding the different parts will be of help later as to why particular sensors are used in the washing machine. 

While there are front and top loading versions, the parts that I am going to cover will be found in most washing machines. 

Let’s take a look. 

Part #1 of a washing machine: Washing machine tub

The bulk of a washing machine is the Washing Machine Tub. It usually consists of two parts; an inner tub and an outer tub.

In top load washing machines, the inner tub is commonly referred to as a wash basket, and in front load variations it is known as a drum.

The outer tub remains in a fixed position and has the job of holding the inner tub as well as collecting wash water so it can be drained. 

The inner tub is where you put all your clothes or fabrics and rotates back and forth in order to clean them. It can be made with various materials that include plastic, porcelain and stainless.

Part #2 of a washing machine: Agitator/Impeller and Lifter/Fins

We just saw that the inner tub is where you put all your clothes in and rotates back and forth to clean them. However, just rotating isn’t going to help much to remove stubborn dirt and grime.

In top loading washing machines, an Agitator or Impeller sits in the middle of the inner tub and aids in the cleaning of clothes. 

In front loading versions they are known as Lifters or Fins which help the tumbling and mixing of clothes inside the inner tub. 

Part #3 of a washing machine: Motor

The rotation and movement of the inner tub doesn’t happen by magic. It harnesses the awesome powers of a motor to do so.

In front load models, the motor sits at the bottom, whereas in top load versions it will reside in the back.

The motor can either be a direct drive, or a belt drive. 

Direct drive motors are connected directly to the inner tub, whilst belt drive motors are connected to the inner tub via a belt. 

Part #4 of a washing machine: Water inlet valve

The washing machine needs water to rinse and clean the clothes. 

It gets this water by using what is known as a water inlet valve. It consists of two ports, one for hot water and one for cold. 

However, sometimes water inlet valves will only have one port for cold water. These types have an internal heater to heat the water to the right temperature. 

Part #5 of a washing machine: Drain pump

Washing machines go through different cycles to wash clothes which include a main wash, first rinse, and final spin.

As you can imagine, the water after the first main wash is going to be very dirty. Using this same water during the different cycles to clean your clothes isn’t very hygienic. 

This is where the drain pump comes in.

It has the job of removing water before, during and after different wash cycles. 

Part #6 of a washing machine: Washer drain hose

As we just saw, the drain pump removes water from the inner tub. But, it needs somewhere to go. 

A drain hose is connected to the drain pump and provides a means for the water to travel through. It usually exits the washing machine from the bottom or the back and ends up in a sink where the water can be drained.  

Part #7 of a washing machine: Console and display

The console is the main interface which you use to interact with the washing machine and select the different settings such as cycles, timing, temperatures, fabrics, etc. 

What sensors are used in a washing machine

Like most electrical and electronic devices, machines, etc, washing machines will have gone through the evolution process and had changes from their initial versions.

However, their overall functionalities stay very similar (as we saw with the different parts of a washing machine). 

When it comes to Sensors, one washing machine might have more compared to another, however, there are a set of sensors that are common in every washing machine. 

Below are commonly used sensors in a washing machine. 

Sensor #1 used in a washing machine: Temperature

The first sensor that you would find in a washing machine is a Temperature sensor.

There are many different types of temperature sensors, each using different forms of technology and working principles to measure the temperature of air, liquid or solid objects. 

Common types include;

• Thermistor
• Resistance temperature detectors (RTD’s)
• Thermocouples

So, why are temperature sensors used in washing machines?

A washing machine isn’t just used to wash one particular type of garment or fabric. Because of this, it offers a range of temperatures for different fabrics to ensure they do not get damaged when washed. Also, during the different periods of a wash cycle, a range of temperatures are used.

Temperature sensors are used to measure the temperature of the water, relay this information to the water inlet valve to help regulate the flow of hot or cold water to maintain the desired water temperature. 

As well as measuring the temperature of water, temperature sensors are used to measure the temperature of the motor to make sure it does not overheat (which has the potential of damaging it).

Sensor #2 used in a washing machine: Hall-effect / Reed sensor

Next up are Hall-effect sensors  and Reed sensors. 

A hall-effect sensor is a class of sensor that has the ability to detect the presence and magnitude of a magnetic field. 

Not traditionally a sensor, a reed sensor is a type of switch that opens (or closes) in the presence of a magnetic field. While they can detect the presence of a magnetic field, they cannot measure the magnitude. 

Both of these devices are very versatile and have many different uses in washing machines. Let’s take a look at some. 

Measuring motor speed

As we saw earlier, the inner tub is the part of the washing machine that rotates with the help of a motor.There are many different wash cycles each having their own speed of rotation of the inner tub. 

Hall-effect sensors are used in washing machines to detect the speed of the motor to ensure the inner tub is at the right speed for the right wash cycle. 

The hall effect sensor also has one added benefit of being able to detect the direction of rotation of the motor.

Lid/Door position

As a safety measure, washing machines do not begin any cycle if the lid/door is open, as water could spill out. 

It will only commence a wash cycle if it is closed.

Reed sensors are used to detect when the door is open or closed. They are contactless giving them a greater lifespan. 

Water level

Water is constantly being pumped in and out of a washing machine for the many different wash cycles that it goes through (as different wash cycles may require different amounts of water).

But, just randomly pumping water in or removing it is not an effective method, as you might add or remove too much causing incorrect levels of water.

A crucial component is knowing the current level of water so that the right amount of water can be pumped in or out. 

While there are many methods to measure water levels, one very common one is using a reed float sensor, which comprises two parts; a reed switch housed within a shaft, and a magnet inside a float. 

The float sits in the water and moves up and down with varying water levels. The reed switch within the housed unit closes whenever the float comes within close proximity.  

Dial position

You might just be washing a small load, or require low temperatures, or high soak levels, etc. A washing machine has many different features and functions for different fabric types.

The console is where a user interacts with the washing machine to select the right settings.

While earlier models had less features and used buttons, newer models have many more features and utilize a rotation dial.

Earlier, washing machines used mechanical selector switches for the rotation dial. However, mechanical switches wear out fast.

A better option for a rotation dial is a Rotary Hall-effect sensor which has no moving parts giving it a longer lifespan.

Vibration

Last up for hall-effect and reed sensors, is detecting vibrations in a washing machine. 

You might have witnessed it for yourself, and seen that washing machines can get quite violent and vibrate at alarming rates.

These vibrations can cause damage to the motor’s bearings and couplings. Some can vibrate enough to move them within a given area. 

Reed sensors are used to measure the magnitude and frequency of vibrations within a system, machine or equipment susceptible to frequent vibrations. 

They help ensure that vibrations do not exceed set limits. 

Sensor #3 used in a washing machine: Optical

Finally, the last type of sensor used in a washing machine is an Optical sensor.

These types of sensors detect light or a change in light levels. They can detect electromagnetic radiation from infrared to ultraviolet.

They are used in washing machines to determine the light permeability of water which can reveal things like how much dirt or detergent is present. 

Are weight sensors used in a washing machine?

You might have noticed that I haven’t included a sensor to measure the weight of the load. But, washing machines have a certain limit of weight they can handle.

So how does a washing machine know if you have exceeded the limit of weight if it does not have weight sensors?

Rather than using a sensor, the washing machine knows how much the load weighs depending on the resistance placed on the motor (how much work the motor has to do to rotate the inner tub). 

The lighter the load, the less resistance placed on the motor, and vice versa. 

If the weight exceeds the limit, the motor will not have sufficient power to rotate the inner tub. 

Would a washing machine function without sensors?

Sensors play an important role in many embedded systems, and the washing machine is no different. 

While there might be some aspects where a washing machine might function without a sensor (as we just saw with the weight of clothes), other instances, sensors are crucial and needed.

We saw the different parts of the washing machine where sensors were used earlier. Removing just one of them would cause issues. 

For example, if we removed the reed sensor which detects the water level, the drain pump would not know when to stop pumping water in, which could lead to overflows. 

So, a washing machine would not function properly without the help of sensors.

The post Sensors used in a washing machine appeared first on Electronic Guidebook.

How would you navigate the real world? 

Our five senses help us make ‘sense’ (pardon the pun) of the physical world around us. They help us see (sight) where we are going, hear (sound) music, feel (touch) raindrops, smell perfumes and taste foods. 

They do much more than those things of course, but you get the jist.

Sensors in the electronic world play pretty much the same role (and probably why they are called sensors for that reason).

They help computing and electronic systems by allowing them to get physical real world data.

One of those sensors helping these types of systems and used in many applications is the Ultrasonic Sensor.

But, what exactly are ultrasonic sensors?

Ultrasonic sensors are a type of proximity sensor which are used for detecting the distance of an object, or the presence of objects, without the need of physically making contact with those objects. The ultrasonic sensor uses ultrasonic sound waves (hence the name) to detect objects.

This is just the tip of the iceberg when it comes to the ultrasonic sensor. If you want to learn more about these awesome sensors, read on! 

Deeper look at sensors

Since an ultrasonic sensor is a subcategory of Proximity sensors, which is furthermore a subcategory of the broader term Sensor, it will help to learn a bit more about sensors, as well as proximity sensors. 

But, if you aren’t too concerned with learning about sensors or proximity sensors, you can skip straight to the section all about ultrasonic sensors. 

What is a sensor

Computing and electronic systems in the most simplest form consist of inputs, a processor and outputs.

Let’s consider a computer. It has inputs (mouse, keyboard), a processor (Central Processing Unit), and outputs (printer, speakers, monitor).

So what is a sensor? 

A sensor is a type of input device whose main function is to ‘sense’ physical changes in the environment (real world) and provide this information to the processor of the system. 

Us humans have our own sensors. 

Five of them!

We have the ability to make sense of the environment around us through Touch, Smell, Sight, Taste and Sound. 

Just like a computing system, we too also have a processor (our brain), and outputs (arms, legs).

So, imagine you are at a party and the DJ plays your favourite song.

You are able to sense the sound waves traversing the airwaves using one of those five senses (in this case sound through your ears).

This information is sent to your brain (processor) which realises this is your favourite song! It then informs your body(output) to move uncontrollably (or controllably depending on your dancing skills) to the beat of the song. 

Sensors in computing and electronic systems work in the same manner. They provide information from the world to the processor who can deal with that information as needed. 

For example, let’s take a look at a fan heater. 

This fan heater will have a temperature sensor which has the job to sense the ambient temperatures to ensure that the temperature you set is maintained. 

If temperatures start to rise, the sensor will sense this rise, and then relay this information to the processor. The processor can then suspend heating until temperatures fall back to the levels you set. 

Why we use sensors

But, are sensors really that essential? 

The simple answer is yes! 

There are many benefits to using sensors in systems. 

Let’s go back to the heater. If it did not have a sensor, the temperature would rise above the level you set making the room hotter than you would like. 

Sensors provide a means of feedback so that changes can be made if needed.

Other advantages include;

• Making systems more efficient
• Predictive and preventative maintenance
• Increasing accuracy 

What are proximity sensors?

Now that we know what role a sensor has in a computing or electronic system, we can take a closer look at Proximity Sensors.

Just like we have different sensors that have different roles, and function in different ways, the electronic world has many different types of sensors each with its own unique sensing ability. 

There are sensors to detect temperature, smoke, gas, altitude, speed, acceleration, and many more. 

What about a proximity sensor? What does it do? 

Proximity sensors are a classification of sensors that have the ability to detect objects without the need of physically touching them. 

However,you aren’t limited to only one type of proximity sensor to achieve this. There are a variety of technologies used such as light, sound, infrared, electromagnetic, and capacitance, in proximity sensors that give them the ability to detect objects.

However, the main type of proximity sensor that we are concerned with in this article are Ultrasonic Sensors. 

What are ultrasonic sensors?

So, how does an ultrasonic sensor detect objects without physical touch?

An ultrasonic sensor detects objects using ultrasonic sound waves (hence the name). 

Ultrasonic sound waves (or ultrasound) sit at a frequency (greater than 20kHz) much higher than the upper audible limits that the human ear is capable of hearing (which is around 20kHz).So, you won’t hear any annoying sounds when near ultrasonic sensors.

However, while you might not be able to hear it, the physical properties of ultrasound do not differ from normal sound that we hear.  

Construction of an ultrasonic sensor

A typical ultrasonic sensor is broken into two parts;

• Transmitter (generates the sound waves)
• Receiver (which captures the sound waves when it reflects back from an object)

Below is a picture of what a typical ultrasonic sensor looks like. 

To achieve the high sound frequencies, the ultrasonic sensor uses Piezoelectric Crystals. They oscillate at a high range of frequencies. 

A typical ultrasonic sensor comes with 4 pins;

• VCC (connects to the positive rail of the power supply. Usually +5V)
• TRIG (connects to a digital output pin of a microcontroller)
• ECHO (connects to a digital input pin of a microcontroller)
• GND (connects to ground rail of the power supply)

I shall explain more about the connections of the ultrasonic sensor with a microcontroller later on. 

Working principle of an ultrasonic sensor

Let’s take a look at how this sensor goes about using ultrasound to find an object.

Looking at an example will help make things a bit more clearer.. Below is a diagram of an ultrasonic sensor placed in front of a wall. 

1. The first step involves the ultrasonic sensor converting electrical energy to a sound wave. This sound wave is emitted from the ultrasonic transmitter.  

2. Next, the sound wave travels through the air until it encounters an object, person, animal, etc (in this example a wall) 

3. The sound wave then hits the object (wall) and reflects back toward the ultrasonic sensor

4. Finally the receiver of the ultrasonic sensor receives the reflected wave and a time stamp is calculated with the help of a microcontroller.(I shall explain in more detail how to calculate the distance using this time variable in the next section) 

How to calculate the distance of an object using an ultrasonic sensor?

Calculating the distance of an object using this sensor comes down to a fundamental equation which you would have learned about in high school science class, along with the fact that we know that the speed of sound, which is roughly 343 m/s (through dry air at around  20 °C).

Below is a fundamental equation to calculate speed, distance and time, which you might recall from science class;

Where V represents speed, d is distance and t is time.

Rearranging this equation to calculate distance we get;

We know that sound travels around 343 metres/second, so the next thing we need to calculate the distance of an object is time (which is obtained from the ultrasonic sensor). 

Note, the time value needs to be halved to calculate the distance of the object. This is because the time value the ultrasonic value will present to us, is the time it takes the sound wave to leave the transmitter, hit the object and return back to the transmitter.

We just need the time for the first part (which is the sound wave hitting the object) to calculate the distance of the object. 

To do this, we can either halve the time value when calculating the distance, or halve the total distance value at the end.

Let’s look at an example to clear things up. 

Say there is a wall about which you are trying to calculate how far away it is. The ultrasonic sensor gives you a time value of 0.005 seconds.

Option 1

Take this time value and divide it by 2. This now gives us a time value of 0.025 seconds.

Now, use this value and the speed of sound (343m/s), to calculate the distance. This gives us; Distance = 0.025 x 343 = 0.8575 meters.

Option 2

Use the initial value the ultrasonic proximity sensor gives us, calculate the distance and then divide it by 2. 

So, first calculate the distance; d = 0.005 x 343 = 1.715 meters. Now, take this value and halve it; 1.715 / 2 = 0.8575 meters.

So, using either option will yield the same result. 

Another important note is to make sure you are using the same units in your calculations. If you are calculating for meters per second, ensure your time values are in seconds and not milliseconds. 

What do I mean by this? 

Well, that time value we obtained from the ultrasonic sensor, can be either 0.005 seconds or 5 milliseconds. 

However, since the speed of sound is metres per second (m/s) and not meters per millisecond (m/ms), you will need to use time in the form of seconds which is 0.005. 

Can an ultrasonic sensor be used on its own?

No, unfortunately it cannot be used on its own. 

The ultrasonic sensor needs a microcontroller or microprocessor to unleash its full potential.

A microcontroller has two main functions when used with the senor;

• Trigger the sensor to transmit a wave
• Obtain the time of the reflected wave and calculate distance

Trigger the ultrasonic sensor to transmit a wave

The first function the microcontroller has is to trigger the ultrasonic sensor to transmit a sound wave. 

To do this, the TRIG pin on the sensor needs to be high (+5V) for a duration of around 10 microseconds (the ultrasonic sensor’s datasheet will also have the exact value it needs to be high for).

A microcontroller has many capabilities from analog to digital conversion, timing, serial communication, digital to analog conversion, and much more.

It also has a set of Digital Input and Output pins with each pin being bi-directional (this means you can assign a specific pin to be either an input or an output when programming the microcontroller). 

These digital pins allow you to control a wide variety of outputs (motors, LED’s, fans, etc), and gather information from many different types of inputs (buttons, switches, sensors, etc).

When set as an Output, the pin can be set to be either a Logic High (+5V), or a Logic Low (0V).

This is perfect for an ultrasonic sensor! You can connect the TRIG pin to one of the Digital I/O pins which has been set to an output. 

You then just have to program the microcontroller to make the TRIG pin a logic high, set a delay for 10 microseconds and then make the pin a logic low. 

The ultrasonic sensor will then transmit a sound wave. 

Calculate the time of the reflected wave

Earlier in the working principle section, I mentioned that the timestamp is calculated with the help of a microcontroller. This is because the ultrasonic sensor does not have the ability to calculate time on its own.

Lucky for us, the microcontroller also has the capability of timing using a set of Timers. 

Timers have many applications with the two main ones being; generating time delays, and measuring the time between two events.

‘Measuring the time between two events’ is perfect for use with the ultrasonic sensors. This means that we can measure the time between the Sound wave transmitted, and the Receiver receiving the reflected wave.

Another key pin of the sensor is the ECHO pin which gets connected to a digital pin of the microcontroller that is set as an input.  

When the receiver of the sensor detects the return of the reflected wave, the ECHO pin is set to a ‘logic low’ which is then read by the microcontroller. This helps us know when to stop the timer. 

Below are the sequence of steps of what happens inside a microcontroller’s code from triggering the ultrasonic sensor to calculating the time. 

1. Trigger ultrasonic sensor to transmit a sound wave via TRIG pin
2. Start the timer 
3. Reflected wave returns, and is detected by sensor’s receiver
4. ECHO pin goes low
5. Stop the timer
6. Acquire time value
7. Calculate distance

Ultrasonic sensor connection to a microcontroller

The connection of the ultrasonic sensor to a microcontroller is pretty basic as it only has four pins that need to be connected.

Another great thing is that the ultrasonic sensor and microcontroller both operate at the same voltage which is +5 volts. 

Below is the connection of an ultrasonic sensor and a microcontroller. 

A note to make is tha thet ECHO and TRIG pins can be connected to any of the digital pins of the microcontroller. 

However, since the digital pins can be either an input or output (depending on how you configure them when programming the microcontroller), you will have to make sure you configure the pins according to which of the ultrasonic sensor pins are connected to them (ECHO is an input and TRIG is an output). 

Standard specifications of an ultrasonic sensor

Ultrasonic sensors have a certain set of specifications that help you choose the right one for the application. 

While there are a wide variety of ultrasonic sensor brands available, they are not identical in their specifications. 

However, below is a list of average values an ultrasonic sensor might typically have;

• Operating voltage: 3.3V – 5V
• Operating current: 8mA
• Nominal Frequency : 40kHz
• Coverage distance: 0.2m (0.65ft) – 6m (19.7ft)
• Resolution: ~1cm (0.4 inches)
• Sound pressure: 112dB (min)
• Measuring angle: 15 degrees
• Input pulse: 10 microseconds 

What materials can an ultrasonic sensor detect?

I was recently using the ultrasonic sensor for a simple project which was to detect when someone entered the room. 

Initially I had set up the sensor at a height that was aiming at the torso (mid-section) of a person. However, when it came to testing, the ultrasonic sensor hardly detected me when I entered its sensing area(or it was not effective 100% of the time, which isn’t ideal).

Then I just moved the sensor to floor level (now aimed at my legs), and I started getting better results. 

What was the difference? 

I was wearing shorts! I had no fabric material covering my legs, whereas my t-shirt was absorbing the sound waves rather than reflecting them.

After doing some research, I confirmed my conclusions were right. Ultrasonic sensors are not good with soft or irregular objects, as they might either absorb the wave or redirect them elsewhere. 

I know, my project isn’t full proof due to the fact that someone might be wearing pants which will cause the same issues as before. 

The ideal objects for detection using an ultrasonic sensor are large, flat surfaces. Objects such as;

• Metals
• Ceramics
• Glass
• Wood

Common applications of ultrasonic sensors

The ultrasonic sensor has many different applications where it makes use of its unique capabilities for sensing without the need for physical contact. 

As you can imagine, there are a multitude of industries that could make use of this sensor. But, rather than naming all of them, I will list some of the more common applications where you might find an ultrasonic sensor. 

• Car parking sensors– lets you know if you are getting too close to a wall, another car, or any object (can be located in the front of the back of the car)
• Level control – detect, monitor and regulate levels of liquids within a closed container
• Anemometers – measuring wind speed and direction
• Robotics – help robots navigate their surroundings by detecting objects 
• Counting  – used in manufacturing factories to count goods on conveyor belts
• Medical – Produce images of internal organs, identify tumors and monitor health of babies inside the womb

Again, this isn’t an exhaustive list by any means. There are many more applications with similarities to those mentioned above, so rather than naming them all of them I will save you the time by not repeating myself. 

Can you use an ultrasonic sensor with an Arduino or Raspberry pi?

Yes, you can use an ultrasonic sensor with an Arduino or a Raspberry Pi.

As we saw earlier, the sensor requires a brain (either a microcontroller or microprocessor) to process the information it sends them.

Both the Arduino and Raspberry pi come as development boards that have a microcontroller or microprocessor which are capable of the functions required to operate the ultrasonic sensor.

These boards also have convenient pin slots for inputs, outputs, VCC and GND that you can connect the sensor’s pins to.

Why do we need ultrasonic sensors

But, why use ultrasonic sensors at all? 

While you could survive without having to rely on ultrasonic sensors, utilising their abilities far outweigh not using them.

The most obvious reason we need this type of sensor is to detect objects without the need of physical touch. Also, if you need to acquire the distance of the object (to within a 1cm) this sensor will be beneficial.

Below are some other examples of why you might need ultrasonic sensors.

In the simple case of parking a car, you might be the best parallel parker in the world, but sooner or later your senses are going to fail you, and mistakes will happen (in the form of bumping the car in front or behind).

However, if you enlist the abilities of an ultrasonic sensor, you now have an ‘extra pair of eyes’. While you still have to park the car, you can be assured that the sensor will be a more efficient guide. 

Another example is counting products on a conveyor belt. Sure, you could hire a human to do it. But, us humans have our limits of efficiency and effectiveness. Sooner or later, fatigue is going to set in and errors will be made. 

An ultrasonic sensor does not get tired, therefore you have higher efficiency. 

So, we need ultrasonic sensors as they make systems more efficient, effective, and accurate. 

Advantages and disadvantages of ultrasonic sensors

Everything in life comes with its good side as well as bad. 

The same is true for ultrasonic sensors too. Below is a list of the advantages and disadvantages of the sensor.

Advantages of ultrasonic sensors

• Detection without the need of physical contact
• Color and transparency of an object does not affect detecting abilities 
• Low current consumption
• Can give accurate distance of object (near to 1cm / 0.4in)
• Effective during the day as well night
• Can operate in ‘high-glare’ environments 

Disadvantages of ultrasonic sensors

• Acoustic noises near the operating frequency of sensor can cause interference in readings
• Cannot work in a vacuum 
• Unable to detect soft or irregular shaped objects well 
• Temperature fluctuations can affect the speed of the sensor’s ultrasonic sound waves 

Other alternatives to ultrasonic sensors

As you now know, the ultrasonic sensor is a type of proximity sensor which utilises sound to detect objects.

But, you are not limited to just using ultrasonic sensors for detection. There are many other types of proximity sensor available each using different methods and technologies to achieve detection on an object without the need of physical touch. 

Each will have its own set of unique characteristics as well as advantages which will make them suitable for particular applications.

Let’s take a quick look at each type of proximity sensor.

Inductive proximity sensor  – Uses the law of induction to detect metal based objects. This means other non-metal based objects cannot be detected using this type of sensor.

Capacitive proximity sensor – This type of proximity sensor is able to detect both metal and non-metal based objects. It does so by detecting the change in capacitance within the sensor when objects enter its sensing field.

Infrared (IR) proximity sensor – Has a very similar working principle to the ultrasonic sensor. But, rather than emitting a sound wave, this sensor emits a beam of infrared light. Also, just like sound waves emitted by the ultrasonic sensor cannot be heard, the light emitted by the IR sensor is invisible to the naked eye. 

Photoelectric proximity sensor – also emits a beam of light like the IR sensor, but is not limited to just infrared light.

Magnetic proximity sensor – This type of sensor employs technology which is capable of sensing magnetic based objects.

If you want a more in-depth guide about these types of proximity sensor, check this article.

The post What are ultrasonic sensors?An in-depth guide appeared first on Electronic Guidebook.

Whether it be in your smartphone, an aeroplane, street lights, your car and many other places.

Sensors are used in computing, as well as electrical and electronic systems. They are crucial in providing data from the real world to help the system make necessary changes.

They also help make these systems more efficient and accurate. 

There are many different types of sensors, each with a particular set of skills, making them suited for different applications. 

One of those types is the Proximity Sensor.

But, what are proximity sensors?

Proximity sensors help detect objects without the need of physical touch. They can detect the movement of an object, or the mere presence of it. Once they have detected an object, they can send this information to the brain (usually a microprocessor) of the system for further processing. 

This is only the tip of the iceberg for proximity sensors. There are many different types, each suited for a different type of application.

So read on to learn more about proximity sensors. 

Deeper look at sensors

Since the proximity sensor is a subcategory of the general term Sensor, it will help to learn a bit more about sensors.

But, if you aren’t too concerned with learning about sensors, you can skip this section and go to the next part which will cover everything about proximity sensors. 

What is a sensor

Computing and electronic systems in the most simplest form consist of inputs, a processor and outputs.

Let’s consider a computer. It has inputs (mouse, keyboard), a processor (Central Processing Unit), and outputs (printer, speakers, monitor).

So what is a sensor? 

A sensor is a type of input device whose main function is to ‘sense’ physical changes in the environment (real world) and provide this information to the processor of the system. 

Us humans have our own sensors. 

Five of them!

We have the ability to make sense of the environment around us through Touch, Smell, Sight, Taste and Sound. 

Just like a computing system, we too also have a processor (our brain), and outputs (arms, legs).

So, imagine you are at a party and the DJ plays your favourite song.

You are able to sense the sound waves traversing the airwaves using one of those five senses (in this case sound through your ears).

This information is sent to your brain (processor) which realises this is your jam! It then informs your body(output) to move uncontrollably (or controllably depending on your dancing skills) to the beat of the song. 

Sensors in computing and electronic systems work in the same manner. 

They provide information from the world to the processor who can deal with that information as needed. 

For example, let’s take a look at a fan heater. 

This fan heater will have a temperature sensor which has the job to sense the ambient temperatures to ensure that the temperature you set is maintained. 

If temperatures start to rise, the sensor will relay this information to the processor. The processor can then suspend heating until temperatures fall back to the levels you set. 

Why use sensors?

But, are sensors really that essential? 

The simple answer is yes! 

There are many benefits to using sensors in systems. 

Let’s go back to the heater. If it did not have a sensor, the temperature would rise above the level you set making the room hotter than you would like. 

Sensors provide a means of feedback so that changes can be made if needed.

Other advantages include;

• Making systems more efficient
• Predictive and preventative maintenance
• Increasing accuracy 

What are proximity sensors?

Now that we know what role a sensor has in a computing or electronic system, we can take a closer look at Proximity Sensors.

Just like we have different sensors that have different roles, and function in different ways, the electronic world has many different types of sensors each with its own unique sensing ability. 

There are sensors to detect temperature, smoke, gas, altitude, speed, acceleration, and many more. 

What about a proximity sensor? What does it do? 

Proximity sensors are a classification of sensors that have the ability to detect objects without the need of physically touching them. 

However,you aren’t limited to only one type of proximity sensor to achieve this. There are a variety of technologies used such as light, sound, infrared, electromagnetic, and capacitive, in proximity sensors that give them the ability to detect objects.

We shall cover the different types of proximity sensors in the next section. 

Different types of proximity sensors and their working principle

Now that we know the basic principle of a proximity sensor, let’s take a look at the different versions, and how each of them is able to detect objects with its own unique abilities. 

Inductive proximity sensors

First on the list are Inductive Proximity Sensors.

This type of proximity sensor is able to detect objects based on the law of Induction. Due to this, they are limited to only sensing Metal Objects.

Inductive proximity sensors are further divided into two categories;

• Unshielded 
• Shielded 

The main difference between the two is their Sensing area. 

This comes down to the electromagnetic field generated by the coil. In the Unshielded version of the sensor, the electromagnet field is not restricted, therefore it has a wide sensing area.

Whereas, in the Shielded version, the electromagnetic field is concentrated, reducing the sensing area more toward the front of the sensor. 

Working principle of Inductive proximity sensors

Below are the main stages of operation for inductive proximity sensors;

1. The coil generates a high-frequency electromagnetic field which originates from the coil located in the oscillation circuit
2. This field sensing area is dependent on whether it is Shielded or Unshielded.
3. Now, if a metal object enters this electromagnetic field, the metal object will be induced with a current known as an Eddy current due to electromagnetic induction.
4. If the metal object gets closer to the sensor, the eddy current is going to increase. 
5. This means that the oscillation circuit whose job it is for generating the electromagnetic field is going to have a greater load on it to keep up with the increase in eddy current.
6. A separate circuit inside the sensor is responsible for monitoring the load on the oscillation circuit and when it crosses a set threshold it will stop the oscillation circuit. 
7. This indicates the presence of an object. 

Capacitive proximity sensors

Next up, we have Capacitive proximity sensors. 

Objects are detected when their capacitance (and therefore a change in capacitance) is registered within the sensor. 

Unlike inductive proximity sensors, this version is not limited to detecting only metals. 

Metallic and non-metallic objects which range from liquids, metals, wood, plastic, etc, can be detected using capacitive proximity sensors. 

The internal construction is very similar to a Capacitor.

As you might know a capacitor consists of two conducting plates, which are separated by something known as a Dielectric. 

Similarly, the sensor consists of the two plates (electrodes) whose capacitance changes as an object moves toward it. 

Working principle of capacitive proximity sensors

The working principle is very similar to an inductive proximity sensor. 

As you just saw, the capacitive proximity sensor also has an oscillation and detection circuit. Below are the main stages of operation;

1. The internal plate (electrode) is connected to an oscillation circuit which generates an electrostatic field. 
2. When an object enters the electrostatic field, the capacitance of the plates increases
3. This increase causes a greater load on the oscillation circuit (just like with the inductive proximity sensor).
4. The detection circuit ‘detects’ this increase and stops oscillation, thereby indicating the presence of an object. 

Ultrasonic proximity sensors

The Ultrasonic proximity sensor detects objects by using sound.

Ultrasonic sound waves (hence the name), are used so they are not audible to humans (therefore you won’t hear anything if you are near these sensors).

A typical ultrasonic sensor is broken into two parts;

• Transmitter (generates the sound waves)
• Receiver (which captures the sound waves when it reflects back from an object)

The great thing about this type of proximity sensor is that you can measure the distance of the object. This comes down to knowing the speed of the sound, and the time it takes for the wave to make a return trip.

Below is a fundamental equation to calculate speed, distance and time, which you might recall from science class;

Where V represents speed, d is distance and t is time.

Rearranging this equation to calculate distance we get;

We know that sound travels around 343 metres/second. So, to calculate the distance of an object we just need to acquire the time.

Note, the time value needs to be halved to calculate the distance of the object. This is because the time value the ultrasonic value will present to us, is the time it takes the sound wave to leave the transmitter, hit the object and return back to the transmitter.

We just need the time for the first part (which is the sound wave hitting the object) to calculate the distance of the object. 

To do this, we can either halve the time value when calculating the distance, or halve the total distance value at the end.

Let’s look at an example to clear things up.

Say there is a wall about which you are trying to calculate how far away it is. The ultrasonic sensor gives you a time value of 0.005 seconds.

Option 1

Take the time value and divide it by 2. This now gives us a time value of 0.025 seconds. Now, use this value and the speed of sound (343 m/s), to calculate the distance. This gives us; Distance = 0.025 x 343 = 0.8575 meters.

Option 2

Use the initial value the ultrasonic proximity sensor gives us, calculate the distance and then divide it by 2. So, first calculate the distance; d = 0.005 x 343 = 1.715 meters. Now, take this value and halve it; 1.715 / 2 = 0.8575 meters.

So, using either option will yield the same result. 

Another important note is to make sure you are using the same units in your calculations. If you are calculating for meters per second, ensure your time values are in seconds and not milliseconds. 

Working principle of ultrasonic proximity sensors

Below are steps of operation for ultrasonic proximity sensors;

1. Transmitter emits an ultrasonic wave
2. Wave traverses through the air
3. The wave encounters an object hits it thus causing it to reflect back toward the ultrasonic sensor
4. Receiver ‘receives’ the reflected wave 

Infrared proximity sensors

While ultrasonic sensors use sound to detect objects, Infrared Proximity Sensors (or IR sensors) use infrared light. 

The infrared sensor works in many ways like its ultrasonic counterpart. Just like the sound waves are inaudible to the human ear, the infrared light is invisible to the naked eye as its wavelength is longer than visible light. 

If an object is able to give off heat, it will also give off infrared radiation. 

This type sensor comes in two varieties;

• Active
• Passive

Active Infrared Sensors have the capacity not only to detect IR radiation, but to produce their own IR radiation. 

An active IR sensor consists of two parts; a Infrared Light-Emitting-Diode (LED), and a Receiver. 

They are commonly used in robotics for obstacle detection. 

Passive Infrared Sensors on the other hand can only detect IR radiation and have no means of producing it. 

A passive IR sensor consists of the following parts;

• Two strips of a pyroelectric material
• An infrared filter (only lets in IR light)
• Fresnel lens (which takes in light an concentrates at a particular point)

Working principle of infrared proximity sensors

Active Infrared Proximity sensor

• The IR LED emits a beam of infrared light
• That beam hits an object and is reflected back toward the sensor
• The receiver then receives the reflected beam 
• The relative distance of the object is then calculated

Passive Infrared Proximity sensor

• The sensor will have a particular sensing field of view, as well as sensitivity to IR levels (which you should be able to change as you desire)
• When an object, person, animal, etc (that gives off IR radiation) enters the field of view, and has an IR reading above the threshold of the sensor’s IR level, a signal is then sent to the processor within the IR sensor indicating an object is present. 

Photoelectric proximity sensors

Next up are Photoelectric Proximity Sensors.

This type of sensor also uses light as its means of detecting objects. However, Infrared light is only used some of the time and is not necessarily the only type of light source used. 

The basic functionality of light being transmitted and reflected back to detect objects is the same. 

But, when it comes to photoelectric proximity sensors, there are three varieties;

• Reflective
• Through beam
• Diffuse 

Working principle of Photoelectric proximity sensors

Reflective Photoelectric proximity sensors

• A light beam is emitted from the transmitter
• That light beam bounces off a reflector and back to a detector
• If the light beam is able to reflect back with no interruption, this means there is not object present
• However, if the beam does not return to the transmitter, this indicates the presence of an object 

Through beam Photoelectric proximity sensors

• This setup of the sensor consists of two separate modules that are not part of the same housing; an Emitter and a Receiver
• The two modules are set up at some distance apart (but maintaining a direct line of sight between the emitter and receiver modules)
• The emitter emits a light beam to the receiver
• Under normal conditions, the light beam is unbroken
• If the beam is broken, it means there is a presence of an object or person

Diffuser Photoelectric proximity sensors

• Instead of the light reflecting of a reflector (like with the reflective photoelectric sensor), the object being detected acts as the reflector
• Emitter emits beam of light
• Light bounces of object and returns back to receiver 
• Presence of object detected

Magnetic proximity sensors

Last, but not least, is the Magnetic Proximity Sensor. 

This type of sensor is used to detect magnetic objects (things like permanent magnets and electromagnets). 

As you know, all magnetic objects are surrounded by a magnetic field. The sensor has technology which is able to detect this magnetic field. 

Here are different ways (or principles) that a magnetic proximity sensor might use to detect the presence of a magnetic field;

• Reed switch
• Variable reluctance 
• Magneto resistive 
• Hall-effect 

There are a couple of key characteristics of magnetic sensors; Rated operating distance and Repeatability.

Rated operating distance is the distance at which the magnetic sensor gets tripped (senses a magnetic field). 

Repeatability is the distance at which the sensor starts to repeatedly switch. 

Working principle of magnetic proximity sensors

Below are the working principles of the different types of proximity sensor.

Variable reluctance magnetic proximity sensor

• It is made up of a permanent magnet and a ferromagnetic pole surrounded by a coil of wire.
• When a magnetic material passes the tip of the ferromagnetic pole, an analog voltage is induced within the sensor 
• This voltage is sent to a control unit and converted to a digital signal for further processing

Magneto resistive proximity sensor

• Has something known as a Measuring Cell which consists of resistors with miniscule ferromagnetic and non-magnetic layers
• Two of the resistors form what is known as a Wheatstone bridge circuit. 
• When a magnetic field is present, the wheatstone bridge produces a larger signal proportional to the magnetic field. 
• A threshold value is defined and a comparator is used to switch the output signal. 

Reed switch magnetic proximity sensor

• Is a type of switch (hence the name), that is magnetically actuated.
• Made up of two ferromagnetic reeds (or contact blades), housed in a glass capsule
• In the presence of a magnetic field, the contacts close.

Hall-Effect magnetic proximity sensor

• Consist of a Semiconducting material (like Silicon).
• When placed in a magnetic field, the voltage changes depending on the strength of the magnetic field.

Which is best proximity sensors

Phew!

That was quite a list wasn’t it? If you weren’t aware that so many types of proximity sensors existed, now you do!

You might be on the hunt for a proximity sensor yourself, or you might just be curious as to know which is the best proximity sensor?

Well that question really comes down to the application and the needs of the application it will be used for. So, let’s take a look at the advantages and disadvantages of each type of proximity sensor. 

Inductive proximity sensors

Advantages

• Detection without the need for contact
• Resistant to most environmental factors such as dust and dirt
• Can sense a wide range of metals
• Cheap
• Longer lifespan due to no moving parts

Disadvantages

• Limited to a small distance it can sense objects 
• Can only detect objects that are metal
• Performance can be affected by certain temperatures 

Capacitive proximity sensors

Advantages

• Can detect a wide variety of materials (not limited to metals)
• Able to detect objects through non-metallic walls
• Has sensitivity control via a potentiometer (able to control for which materials you want to sense)
• Long lifespan due to no moving parts

Disadvantages

• Low sensing range
• Can be on the expensive side

Ultrasonic proximity sensors

Advantages

• Color and transparency of object does not affect detection
• Works well in extreme conditions
• Can be used in the dark
• Not affected by light sources 
• Low current consumption
• Able to give distance measurements to the nearest centimeter/inch

Disadvantages

• Cannot be used in a vacuum 
• Cannot detect soft surfaces such as fabrics, or surfaces with severe imperfections 

Infrared proximity sensors

Advantages

• Can be used anytime of the day
• Secured communication via line of sight 
• Can measure distance of soft objects

Disadvantages

• Other sources of infrared light (like the sun) can affect the sensor’s readings
• Performance deteriorates over longer distances 
• Passive infrared sensors can only detect objects that give off their own IR. 

Photoelectric proximity sensors

Advantages

• Can sense a wide range of materials
• Long lifespan
• Long sensing range 
• Fast response time 

Disadvantages

• Can get contaminated over time 
• Color of object can affect the sensing range 
• Installation of through beam versions of the sensor can be quite complex

Magnetic proximity sensors

Advantages

• Small packages 
• Large sensing range
• Long operating periods and low power consumption
• Low cost

Disadvantages

• Limited to only detecting magnetic materials
• Reed switch versions have lower lifespan due to moving parts

Common applications of proximity sensors

As mentioned at the start, sensors can be found everywhere. They are part of your daily lives helping make it more efficient and accurate. 

The proximity sensor is one of those sensors helping to enrich our lives. 

With the different types of proximity sensor available, and each having its own ability for specific purposes, it has many uses for many different applications. 

Below is a list of the general applications that the range of proximity sensors covered above can be used in;

• Object detection, positioning, inspection and counting in automated production lines in manufacturing companies
• Capacitive touch switches on consumer electronic products like smartphones, keypads etc 
• Collision detection for robots
• Washrooms; to turn taps/faucets, as well as hand dryers on and off without the need for contact
• Unmanned vehicles; Self driving cars, and planes 
• Passive infrared sensors used in security systems in businesses and homes 
• Detection of fluid levels, composition and pressure (using capacitive proximity sensors)
• Wind speed and direction on Anemometers (Ultrasonic)
• Parking sensors in automobiles 

The post What are proximity sensors? An in-depth guide appeared first on Electronic Guidebook.

But, what kind of things can set off a motion detector? The most commonly used motion detectors utilise Passive Infrared (PIR) technology to detect motion. This means that they can detect the motion of a moving object that emits infrared energy. This means that anything that emits high enough levels of infrared energy as well as a change in temperature can set off the motion detector which can include:

• Humans
• Animals 
• Heaters
• Sunlight

There are other types of motion detectors available which are used to detect motion. I will cover them and what sets them off in this article. The PIR type motion detector is just the most common.

How does a motion detector get set off?

Motion detectors come in a variety of designs which can get set off using different types of technology. You have a choice of different types of motion detectors available to perform the same job of detecting motion.

I will quickly discuss each type of sensor and how each gets set off and detects motion. 

Motion detector type #1 : Passive Infrared

The first of the motion detectors is the Passive Infrared (PIR) detector. This is the most common type of motion detector used in home security systems and automatic lighting systems. 

A PIR motion detector contains two slots which are made of material capable of detecting Infrared energy. 

A PIR motion detector that is not detecting any motion, it is said to be idle. In this state, both slots detect the same amounts of Infrared energy. 

When a body like a human or animal moves in front of the PIR detector, it will cross one half of the PIR sensor which causes a positive differential change between the two slots. 

This is what sets off the PIR motion detector.

A note should be made that a change in ambient temperature will not set off the motion detector as both slots will see the same change in temperature. Only when there is positive differential change between the two slots will the PIR motion detector be set off. 

This type of sensor does not emit any infrared beam and is why it is known as Passive Infrared.

What can set off a Passive Infrared motion detector?

Since the PIR motion detector is set off by a change in temperature, below is a list of bodies, objects that can potentially set if off:

• Humans
• Animals (Including insects)
• Heater
• Sunlight (if there is a change in light levels and temperature)
• Automobiles driving past
• Fire

Motion detector type #2 : Microwave

The Microwave motion detector is next on the list.

This type of motion detector uses electro-magnetic radiation to detect motion. 

An electro-magnetic wave is sent (through a transmitter), which then bounces off objects and is reflected back to the receiver. 

The receiver can use this information to see whether an object is moving within a given space or not. 

If an object is moving, the reflected wave is altered in its return time. 

If an object is stationary however, the reflected wave will return back to the receiver at the same rate. 

A great capability of a Microwave motion detector is that it can tell if an object is moving towards or away from it, not just past it. 

What can set off a Microwave motion detector?

A microwave motion detector will be set off purely by things in motion (not a change in temperature), as this is what alters the waves emitted by the detector. 

So things that can set off a microwave motion detector include:

• Humans in motion
• Animals motion
• Objects thrown in front of the motion detector
• Curtains moved by the wind
• Automobiles
• Basically anything in motion

Motion detector type #3 : Ultrasonic

Next we have the Ultrasonic motion detector. 

A Ultrasonic motion detector works in similar principle to the Microwave motion detector.

However, instead of emitting a microwave, it emits a sound wave of very high frequency (above the hearing capabilities of humans).

The Ultrasonic Motion Detector’s transmitter first sends a sound wave. When that wave encounters bodies,objects, etc, it gets reflected back to the detector’s receiver which will calculate the time it took. 

Much like the microwave, if the wave’s return time is altered, this is an indication of motion.

What can set off a Ultrasonic motion detector?

Since the ultrasonic motion detector detects motion in a similar fashion to the microwave motion detector, the things that can set it off are purely things that are in motion and modify the wave of the ultrasonic motion detector. 

These things include, movement of humans, animals, objects etc. 

Motion detector type #4 : Vibration

As the name suggests, vibration motion detectors detect motion purely through vibration. 

The simplest vibration motion detectors contain a sensor that has the ability to sense vibration. When a vibration occurs the vibration sensor is set off and lets the central processing unit know that motion has been detected. 

What can set off a Vibration motion detector?

For a vibration motion detector to be set off, it will require a person, animal, object, etc to generate a vibration that is within its vibration sensitivity limits. 

The disadvantage of this type of motion detector is that it requires a certain level of vibration to set it off. If a person is careful enough and tip toes their way around the motion detector it will not be set off. 

Motion detector type #5 : Tomographic

Tomographic motion detectors consist of multiple nodes (of receivers) set up in a space. Radio waves pass from node to node that create a mesh like network (like a laser system that you see in the movies).

When there is a disturbance anywhere in the network of nodes (ie someone walking past, an object being thrown past etc), the motion detector is set off. 

What can set off a Tomographic motion detector?

Things that can set off a tomographic motion detector include movement that breaks the path of the radio wave which can include humans, animals, objects (anything with considerable mass to break the path of the radio wave)

Motion detector type #6 : Video camera

Last on the list of the different types of motion detectors is a Video Camera Motion Detector. 

This type of motion detector utilises a video camera and software to detect movement. It does not use any special sensor to detect infrared energy or emit any special waves. 

When something moves in front of the video camera’s field of view, software then can detect changes in picture and thus motion is detected.

What can set off a Video camera motion detector?

To set off a video camera motion detector, the thing that is being detected needs to be big enough to be captured by the video camera and analysed by the software. 

Again, only motion will set off a video camera motion detector. 

Applications where a motion detector is used

We have established the different types of motion detector and how they can be set off which include infrared, sound, vibration and video camera. 

But, what are the applications where motion detectors can be used?

Due to their operating principle of detecting infrared and motion, they are primarily used in applications where motion needs to be detected.

The first most common area motion detectors are used are security systems. You might have a security system installed where you currently live. It will no doubt utilise motion detectors in different rooms to detect motion.

A security system is vital in homes, businesses, etc, as it provides a way to keep your household and everything you own safe when you are not at home. If a burglar enters your home/business the motion detectors will be set off and trigger an alarm and your security company. 

When set off, the motion detector can also be programmed to trigger a video camera to start capturing footage. 

Another common and useful application where motion detectors are used include automatic lighting. 

Imagine you are walking towards your house in the dark of night. Trying to walk with no illumination can be very hard. 

Automatic lighting using a motion detector can ease your pain by illuminating the path to your home. Also, leaving the light on throughout the night can make a dent in your electricity bill. A motion detector will only turn on the light when it is set off.

Other applications of motion detectors include:

• Automatic ticket gates
• Automated toilet flushes
• Hand dryers
• Automatic doors

Can small insects and animals set off a motion detector?

When it comes to small insects and animals, the Passive Infrared (PIR) motion detector is more susceptible to being set off.

This comes down to the fact that all living things emit varying amounts of Infrared energy. 

Obviously humans emit larger amounts of Infrared and therefore the chances of setting off a motion detector is higher. 

For small animals or insects, they need to be much closer to the sensor and be within the motion detectors Field of View (FoV) to set it off.

If the small animal or insect is at a considerable distance from the PIR motion detector, it will not be set off as they do not emit high levels of infrared to trigger it. 

How to prevent a motion detector being set off by small animals and insects

But, what if you want to eliminate or lower the chances of your motion detector being set off by small animals or insects completely. Is it possible?

There are ways that you can lower the chances of a motion detector being set off.

Dual Technology Motion Sensor

As the name suggests, this type of motion detector includes two types of motion detection; Infrared and Microwave/Ultrasound. 

This will drastically reduce the chances of small animals and insects setting off the motion detector as it needs to both detect infrared and motion in order to be set off.

Placement of the Motion Detector

Even with dual technology motion detectors, if mounted in places that are easy to get to, or lower to the ground, this will still be set off.

Mounting motion detectors higher off the ground and in corners will reduce the chances of it being set off by animals and insects.

Lower Sensitivity 

You might be wondering, what about creepy crawlies and insects that can fly and can get to any nook and cranny imaginable. Placement of a motion detector will not affect them.

Your best option here with PIR motion detectors is to reduce their sensitivity levels. However, this does not mean you are lowering the infrared level sensitivity. This means that the motion detector will require higher levels of infrared to be set off.

As small insects have lower levels of Infrared, lowering the sensitivity will reduce the chances of it being set off. 

The great news is that a human intruder will still be able to set off the motion detector! 

Can you change the sensitivity of the motion detector to not get set off so easily?

Yes. You can change the sensitivity levels of motion detectors so that it takes either higher levels of Infrared or movement in order to set them off. 

Can a motion detector be set off by daylight?

Motion detectors that use Microwaves or Ultrasound, will not be affected by daylight as they use sound reflected off living things and objects to be set off. 

The issue of a motion detector being set off unwantedly by light is with PIR type motion detectors. 

As you know, PIR motion detectors get set off when there is a change in Infrared levels. Sunlight is a great source of Infrared energy.

If the PIR motion detector is exposed to a constant source of sunlight there should be much of an issue. 

Problems arise when there is change in light level. Maybe the light is shining onto the motion detector through a tree. If a wind blows and causes leaves to disrupt the sunlight beam, this could set off the motion detector. 

So, when placing your motion detector outside, make sure to mount it in a place where light levels are constant and do not have sudden changes. 

Can a low battery set off a motion detector?

Another reason that a motion detector could be set off is because of low battery levels. This can cause false triggering. 

Make sure to routinely check the battery levels of your motion detector and change it if required. 

Also, invest in good quality batteries as cheaper batteries lose their charge much faster. 

Can rain set off a motion detector?

While rain won’t set off a PIR type motion detector, it can set off motion detectors that detect motion using reflected waves such as the Microwave and Ultrasound motion detectors. 

Falling rain will cause a disruption in the times of reflected waves thereby causing the motion detector to be set off. 

To combat these either use PIR motion detectors outside or adjust the sensitivity of motion detectors that use reflected waves. 

Can wind set off a motion detector?

While sound cannot be reflected off of wind and has no Infrared signature to affect a PIR motion detector, as we saw above, wind only plays a part when it alters an object’s paths to disrupt light levels. 

So, wind itself cannot set off a motion detector, but it can set it off with its ability to move objects past the motion detector.

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A light sensor helps detect changes in light. 

Having the ability to sense the change in light has many advantages and can be utilised a countless of different ways.

But where are light sensors used? Light sensors are used in many different industries and for a number of different applications. They can be found in consumer electronics like Mobile phones and Tablets, Streetlights, Automobiles, security systems just to name a few of their applications. 

What is the purpose of light sensors?

Thanks to advancements in technology we have a range of sensors available at our disposal. Depending on your needs there are sensors that can sense  temperature, speed, humidity, gas, angles etc.

The light sensor is one of the many sensors available.It is a device that has the ability to convert light (which are photons) into electrical energy (in the form of electrons). 

It’s main purpose is to detect changes in light level, and sees it used in many different applications where light intensity is a major component of the application.

I will cover the common applications where light sensors are used later in this article.

Different types of Light Sensors

With light sensors, you have three types available. They are the Photoresistor, Photodiode, and Phototransistor. 

Photoresistor

A photoresistor light sensor is the most commonly used light sensor. It is used by hobbyists and makers due to its low price and availability. It is also known as a Light Dependent Resistor (LDR). The photoresistor varies its resistance depending on the intensity of light it detects.

The higher the light intensity of light, the lower the resistance, and vice versa. 

Photodiode

While the resistance of a photodiode light sensor varies depending on light levels, a Photodiode produces a varying electric current depending on the intensity of light. 

Brighter light levels cause a greeted current flow and vice versa. 

Phototransistor

The final type of light sensor is the Phototransistor. The phototransistor has the same working principle as the Photodiode, but with the added benefit of an amplifier. 

Due to this amplifier, the phototransistor has better light sensitivity. The downside is that it doesn’t do too well in lower light applications. 

Can light sensors work by themselves?

No, light sensors only have the ability to detect changes in light and output this information in the form of a voltage or current. They cannot do any processing on the information they detect. 

Let’s take one of our five senses as an example. Our eyes let us sense the world around us visually. They have the ability to take in information. But, to make sense of that information we require a brain.

This is the same of light sensors. They require a brain, which can either be a Microcontroller or Microprocessor which are devices capable of taking the information that a light sensor outputs and processing it accordingly.

Applications of where light sensors are used?

You might not think that a light sensor has many uses, but it is a very versatile sensor that can be found in many applications. 

Below I have listed applications where light sensors are used. 

Application #1 where light sensors are used: Consumer Electronics 

The most common consumer electronic devices that use light sensors are Mobile Phones, and Tablets.

The light sensor is used in these devices to help with the auto-brightness function for the display. This is an essential function because the light sensor detects the light levels of the environment the user is using the device in and can adjust the brightness automatically. 

If the light sensor detects the environment to be dark, the brightness of the mobile phone and/or tablet does not have to be very high, so the brightness of the display can be reduced.

On the other hand, if the light sensor detects higher levels of light intensity, this will make it harder for the user to read the display and therefore the brightness of the device’s screen is increased. 

Application #2 where light sensors are used: Automobiles

You might have experienced driving in the night and noticed an oncoming car with their headlights off. Or, you might have been the driver who forgot to turn your headlights on.

Not turning your headlights on while driving at night can have devastating circumstances. You are essentially invisible to other drivers, and pedestrians.

Older models of cars did not have the ability to automatically turn on its own headlights if the driver forgot to do so. 

Newer cars are now capable of automatically turning on their headlights when ambient light levels drop (or you enter a tunnel) thanks to light sensors. 

Application #3 where light sensors are used: Streetlights

Headlights on cars help illuminate the road better, giving the driver better vision at night, and also giving other drivers and pedestrians better view of the car. 

But, there is only so much that a car headlight can illuminate the road. 

Another way of helping the drivers with night time driving is the use of Street Lights. They also help illuminate roads which help the driver see where they are going. 

Streetlights are also beneficial for people walking on footpaths. It lets people see where they are walking and helps them avoid any potential obstacles. Also, walking in the dark can be quite daunting. Having footpaths that are lit gives pedestrians a bit more reassurance.

Turning on streetlights manually every night is very inefficient. Also sun rises and sets at different times everyday.

Using light sensors allows them to turn on and off at the right time everyday. This also helps save electricity.

Application #4 where light sensors are used: Security

There are many forms of security systems to help keep you and your personal things safe. 

Lasers are often used in security because their beam is invisible to the naked eye. You can create a barrier of sorts when you use a laser in combination with a light sensor.

They are often used at the entry of stores and workplaces which lets owners know when someone has entered. 

Application #5 where light sensors are used: Horticulture

Plants and trees are essential to life. Without them we would not survive. They provide us with Oxygen that helps us breathe, as well as food to feed us. 

Growing plants, and trees is not a simple task. It requires a lot of care and thought like choosing the right soil to plant seeds, how much water to use and how much sunlight the plant receives. 

If a plant is left out in the burning sun without getting watered, the plant will get dehydrated and die. 

So how do light sensors help in the field of horticulture?

They are connected to sprinkler systems. The light sensor detects when the sun is at its brightest and activates the sprinkler system to ensure that plants and trees do not get dehydrated. 

They work in concert with other sensors to ensure that the right environment is created to allow plants and trees to thrive. 

Application #6 where light sensors are used: Safety

A fire can consume a house or workplace in a matter of minutes. No matter what time of the day, fires can be very dangerous.

But, they pose even more of a risk during the night when you are sleeping. A fire can start while you are asleep and you will not even be aware of it.

Smoke detectors were designed to alert you when a fire is present. There are many different types available, and one common type is the Photoelectric Smoke Detector. 

It uses light sensors to detect fires. The working principle is similar to that of the laser beam and light sensor mentioned above for the security system. An LED shines a beam of light inside the smoke detector toward the light sensor. When smoke disturbs the beam an alarm is sounded. 

Application #7 where light sensors are used: Medical 

Advancements of technology in the medical field have given us many life saving devices. 

Sensors play a big role in many of the medical instrumentation. 

Light sensors are used in devices such as the Pulse Oximetry (which helps measure the percentage of Hemoglobin) and Heart-Rate monitors (to measure heart rates). 

Application #8 where light sensors are used: Solar

Renewable energy is now becoming the new way of powering our world. It is more sustainable and better for the world. 

There are many different types of renewable energy and one abundant source is the Sun. 

Solar panels convert sunshine into electrical energy which then gets stored for later use. 

However, the sun does stay stationary in the sky. It moves across as the day goes by. In order to get the most energy from the sun, solar panels need to be positioned so they directly face the sun. 

But, they cannot do this on their own. Light sensors lend their helping hand by detecting where the sun rays are at their brightest and then position the solar panels accordingly to get the most out of the sun rays. 

Which type of light sensor are used in these applications?

I mentioned earlier the different types of light sensors, Photoresistor, Photodiode, and Phototransistor. I’ve covered some of the common applications where light sensors are used. 

Each type of light sensor has its advantages for different applications. 

Where are Photoresistor light sensors used?

Photoresistors are commonly used in applications where a slow response in light levels are sufficient such as turning on street lights, solar and horticulture applications.  

They are also great for lower light levels. 

Photoresistors are the go light sensor for hobbyists due to their ease of use, and low cost. 

Where are Photodiode and Phototransistor light sensors used?

When light levels change faster, and a quicker response is needed, Photodiode and Phototransistor light sensors are used. 

They are used for higher, more intense light levels.

Applications in the Medical Field, Smoke Detectors, Automobiles, Compact Disc Players etc use these kinds of light sensors. 

Where you wouldn’t use light sensors?

There are many different applications that require the help of some kind of sensor to detect a physical phenomenon like temperature, speed, gravity, etc.

Since there are so many sensors available, a light sensor wouldn’t be used for all of them. They would only be used where light is the main thing being measured. 

You wouldn’t use a light sensor to measure the temperature of a room. The need for a light sensor will present itself.

Final thoughts

Light sensors are a great and versatile tool that see them being used in many different applications across different industries such as Medical, Horticulture, Security, Safety and more. 

There are three types of light sensors used (Photo-resistor, Photo-diode, and Photo-transistor), each with their own advantages depending on the need of the application.

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