How the sensor works. Hall sensor - the principle of operation from a school physics course. Homemade from a module for Arduino

- these are sensors that work without physical and mechanical contact. They work through an electric and magnetic field, and optical sensors are also widely used. In this article, we will analyze all three types of sensors: optical, capacitive and inductive, and at the end we will do an experiment with an inductive sensor. By the way, the people also call contactless sensors proximity switches, so don't be afraid if you see such a name ;-).

optical sensor

So, a few words about optical sensors ... The principle of operation optical sensors shown in the figure below

barrier

Do you remember any shots from films where the main characters had to go through optical beams and not hit any of them? If the beam was touched by any part of the body, an alarm was triggered.

The beam is emitted by some source. And there is also a “beam receiver”, that is, the thing that receives the beam. As soon as there is no beam on the beam receiver, the contact will immediately turn on or off in it, which will directly control the alarm or something else at your discretion. Basically, a beam source and a receiver, properly called a "photodetector", come in pairs.

SKB IS optical motion sensors are very popular in Russia.

These types of sensors have both a light source and a photodetector. They are located right in the body of these sensors. Each type of sensor is a complete design and is used in a number of machines where increased processing accuracy is needed, up to 1 micrometer. Basically, these are machines with a system H logical P software At board ( CNC) that work according to the program and require minimal human intervention. These non-contact sensors are built on this principle

These types of sensors are denoted by the letter “T” and are called barrier. As soon as the optical beam was interrupted, the sensor worked.

Pros:

range can reach up to 150 meters
high reliability and noise immunity

Minuses:

for long sensing distances, fine adjustment of the photodetector to the optical beam is required.

Reflex

The reflective type of sensors is indicated by the letter R. In these types of sensors, the emitter and receiver are located in the same housing.

The principle of operation can be seen in the figure below.

Light from the emitter is reflected from some reflector (reflector) and enters the receiver. As soon as the beam is interrupted by any object, the sensor is triggered. This sensor is very convenient on conveyor lines when counting products.

diffusion

AND last type optical sensors - diffusion - denoted by the letter D. They may look different:

The principle of operation is the same as that of the reflex, but here the light is already reflected from objects. Such sensors are designed for a small sensing distance and are unpretentious in their work.

Capacitive and inductive sensors

Optics are optics, but the most unpretentious in their work and very reliable are considered inductive and capacitive sensors. This is how they look like

They are very similar to each other. The principle of their operation is associated with a change in the magnetic and electric field. Inductive sensors are triggered when any metal is brought to them. They do not “peck” on other materials. Capacitive ones work on almost any substance.

How an inductive sensor works

As they say, it's better to see once than hear a hundred times, so let's do a little experiment with inductive sensor.

So, we have an inductive sensor as a guest Russian production

We read what is written on it

WBI sensor brand blah blah blah blah, S - sensing distance, here it is 2 mm, U1 - version for a temperate climate, IP - 67 - protection level(in short, the level of protection here is very steep), U b - voltage at which the sensor operates, here the voltage can be in the range from 10 to 30 volts, I load - load current, this sensor can deliver up to 200 milliamps of current to the load, I think this is decent.

On the reverse of the tag is a wiring diagram for this sensor.

Well, let's evaluate the work of the sensor? To do this, we cling to the load. The load we will have is an LED connected in series with a resistor with a nominal value of 1 kOhm. Why do we need a resistor? The LED at the moment of inclusion begins to frantically eat current and burns out. To prevent this, a resistor is placed in series with the LED.

On the brown wire of the sensor we supply a plus from the Power supply, and on the blue wire - a minus. The voltage I took was 15 volts.

The moment of truth is coming ... We bring to working area sensor metal object, and the sensor immediately works for us, as the LED built into the sensor tells us, as well as our experimental LED.

The sensor does not respond to materials other than metals. A jar of rosin means nothing to him :-).

Instead of an LED, a logic circuit input can be used, that is, the sensor, when triggered, outputs a logic one signal that can be used in digital devices.

Conclusion

In the world of electronics, these three types of sensors are in increasing use. Every year the production of these sensors is growing and growing. They are absolutely used different areas industry. Automation and robotics would not be possible without these sensors. In this article, I have analyzed only the simplest sensors that give us only an “on-off” signal or, to put it in a professional language, one bit of information. More sophisticated types of sensors can provide different parameters and can even connect directly to computers and other devices.

Buy inductive sensor

In our radio store, inductive sensors cost 5 times more than if they were ordered from China from Aliexpress.

Here You can look at a variety of inductive sensors.

Modern apartment plumber, builder and electrician Kashkarov Andrey Petrovich

How is the motion sensor

In the middle of the sensor are IR light receivers - photocells.

Fresnel lens consists of many small lenses, each of which focuses the IR light on the plane of the photocell, and one of them - directly on the photocell itself (the signal is recorded).

When a person moves, after some time the focus of the lens leaves the photocell and the signal disappears.

Then another lens focuses the infrared radiation from the person onto the photocell and the signal appears again.

Such an appearance-disappearance-appearance of a signal is a sign of the presence of a person.

Each lens covers its segment. The signal disappears when a person (human hand) goes beyond the boundaries of this segment.

When moving within a segment, the signal does not change. Several logical conclusions can be drawn from the foregoing.

1. The more such lenses, the smaller movements the sensor can capture.

2. With distance from the sensor, the size of the segment increases and from a certain distance all small movements, for example, the movement of hands, shaking the head, will be within the boundaries of one segment; after this distance, the presence detector can only work as a motion detector.

3. Motion sensors have larger segments than presence sensors.

4. Motion sensors respond to brighter IR light compared to presence sensors.

From the book Woman driving author Khannikov Alexander Alexandrovich

traffic safety

From the book Cunning Ways to Save Fuel. The main secret of the car author Gromakovsky Alexey Alekseevich

Driving speed One of the key factors affecting the efficiency of a car is driving speed. Everyone knows that the most economical driving mode is driving on a country road in calm weather at a speed of about 80-90 km / h at the highest (in

From the book Electronic Tricks for Curious Children author Kashkarov Andrey Petrovich

From the book The ABC of Tourism author Bardin Kirill Vasilievich

From Paula in Your House author Galich Andrey Yurievich

From the book Belly Dance. Master's Lessons. Advanced level author Vedekhina Tatyana Yurievna

From the book Former Citizen in the Village. Helpful Hints And turnkey solutions author Kashkarov Andrey

Temperature controller and sensor Heating control in cable systems carried out by means of automatic controllers, which provide precise and optimal temperature control in terms of both comfort and energy savings.

From the book Modern Apartment Plumber, Builder and Electrician author Kashkarov Andrey Petrovich

Chest movements Check your posture. Stand up straight, pull in your stomach, push your chest slightly forward, both feet are stable and firmly on the floor, arms are spread apart. We start chest movements. Without moving bottom body, with a short movement we raise (push out) the chest

From the book Ploskorez Fokin! Dig up, weed, loosen and mow in 20 minutes author Gerasimova Natalia

Hip movements Starting position: standing on a full foot, legs slightly apart (about the width of the foot) and located on the same line parallel to each other, the body is slightly tilted back, the back is straight, the stomach is relaxed, the arms are lowered along the body, the knees

From the author's book

Movements with an inclination Let's move on to the movements in the draw. Starting position: standing straight on a full foot (legs are on the same line), the body is slightly tilted back, the back is straight, the legs are shoulder-width apart, the knees are “soft”, the arms are at the sides. Pull the hips to the right and shift the weight

From the author's book

Movements with a shawl The dance with a shawl (scarf, veil, handkerchief) is one of the most traditional. A scarf can amazingly transform, decorate the movements of a dancer. Its possibilities are almost limitless, and therefore working with it is a special pleasure. Competently

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In our progressive time, science is moving at a fast pace, so it is not always possible to keep up with them. Some old dogmas are crumbling, some new ones are being put forward. Mankind does not stand still and should not stand still, but the engine of mankind is scientists, scientists. And at any moment a discovery can occur that can not only amaze the minds of the entire population the globe but also fundamentally change our lives.

A special role in science is allocated to medicine, since a person, unfortunately, is not immortal, fragile and very vulnerable to all kinds of diseases. Many people know that in the Middle Ages people lived on average 30 years, and now 60-80 years. That is, at least doubled life expectancy. This was influenced, of course, by a combination of factors, but it was medicine that played a big role. And, for sure, 60-80 years for a person is not the limit of average life. It is possible that someday people will cross the mark of 100 years. Scientists from all over the world are fighting for it.

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Inductive proximity sensor. Appearance

IN industrial electronics inductive, and other sensors are used very widely.

The article will be a review (if you want, popular science). Real instructions for sensors and links to examples are given.

Types of sensors

So what is a sensor anyway? A sensor is a device that emits a specific signal when a specific event occurs. In other words, the sensor is activated under a certain condition, and an analog (proportional to the input action) or discrete (binary, digital, i.e. two possible levels) signal appears at its output.

More precisely, we can look at Wikipedia: Sensor (sensor, from English sensor) - a concept in control systems, a primary converter, an element of a measuring, signaling, regulating or controlling device of a system that converts a controlled value into a signal that is convenient for use.

There is also a lot of other information, but I have my own, engineering-electronic-applied, vision of the issue.

There are a lot of sensors. I will list only those types of sensors that an electrician and an electronics engineer have to deal with.

Inductive. It is activated by the presence of metal in the trigger zone. Other names are proximity sensor, position sensor, inductive, presence sensor, inductive switch, proximity sensor or switch. The meaning is the same and should not be confused. In English they write “proximity sensor”. In fact, this is a metal sensor.

Optical. Other names are photosensor, photoelectric sensor, optical switch. These are also used in everyday life, they are called “light sensor”

Capacitive. Triggered by the presence of almost any object or substance in the field of activity.

Pressure. There is no air or oil pressure - a signal to the controller or breaks. This is if discrete. There may be a sensor with a current output, the current of which is proportional to the absolute pressure or differential.

Limit switches(electric sensor). This is a conventional passive switch that works when an object runs into or presses on it.

Sensors may also be called sensors or initiators.

Enough for now, let's move on to the topic of the article.

The inductive sensor is discrete. A signal appears at its output when metal is present in a given zone.

The proximity sensor is based on a generator with an inductor. Hence the name. When metal appears in the electromagnetic field of the coil, this field changes dramatically, which affects the operation of the circuit.

Field inductive sensor. metal plate changes resonant frequency oscillatory circuit

Diagram of an inductive npn sensor. A functional diagram is given, on which: an oscillator with an oscillatory circuit, a threshold device (comparator), an NPN output transistor, protective zener diodes and diodes

Most of the pictures in the article are not mine, at the end it will be possible to download the sources.

Application of inductive sensor

Inductive proximity sensors are widely used in industrial automation to determine the position of one or another part of the mechanism. The signal from the output of the sensor can be fed to the input of the controller, frequency converter, relay, starter, and so on. The only condition– compliance with current and voltage.

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Job inductive sensor. The flag moves to the right, and when it reaches the sensor sensitivity zone, the sensor is triggered.

By the way, sensor manufacturers warn that it is not recommended to connect an incandescent bulb directly to the sensor output. I already wrote about the reasons -.

Characteristics of inductive sensors

How are the sensors different?

Almost everything that is said below applies not only to inductive, but also to optical and capacitive sensors.

Construction, body type

There are two main options here - cylindrical and rectangular. Other cases are used extremely rarely. Housing material - metal (various alloys) or plastic.

Cylindrical probe diameter

Basic dimensions - 12 and 18 mm. Other diameters (4, 8, 22, 30 mm) are rarely used.

To fix the 18 mm sensor, you need 2 keys for 22 or 24 mm.

Switching distance (working clearance)

This is the distance to metal plate, which guarantees reliable operation of the sensor. For miniature sensors, this distance is from 0 to 2 mm, for sensors with a diameter of 12 and 18 mm - up to 4 and 8 mm, for large sensors - up to 20 ... 30 mm.

Number of wires to connect

Let's get to the schematics.

2-wire. The sensor is connected directly to the load circuit (for example, a starter coil). Just like we turn on the lights at home. Convenient for installation, but capricious to the load. They work poorly with both high and low load resistance.

2-wire sensor. Switching scheme

The load can be connected to any wire, for constant voltage it is important to observe the polarity. For sensors designed to work with AC voltage– neither load connection nor polarity matters. You don't have to think about how to connect them at all. The main thing is to provide current.

3-wire. The most common. There are two wires for power and one for load. I will tell you more separately.

4- and 5-wire. This is possible if two outputs to the load are used (for example, PNP and NPN (transistor), or switching (relay). The fifth wire is the selection of the operating mode or output status.

Types of sensor outputs by polarity

All discrete sensors can have only 3 types of outputs depending on the key (output) element:

Relay. Everything is clear here. The relay switches the required voltage or one of the power wires. This provides complete galvanic isolation from the sensor power circuit, which is the main advantage of such a circuit. That is, regardless of the sensor supply voltage, you can turn on / off the load with any voltage. Mainly used in large sensors.

Transistor PNP. This is a PNP sensor. The output is a PNP transistor, that is, the “positive” wire is switched. To the “minus” the load is connected permanently.

Transistor NPN.At the output - an NPN transistor, that is, the “negative” is switched, or neutral wire. The "plus" load is connected permanently.

You can clearly understand the difference by understanding the principle of operation and the switching circuits of transistors. This rule will help: Where the emitter is connected, that wire is switched. The other wire is connected to the load permanently.

Below will be given sensor wiring diagrams, which will clearly show these differences.

Types of sensors by output status (NC and NO)

Whatever the sensor, one of its main parameters is the electrical state of the output at the moment when the sensor is not activated (it is not affected in any way).

The output at this moment can be turned on (power is supplied to the load) or turned off. Accordingly, they say - normally closed (normally closed, NC) contact or normally open (NO) contact. In foreign equipment, respectively - NC and NO.

That is, the main thing you need to know about the transistor outputs of the sensors is that there can be 4 varieties of them, depending on the polarity of the output transistor and on the initial state of the output:

PNP NO
PNP NC
NPN NO
NPN NC

Positive and negative operation logic

This concept refers rather to actuators that are connected to sensors (controllers, relays).

NEGATIVE or POSITIVE logic refers to the voltage level that activates the input.

NEGATIVE logic: the controller input is activated (logic “1”) when connected to GND. S/S terminal of the controller ( common wire for digital inputs) must be connected to +24 VDC. Negative logic is used for NPN sensors.

POSITIVE logic: the input is activated when connected to +24 VDC. The S/S terminal of the controller must be connected to GND. Use positive logic for PNP sensors. positive logic is used most often.

There are options for various devices and connecting sensors to them, ask in the comments, we'll think together.

Continuation of the article -. In the second part, real schemes are given and practical use various types sensors with transistor output.

The modern automobile consists of many mechanical, electromechanical and electronic components. Optimum performance engine must be provided regardless of external conditions. When it changes external factors, the operation of nodes and components must adapt to them. Vehicle sensors serve as a kind of tracking device for the operation of the car. Consider the main sensors:

3. Air flow sensor in a car - what does it affect?

The principle of operation of the air flow sensor is based on measuring the amount of heat given off to the air flow in the engine intake manifold. Heating
the sensor element is installed in front of the vehicle's air filter. Change
air flow rate and, accordingly, its mass fraction, is reflected in the degree
changes in the temperature of the heating coil of the MAF sensor.

"Tripling" of the engine during operation and loss of power indicates a possible failure of the air flow sensor.

4. Oxygen sensor, lambda probe - sensor malfunction

An oxygen sensor or lambda probe detects the amount of oxygen left in the exhaust manifold after fuel combustion. The lambda probe is part of the electronic engine management system, which regulates the amount of fuel, ensuring its complete combustion. Increased fuel consumption characterizes possible malfunction sensor.

5. Throttle sensor - symptoms of malfunction

This sensor is an electromechanical device consisting of a sensing element and a stepper motor.

The sensitive element is
temperature sensor, and the stepper motor is the actuator.
This electromechanical device changes the position of the throttle valve
relative to the coolant temperature. Thus, the rotation frequency
crankshaft of the engine depends on the degree of heating of the coolant.

A characteristic symptom of a malfunction of this sensor is the lack of warm-up speed and increased fuel consumption.

6. Oil pressure sensor - functions, failure

On cars of the Japanese brand, a diaphragm oil pressure sensor is installed
type. The sensor consists of two cavities separated by a flexible membrane. Oil
acts on the membrane on one side, bending from pressure. In the measuring
The membrane of the sensor cavity is connected to the rheostat rod.

Depending on the pressure engine oil, the membrane flexes more or less, thus changing the overall resistance of the sensor. The oil pressure sensor is located on the engine block.

A burning oil pressure light on the car panel may indicate a sensor failure.

7. Is the knock sensor in the engine not working?

The engine knock sensor measures the ignition timing. At normal operation engine sensor is in "idle" mode. When the process changes
combustion in the direction of the explosive nature of the combustion of fuel-detonation, the sensor sends a signal electronic system engine control to change the advance angle
ignition in the direction of decreasing.

It is located in the area air filter on the cylinder block. To check the performance of the knock sensor, you must run.

8. Camshaft angle sensor - troit engine

This sensor is located on the cylinder head and measures the engine speed.
camshaft of the engine, and based on the signals from the sensor, the control unit determines the current position of the pistons in the cylinders.

Uneven engine operation and tripling indicate incorrect operation of the sensor. The check is carried out using an ohmmeter, measuring the resistance between the sensor terminals.

9. ABS / ABS sensor in the car - check the performance

ABS sensors electromagnetic type are installed on the wheels of the car and are included in the anti-lock braking system of the car.

Sensor function is the measurement of wheel speed. The object of measurement of the sensor is the signal gear disk, which is mounted on the wheel hub. If the ABS sensor is faulty, the control light on the control panel does not go out after starting the engine.

The technology for determining the operability of the sensor is to measure the resistance between the contacts of the sensor; in case of a malfunction, the resistance is zero.

10. Fuel level sensor in a car - how to check if it works?

The fuel level sensor is installed in the fuel pump housing and consists of several components. The float, through a long rod, acts on a sector rheostat, which changes the resistance of the sensor depending on the fuel level in the car's tank. The sensor signals are sent to a pointer or electronic pointer on the vehicle control panel. Checking the performance of the fuel level sensor is carried out with an ohmmeter, which measures the resistance between the sensor contacts.