Hall Effect Sensors are magnetic field sensors made based on the Hall effect. When a constant current flows through the internal Hall semiconductor chip, a potential difference, known as Hall voltage, is generated in the perpendicular direction. This Hall voltage changes with the strength of the magnetic field; the stronger the magnetic field, the higher the voltage, and the weaker the magnetic field, the lower the voltage. Although the Hall voltage is very small, usually only a few millivolts, it is sufficient to output a strong signal after amplification.
Figure 1. Principle of Hall Sensor
Hall sensors are divided into linear Hall sensors and switch-type Hall sensors. They share common characteristics such as sturdy structure, small size, light weight, long lifespan, easy installation, low power consumption, high frequency (up to 1MHz), vibration resistance, and resistance to dust, oil, moisture, and salt mist contamination or corrosion.
Hall sensors are passive sensors and require an external power supply to operate. This feature allows them to detect low-speed operation, and they are widely used in frequency speed adjustment devices, inverter devices, UPS power supplies, inverter welding machines, electroplating, CNC machine tools, microcomputer monitoring systems, power grid monitoring systems, and various fields requiring isolated detection of current and voltage, to measure physical quantities such as speed, acceleration, angle, angular velocity, number of revolutions, rotational speed, and time changes in operational status.
Linear Hall Sensors
Linear Hall Sensors consist of Hall elements, linear amplifiers, and emitter followers. They output analog signals with high accuracy and good linearity, primarily used for measuring AC and DC currents and voltages.
Linear Hall Sensors can convert large primary currents into small secondary voltage signals. For example, the ACS712 current sensor mainly consists of a copper current path near the chip surface and an accurate low-offset linear Hall sensor circuit, which can output a voltage proportional to the detected AC or DC current. The internal resistance of the current path (between pins 1 and 2, 3 and 4) is typically 1.2mΩ, resulting in low power consumption. The insulation voltage between the current path and the sensor pins (pins 5-8) is >2.1kVRMS, making it nearly insulated. The magnetic field generated by the current flowing through the copper current path can be sensed by the on-chip Hall IC and converted into a proportional voltage.
Figure 2. Functional Diagram of ACS712 Linear Hall Sensor
The ACS712 features low noise, fast response time (the output rise time for step input current is 5μs), and a maximum total output error of 4%. It has high output sensitivity (66mV/A to 185mV/A) and is mainly used in motor control, load detection and management, switch-mode power supplies, and overcurrent fault protection, particularly in applications requiring electrical insulation without using opto-isolators or other expensive insulation technologies.
Figure 3. Typical Applications of ACS712 Linear Hall Sensor
Switch-type Hall Sensors
Switch-type Hall Sensors consist of voltage regulators, Hall elements, differential amplifiers, Schmitt triggers, and output stages. They output digital signals and feature contactless operation, no wear, clear output waveforms, no jitter, no bounce, and high position repeatability.
Figure 4. Internal Structure of A3144 Hall Switch Sensor
For example, the A3144 Hall Switch Sensor consists of a voltage adjustment circuit, an inverse power protection circuit, a Hall element, a temperature compensation circuit, a signal amplifier, a Schmitt trigger, and an OC gate output stage. By using a pull-up circuit, its output can be connected to CMOS logic circuits. The A3144 can detect a specific pole on each side, features contactless operation with no sparks in the switch state, produces no interference, has a long lifespan, and high sensitivity. Its transistor logic can easily interface with MCUs. Since it has a digital output, it means that if a magnet is detected, the output will be low; otherwise, it remains high.
Figure 5. Application Circuit of A3144 Hall Effect Sensor
Hall Switch Sensors are simple to apply. Apart from the A3144 Hall Effect Sensor, only a 10K ohm pull-up resistor and a 0.1uF noise filtering capacitor are needed.
Interface with Arduino UNO
The interface between Hall Sensors and Arduino UNO is not complicated. However, note that the linear Hall sensor with analog output requires independent power supply and cannot draw power from the Arduino UNO. Meanwhile, the signal pin should be connected to the Arduino’s analog pin (commonly A0).
Figure 6. Comparison of Switch-type (left) and Linear Hall Sensors (right) Interface with Arduino UNO
Digital output switch-type Hall Sensors are used to detect states; simply connect the signal pin to any digital pin on the Arduino, and the sensor can read the data.
Author: Hard City Allchips, Source: Breadboard Community
Link: https://mbb.eet-china.com/blog/uid-me-3975615.html
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