Magnetic Hall sensors are widespread in modern conditions and are used not only in specialized products, but also in ordinary household appliances. Most users do not even suspect what sensitive elements work in their phone, for example, and what they can be installed not only in electronic equipment, but also in vehicles (in a car or motorcycle). In this article, we will look at the structure, principle of operation and purpose of the Hall sensor.
Content:
- Principle of operation and types
- Historical reference
- Classification
- Device and examples of use
- Application in ignition systems and washing machines
- In a domestic environment
Principle of operation and types
The use of sensors in various devices (in a tablet, in particular) is explained by their ability to react to field changes and turn off when the magnetic cover of the case is closed. Thanks to this property, they are also installed in washing machines, allowing you to control the drum rotation speed. In simple terms, here the Hall sensor is used as a tachometer.
Historical reference
To understand how this element works, a little history is required. In 1879, the American physicist Hall discovered an interesting phenomenon associated with the behavior of a conductor with a current in a magnetic field. The test showed that if a current is passed through a copper plate placed between the magnets, then a potential difference appears on its lateral faces. A natural question arises: how to check this voltage at home?
It turned out that in practice it can be measure with a multimeter or any other device within the appropriate limits. The same can be done with any suitable tester or similar device.
Connecting the meter confirms that the moving electrons under the influence of the magnetic field are deflected to the side (perpendicular to the direction of their movement).
Important! The magnitude of this deviation or potential difference is proportional to the "power" of the magnets and the strength of the current through the plate.
On this basis, Hall concluded that such a conductor is a good means of measuring the magnetic field. The operation of a special sensitive element called a Hall sensor is based on this effect. Having figured out how it works in each specific device, you can be sure of the final assimilation of its principle of operation.
Classification
It is important to understand what Hall sensors are, and by what principle they are usually classified. According to the peculiarities of work and what it is needed for or by purpose, the Hall sensor can have various designs. One of the varieties is analog devices that produce a continuous signal at the output.
In contrast to them, a digital element has only two discrete states ("zero" and "one"). This type of device can be unipolar or bipolar. The first of them is triggered when a field of any polarity is detected and turns off when it disappears. That is, the unipolar digital sensor reacts only to the absence or presence of magnetic tension. The considered features of each of the subspecies also help to understand what it is - a Hall sensor.
Unipolar sensors switch to "unity" only when the field reaches a threshold level and are not able to determine its presence at weak voltages. This property is a significant disadvantage of such devices, which significantly limits the scope of their application. The bipolar sensor is triggered taking into account the polarity of the magnetic field, one of which turns it on and the other turns it off.
The conventional graphic designation of devices of this class is shown in the photo below:
Device and examples of use
The simplest system with a Hall sensor includes the following elements:
- Permanent magnet (its function is to create a magnetic field).
- Movable rotor with blades or teeth.
- A special rod made of magnetic material (magnetic core).
- Plastic case.
In addition, the technical characteristics of the sensor provide for the use of microcircuits involved in the measurement process.
It is possible to understand the principle of operation of this device if you familiarize yourself with the detailed diagram of switching on the Hall sensor in the measurement area. The connection diagram and the essence of the sensor operation can be presented as follows:
- In the gap formed by the halves of the magnetic circuit, the metal rotor blades move.
- When they rotate, the magnetic flux is periodically shunted.
- The built-in microcircuit provides for the determination of a zero induction index (at these moments, the voltage at its output is maximum).
- The frequency of such bursts, calculated by the same microcircuit, is used to judge the rotation speed of the controlled object (the motor shaft in a motorcycle, for example).
In order for this process to proceed normally, when the sensor is connected to the measuring circuit, the pinout of this sample must be taken into account (it can be different).
Summarizing the considered scheme, it should be assumed that sensors of this class are capable of measuring the crankshaft rotation speed of any moving vehicle. The versatility of the sensor, which does not exclude the possibility of its installation in a scooter, for example, makes it possible to use the Hall sensor not only in complex technical devices, but also in ordinary household appliances.
Application in ignition systems and washing machines
When using a Hall sensor in the ignition system of a car, it can be used to record the moment of opening the distributor. In this case, it works as an analog converter, which determines the instant of interruption of the on-board power supply. Its use in the working modules of the washing machine is based on the same principle, which makes it possible to determine the increase in the weight of the laundry by the drum rotation speed.
Hall sensors are installed in some samples of measuring equipment. Most often, they are equipped with non-contact clamps used to measure current in conductors. The built-in device reacts to changes in the electromagnetic field generated around the power cable. In addition, it fits the throttle handle of an e-bike, allowing you to control its angle of rotation.
In a domestic environment
In computer keyboards, these devices provide a contactless way of reading information. The sensor, which is part of the cooler of a household PC, is able to control the polarity of the rotor windings, that is, to change the direction of its rotation.
When using such an element in a smartphone, in particular, it ensures that the device is turned off when it is placed in a case with a "magnetic" fastener.
Considering the field of application of Hall sensors in simple words, we can say that its use in the technical field is practically unlimited. In the electronic designer Arduino, for example, there is a set with such a sensor, which makes it possible to illustrate the Hall effect in practice.
This is not the only educational use case that helps novice users understand how to connect and use field sensors.
In conclusion, we note that the disadvantages of Hall sensors include their sensitivity to electromagnetic interference, which often occurs in working circuits. In addition, the use of complex electronic modules in the design of the device to some extent affects its reliability, somewhat reducing it. These disadvantages of the sensor are not considered as its defects, but are simply taken into account when working with the equipment.
Now you know what a Hall sensor is, how it works and why you need it. We hope the information provided was useful and interesting!
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