A Proximity Sensor detects an object’s presence when a target enters the sensor’s field of action. Proximity sensors detect the presence of the objects using electromagnetic fields, light, and sound. There are many types, each suitable for specific applications and environments.
The detection of a material or object in the vicinity leads to the initiation of individual action. The action to be triggered on detection is predefined. The detection of an object by means of a proximity sensor takes place without the physical contact of the sensor with the object. The proximity sensor uses some methods to operate.
Depending on the type of proximity sensor, the sensor can use sound, light, infrared or electromagnetic fields to detect a target.
Proximity sensor circuits that use eddy currents generated in metal objects of detection by electromagnetic induction systems that detect changes in electrical capacitance when approaching the object of detection.
Proximity sensors used in phones, recycling plants, self-driving cars, anti-aircraft systems, and assembly lines. There are many types of proximity sensors, and each detects targets differently.
The “proximity sensor” includes all sensors that perform non-contact detection compared to sensors such as limit switches that detect objects by physical contact. Proximity sensors convert information about the movement or presence of an object into electrical signals.
Proximity Sensor Applications
The proximity sensor has so many important uses. The main application of the proximity sensor is the detection of any object without physical contact. Because they generally perform very well in a wide variety of applications, proximity sensors are well suited for many industries such as food and beverage, chemical processing, oil and gas, pharmaceuticals, discrete manufacturing, and construction.
Their functionality, flexibility, and reliability enable proximity sensors to meet the requirements of most applications. Different types of proximity sensors can solve a variety of sensing tasks. Using the right sensor for the correct application minimizes downtime, reduces maintenance requirements, and increases the production efficiency.
Understanding the different principles of operation, performance, and applicability of each proximity sensor allows manufacturers to integrate the appropriate sensors into the desired applications
1. Counting of Pieces: One of the essential applications is the detection and measurement of any changes in the environment.
2. Rotation: Proximity sensors used in mobile phones for which we get screen rotation capabilities, car racing capabilities, a touch screen, automatic light off during phone calls, etc.
3. Speed Measurements: A proximity sensor used to measure the speed and distance of vehicles.
4. Liquid Level Detection: Proximity sensor used to detect liquid level.
5. Determine the Direction of Movement: Proximity sensor used in a home automation system, for example, to automatically turn on the light when anyone is present in the room.
6. The Direction and Rotation: proximity sensor used to measure the speed and direction of electric motors’ rotation.
7.Object Detection: The primary use of the proximity sensor is to detect any object without physical contact.
Uses of Proximity Sensor
Proximity sensors commonly used in industrial applications for food production to processing. The proximity sensor used in mobile phones. Different engineering projects use different proximity sensors for different functions. It,s also used in parking lots, breakage detection systems, and conveyor systems.
Proximity sensors are also used for detecting the proximity of other vehicles to their cars and for parking assist functions. There are many types of proximity sensors, and they use different detection methods. For example, capacitive and photoelectric sensors are more suitable for plastic and organic objects, while inductive proximity sensors can only detect metal objects.
Proximity sensors are available in different categories depending on their detection. Some proximity sensors are useful for material detection, and others used to detect different environmental conditions based on the following classification of proximity sensors.
Types of the Proximity Sensor
1 Inductive Proximity Sensor
2 Capacitive Proximity Sensor
3 Ultrasonic Proximity Sensor
4 Magnetic Proximity Sensor
5 Optical Proximity Sensor
Inductive Proximity Sensor
An inductive sensor is an electronic proximity sensor that detects metal objects without touching them. Inductive proximity sensors are useful for detecting metal objects near their active side. This sensor works on the electrical principle of inductance, where the fluctuating current induces an electromotive force (EMF) in the target.
Inductive proximity sensors are non-contact sensors used only to detect metal objects. It,s based on induction law, which drives a coil with an oscillator when a metal object approaches it. Inductive proximity sensors allow non-contact detection of metal objects at a distance of 5 mm to 60 mm.
The electromagnetic field generated by the coil is unlimited, making it possible to increase the sensing distance. The generated electromagnetic field concentrated in the front where the sides of the sensor coil are closed.
working of Inductive Proximity Sensor
Inductive proximity sensors detect magnetic losses due to eddy currents generated on a conductive surface by an external magnetic field. An AC magnetic field is generated at the detection coil, and changes in impedance due to eddy currents generated on the metal object are detected.
Inductive sensors currents induced by magnetic fields to detect nearby metal objects. An inductive sensor uses a coil (inductor) to create a high-frequency magnetic field. If there is a metal object near the changing magnetic field, the current will flow in it.
This net current flow creates a new magnetic field that opposes the original magnetic field. The net effect is that it changes the inductance of the inductive sensor coil. They work by creating a high-frequency field.
If the target approaches, the field induces eddy currents. These currents consume power due to resistance, so the field energy is lost, and the signal amplitude decreases. The detector examines the magnitude of the field to determine when it has been reduced enough to trigger.
2 Capacitive Proximity Sensor
One common type of sensor is a capacitive proximity sensor. As the name suggests, capacitive proximity sensors work by operating a change in the sensor’s capacitance read. A typical capacitor consists of two conductive elements (sometimes called plates) separated from some kind of insulating material, which can be one of many different types, including ceramic, plastic: Paper, or other materials.
While Capacitive Proximity sensors are non-contact devices that can detect the presence or absence of almost anything, regardless of the material. They use the electrical property of change in capacity and capacity based on changes in the electric field around the sensor’s active surface.
A primary Capacitive proximity sensor is used to detect the presence of objects or substances. What sets them apart from other sensors is that they do not come into physical contact with the perceived object, and for this reason, they are also called proximity sensors. Capacitive proximity sensors are used for non-contact detection of metal and non-metallic objects (liquids, plastics, wood materials, etc.).
Ability Capacitive proximity sensors use changes in the space between the sensor and the trace object. When an object is at a predetermined distance from the sensor’s sensitive side, the electronic circuit inside the sensor begins to vibrate. The rise or fall of these fluctuations is applied by a threshold circuit that drives the amplifier to operate from external loads.
Working of Capacitive Proximity Sensor
A capacitive sensor acts like a simple capacitor. The metal plate on the sensor’s sensing surface is electrically connected to the internal generator circuit, and the target to be detected acts as a second capacitor plate. It,s use the face or surface of the sensor as one capacitor plate and the surface of a conductive or dielectric target as the other.
The capacitance changes in inverse proportion to the distance between the capacitor plates in this device and a specific value can be set to trigger target detection. Unlike an inductive sensor, which generates an electromagnetic field, a capacitive sensor creates an electrostatic field.
The principle of operation of a capacitive proximity sensor is that one of the conductive elements or plates is located inside the sensor itself. The other is an object that needs to be detected. The inner plate is connected to the generator circuit, which generates an electric field.
The air gap between the inner plate and the outer object serves as an insulator or dielectric material. When an object is present, it changes the capacity value and is recorded as the object’s presence.
Ultrasonic Proximity Sensor
An ultrasonic sensor is an electronic device that measures the distance to a target by emitting ultrasonic sound waves and converting the reflected sound into an electrical signal. Ultrasonic waves travel faster than the speed of audible sound (that is, a person’s sound). Ultrasonic sensors are made up of two main components: a transmitter (which emits sound using piezoelectric crystals) and a receiver (which detects sound after it has reached and from a target).
Ultrasonic sensors work by emitting and receiving high-frequency sound waves. The frequency is usually about 200 kHz, which is too high for the human ear. An ultrasonic sensor is a piezoelectric transducer capable of converting an electrical signal into mechanical vibrations and mechanical vibrations into an electrical signal.
Hence, in a mono-static approach, the ultrasonic transducer is a transceiver that acts as a speaker and as a microphone at the same frequency. Ultrasonic Sensors Used to avoid and detect obstacles with robots such as a bipedal robot, obstacle avoidance robot, pathfinding robot,. It is also used to measure distance in a wide range from 2 cm to 400 cm.
Ultrasonic sensors can detect a variety of materials regardless of shape, or color. The only requirement for ultrasonic sensing is a solid or liquid target material. This enables non-contact detection of, Metal, Plastic, Sand, Oil, Wood, Water, Glass, Stones, and Non-sound absorbing materials.
Types of Ultrasound sensors
1 Determination of proximity
An object that exceeds the specified distance will be found and generate an output signal. The trigger point does not depend on the size, material, or reflection of the symbol.
2 Dimension range
The exact distance to the conductor and the moving object is measured between the time between the transmitted and reflected pulses of the ultrasound sound. The distance change is considered and displayed regularly.
Working of Ultrasonic Proximity Sensor
An ultrasonic sound sensor is a tool that measures the distance of an object using ultrasound sound waves. An ultrasound sensor uses a transducer to send and receive ultrasound pulses that report object proximity. Frequency high-frequency sound waves emerge from the boundaries and create clear sounds.
Ultrasonic proximity sensors emit and receive sound waves. The carrier signal is an inaudible high-frequency sound wave. They detect the presence of a target in one of two configurations. An ultrasonic sensor (or transducer) works on the same principles as radar. An ultrasonic sensor converts electrical energy into acoustic waves and vice versa.
An acoustic wave signal is an ultrasonic wave propagating at a frequency above 18 kHz. In diffuse or reflective sensors, the transmitter and receiver are housed in one housing. When the target enters the range of the device, the ultrasonic waves are reflected in the sensor.
Ultrasonic sensors work by sending a sound wave at a frequency higher than the range of human hearing.
The transducer acts as a microphone to receive and transmit ultrasonic sound. Like many others, our ultrasonic transducers use a single transducer to send a pulse and receive an echo. The sensor determines the distance to the target by measuring the time between sending and receiving an ultrasonic pulse.
Magnetic Proximity Sensor
Magnetic proximity sensors are non-contact proximity sensors that are used to detect magnetic objects such as permanent magnets. Combined with a separate “damping” magnet, the magnetic sensors provide extensive sensing ranges from a small housing size. It can detect magnets through walls of non-ferrous metal, stainless steel, aluminum, plastic, or wood.
Depending on the magnetic field’s orientation, the sensor can be damped from the front or the side. They sense the presence of a magnetic object, commonly referred to as a target. With its magnetic field, the target triggers the switching process when it enters the sensor’s detection range. The switch can be a reed switch, or the device can work due to the principles of inductive, variable resistance, magneto resistivity, or Hall effect.
Working of Magnetic Proximity Sensor
There are several operating or working principles of magnetic proximity sensors, including reed switches, inductive GMR sensors, variable resistance sensors, magneto-resistive sensors, or Hall effect sensors. Magnetic proximity sensors are triggered when a permanent magnet is present.
The principle of their operation is based on reed switches, the thin plates of which are hermetically sealed in a glass flask with an inert gas. The presence of a magnetic field causes the small plates to bend and touch each other, causing electrical contact. The plate’s surface is treated with a unique material that is especially suitable for low current or high inductive circuits.
Magnetic sensors use GMR or Giant Magneto-Resistivity Effect technology. The measuring cell consists of resistors with several very thin ferromagnetic and non-magnetic layers. Two of these GMR resistors are used to form a conventional Wheatstone bridge circuit that, when present in a magnetic field, produces a strong signal proportional to the magnetic field. The threshold is determined, and the output is switched via a computer.
Optical Proximity Sensor
An optical proximity sensor includes a light source and a sensor that detects light. These sensors detect objects directly in front of them by detecting the sensor’s transmitted light reflected from the object’s surface. A light source supplied because it is usually critical that the light is “adapted” to the light sensor system.
While the light source generates light at a frequency that the light sensor can best detect and is unlikely to be produced by nearby sources—infrared light used in most optical sensors. To make the photosensitive system more reliable, most optical proximity sensor light sources turn infrared light on and off at a fixed frequency. The light sensor circuitry designed so that light does not pulsate at this frequency deflected.
Working of Optical Proximity Sensor
An optical sensor converts the light beams into an electrical signal. The light sensor in an optical proximity sensor is usually a semiconductor device such as a photodiode that generates a small current when light energy hits it, or more often a phototransistor or photodarlington that allows current to flow if light strikes it.
Early light sensors used photoconductive materials, which became the best conductors and thus allowed current to pass when light energy hit them. A sensor control circuit is also required. The control circuit may need to match the transmitter pulse frequency with the light sensor.
The control circuit is also often used to switch the output circuit at a certain light level. Light beam sensors are also available that output a voltage or current proportional to the received light level.