Use Of Hall Effect Sensor

The vast array of electrical engineering has a lot of things and can say terms to know and understand. One such term is the Hall effect sensor. Yes, here we will get to know about this term.

What do you understand by the Hall effect sensor?

A Hall effect sensor is an electronic device that adjusts its output voltage in response to variations in magnetic field density. It is named after American scientist Edwin Hall, who discovered that electricity and magnetism may work together to move objects. Hall sensors are used in applications such as proximity switching, positioning, speed detection, and current sensing. 

How Does a Hall Effect Sensor Work?

The sensor functions as an analog transducer in its most basic form, returning a voltage directly. It is possible to calculate the distance between the Hall plate and a known magnetic field. The precise location of the magnet can be calculated using groups of sensors. These sensors are used in a variety of applications, including automotive systems to sense position, distance, and speed. These ingenious components are employed in a variety of applications, but most notably in anti-lock braking systems (ABS) and internal combustion engines to help with ignition timing.

hall effect sensor

A Hall sensor is widely paired with circuitry that allows the device to operate in a digital (on/off) mode, and in this configuration, the device is referred to as a switch. They are commonly found in industrial applications, such as the pneumatic cylinder pictured, but they are also used in consumer electronics; for example, some computer printers use them to detect missing paper and open covers. They’re employed in keyboards when high dependability is necessary. Hall sensors are often used to time the speed of wheels and shafts, such as for digital readouts or timing the ignition of internal combustion engines. 

Hall effect sensor and magnets

Hall effect sensors, which are activated by the presence of an external magnetic field, include magnets. The device can then detect when an object moves closer or further away simply by measuring the strength of the magnetic field.

If a Hall effect sensor is installed in a door frame and a magnet is attached to the door, the sensor may identify whether the door is open or closed via detecting the magnetic field. A Hall effect sensor senses a magnet in the following way:

There are two key properties that all magnetic fields share. First, there’s what’s known as a ‘flux density,’ which refers to the volume of magnetic flow that passes through a unit area, and second, all magnets have two polarities (the North and South poles).

A Hall effect sensor’s output signal represents the density of a magnetic field surrounding the instrument. Hall effect sensors feature a pre-set criteria, and when the magnetic flux density exceeds that threshold, the device detects the magnetic field by creating a ‘Hall Voltage’ output.

Hall effect sensors all contain a thin piece of semiconductor material inside them that generates a magnetic field by passing a continuous electrical current through it.

This force causes electrons to migrate, resulting in a measured Hall voltage and the Hall effect sensor being activated.

The output Hall voltage from the Hall effect sensor is equivalent to the strength of the magnetic field that passes through the semiconductor material. Many Hall effect devices have built-in DC amplifiers, as well as logic-switching circuits and voltage regulators, to aid improve the device’s sensitivity (and hence effectiveness).

Different Types of Hall Effect Sensor

Hall effect sensors come in two varieties: One with linear (or analog) outputs and the other one with digital outputs. With an analog sensor, the output voltage rises in a strong magnetic field and falls in a weak magnetic field.

When using linear output Hall effect sensors, the output signal increases in parallel with the strength of the external magnetic field when the device comes into contact with the magnet until it approaches the power supply’s limits.

In contrast, the digital output device features a ‘Schmitt trigger,’ which is a bistable circuit that continuously increases and decreases the output as the voltage rises and falls to different thresholds. When the magnetic flux travelling through the Hall effect sensor exceeds the device’s preset value, the device’s output switches it from ‘off’ to ‘on’ thanks to the Schmitt trigger. The built-in hysteresis of the gadget eliminates any oscillation of the output signal when the sensor moves in and out of the magnetic field.

Types of Digital Hall effect sensors

There are two types of digital Hall effect sensors: bipolar and unipolar, which differ in terms of the magnetic field required to operate them.

Bipolar digital Hall effect sensors require a positive magnetic field (from the South pole of a magnet) to operate and a negative magnetic field (from the North pole) to release. Unipolar sensors require only a single magnetic South pole to operate and release as they move in and out of the magnetic field.

Because the majority of digital Hall effect sensors have limited output drive capabilities, they cannot directly switch large electrical loads. To counteract this, many digital sensors employ an open-collector NPN transistor. When the magnetic flux density exceeds the Hall effect sensor’s ‘on’ point, the transistor acts as a switch, shorting out the output terminal to the ground. There is a wide variety of Hall-effect switches available for a variety of different tasks.

Uses of Hall Effect Sensor

After explaining how Hall effect sensors work and the various types available, when do these devices prove to be very helpful? There are numerous Hall effect sensor applications, with the device’s applications varying depending on how the magnet is positioned and how it moves towards the sensor.

Magnet movement types include, among others, head-on, sideways, push-pull, and push-push, with these variations affecting how the sensor detects the magnetic field. The varying magnetic movements of hall effect sensors allow them to be used in a variety of applications. These devices are most commonly used to measure the presence, position, and proximity of objects in both industrial and domestic settings.

At home, you may have a Hall effect sensor in your printer that detects open covers or when the paper needs to be restocked. Because of the sideways detection movement, Hall effect sensors can be used as rotating speed sensors, which are especially useful for speedometers in cars and other vehicles, as well as bicycle wheels, gear teeth, and electronic ignition systems.

Current sensors, pressure sensors, and fluid flow sensors are also common applications for Hall effect sensors in industrial and manufacturing processes. 

Hall-effect sensors can also be used to measure DC magnetic flux in current transformers in an efficient and contactless manner.

Other Hall-effect sensor applications that require a contactless switch include electric air guns, go-kart speed controls, and the triggers of electro-pneumatic paintball guns.

Uses In automotive applications

One of the primary uses of Hall effect sensors is in the automotive industry, where the device is used in a variety of applications, including automotive fuel level indicators.

Hall effect sensors are used to measure fuel levels in two ways. To begin, a permanent magnet is attached to the surface of a floating object in a vertical float system, while the sensor is attached to the top of the tank, in line with the magnet. When you fill up your car or vehicle, the floating magnet rises to the top of the tank, bringing the magnetic field closer to the sensor and increasing the Hall voltage. As the fuel levels fall, so does the magnet, lowering the Hall voltage in parallel. 

Hall effect sensors are often used to time the speed of rotating parts like wheels and shafts, and are especially useful in various ‘tachometers,’ which measure things like vehicle speed and RPM, in addition to gauging fuel.

Hall effect sensors are especially effective in situations when optical and light sensors are impacted by things like water, vibrations, or dirt. Because magnetic fields cannot be disrupted by external influences, they are extremely useful in industrial applications.

Uses In smartphones

Hall effect sensors are being used in mobile phones and other mobile devices (such as tablets) to detect flip covers, which are commonly equipped with magnets.

The magnet is brought near the Hall sensor on your smartphone or tablet when the flip cover is closed. The magnetic field generated by the flip covers generates Hall voltage. When the Hall sensor detects this magnetic force, the mobile device can perform specific tasks such as turning off the screen using a Schmitt trigger in the circuit.

The battery life is extended by using a Hall effect sensor to disable the screen when it is covered and unable to be used.

Use In measurement

Hall effect sensors are commonly widely used to detect objects and spaces, but they can also be used to monitor current. The Hall Effect is based on the relationship between magnetic fields and currents, as stated at the start of this tutorial, with the devices listed above using magnetic fields to generate currents as an output.

You may also utilize a Hall effect sensor for current measurement by reversing the process and passing the current through a magnetic field.

Current sensors are necessary for monitoring equipment status, identifying possible fluctuations, and ensuring that the equipment is safe to use. While pressure switches, optical sensors, and zero-speed switches have all been used to monitor equipment in the past, measuring the current input can provide a more precise picture of its operation.

A digital or linear Hall effect sensor can be used to detect current since these devices are founded on the idea that a proportional magnetic field is produced for a given current flow.

One significant advantage of using Hall effect sensors for current measurement is that they are completely isolated from the voltage being monitored, making them a safe method of testing equipment without insertion. Digital Hall effect sensors are an excellent choice for current measurement because they are accurate and repeatable on both AC and DC power.

The Bottom Line

Hall effect sensors and switches are used in a wide range of applications, from current measurement to pressure sensors, fluid flow sensors, and object identification and these adaptable devices are an integral aspect of many electrical types of equipment. Hall effect sensors detect factors such as mechanical system closeness, speed, and displacement using magnetic fields. These sensors are non-contact, which means they don’t need to make actual contact with anything. Depending on their design and intended function, they can output a digital (on/off) or analog (continuous) signal.