The principle of the Hall effect

The Hall effect is a type of magnetoelectric effect, which was discovered by A.H. Hall (1855-1938) in 1879 while studying the conductive mechanism of metals. Later, it was discovered that semiconductors, conductive fluids, and other materials also have this effect, and the Hall effect of semiconductors is much stronger than that of metals. Various Hall components made from this phenomenon are widely used in industrial automation technology, detection technology, and information processing. The Hall effect is a fundamental method for studying the properties of semiconductor materials. The Hall coefficient measured through Hall effect experiments can determine important parameters such as the conductivity type, carrier concentration, and carrier mobility of semiconductor materials. The Hall effect in fluids is the theoretical basis for studying "magnetohydrodynamic power generation". According to the principle of the Hall effect, the magnitude of the Hall potential depends on: Rh is the Hall constant, which is related to the semiconductor material; IC is the bias current of the Hall element; B is the magnetic field strength; D is the thickness of the semiconductor material. For a given Hall device, Vh will depend entirely on the measured magnetic field strength B.

A Hall element generally has four output terminals, two of which are the input terminals of the bias current IC of the Hall element, and the other two are the output terminals of the Hall voltage. If the two output terminals form an external circuit, Hall current will be generated. Generally speaking, the setting of bias current is usually given by an external reference voltage source; If the accuracy requirement is high, the reference voltage source is replaced by a constant current source. In order to achieve high sensitivity, some Hall elements are equipped with permalloy with high magnetic conductivity on the sensing surface; This type of sensor has a high Hall potential, but saturation occurs around 0.05T, making it only suitable for use in low limit and small range applications. In recent years, due to the rapid development of semiconductor technology, various types of new integrated Hall elements have emerged. These types of components can be divided into two categories: linear components and switching components.

The principle of linear Hall elements

UGN350lT is a commonly used three terminal linear Hall element. It consists of a voltage regulator, Hall generator, and amplifier. It is very convenient to form a Gaussian meter using UGN350lT. Its use is very simple. First, make B=0 and record the indicated value VOH in the table. Then, place the probe end face on the tested object and record the new indicated value VOH1. Δ VOH=VOH1-VOH, if Δ If VOH>0, it indicates that the end face of the probe is measuring N poles; On the contrary, it is the S-pole. The sensitivity of UGN3501T is 7V/T, which can measure the corresponding magnetic induction intensity B. If digital voltmeter (DVM) is used, the linear Gauss meter shown in Figure 1 can be obtained. The operational amplifier adopts high-precision operational amplifier CA3130. The specific zero adjustment method of this circuit is: after turning on the power, set B=0, adjust W1 to make the DVM reading zero, then stick a standard neodymium aluminum boron magnetic steel (B=0.1T) on the probe end face, and adjust W2 to make the DVM reading 1V. If the displayed value of this Gauss meter during detection is -200mV, then the probe end face is detecting the S-pole, and the magnetic field intensity is 0.02T. The Gauss meter can also be used to measure the alternating magnetic field, but the DVM should be changed to an AC voltmeter. Obviously, using the circuit shown in Figure 1 can easily expand the functionality of an ordinary digital multimeter.

The UGN3501T can also be conveniently used to form a clamp type ammeter as shown in Figure 2. Place the Hall element in the gap of the clamp shaped cold rolled silicon steel sheet, and when there is current flowing through the wire, a magnetic field will be generated in the clamp shaped ring, which is proportional to the number of ampere turns of current flowing through the wire; This magnetic field acts on the Hall element, inducing the corresponding Hall potential, with a sensitivity of 7V/T, and passing through the operational amplifier μ A741 is zeroed, linearly amplified, and sent to DVM to form a digital clamp ammeter. The debugging of this table is also very simple: when the current in the wire is zero, adjust W1 and W2 to make the DVM reading zero. Then input a current of 50A and adjust W3 to make the DVM reading 5V; Reverse input -50A current, with a numerical value of -5V. By repeatedly adjusting W1, W2, and W3, the reading can meet the requirements. The clamp type ammeter has been tested and its sensitivity is not less than 0.1V/A. Similarly, the ammeter can also be used to measure AC current. It is very convenient to replace DVM with AC voltmeter.

Honeywell Sensor Applications and Applications in the Electric Bicycle Industry:

Hall sensors are widely used and have made significant contributions in many fields such as aviation and aerospace technology, medical technology, transportation, industry, measurement and testing. The current application field is relatively active in the field of electric bicycles. All of this is attributed to Honeywell's high-quality four Hall type components. Other high sensitivity Hall effect latches use dual or single Hall elements, which make them very sensitive to packaging stress, while four Hall elements make these sensors more stable and outstanding. These new high sensitivity latches are specifically designed for brushless DC motors. Its features include a wide temperature range, high sensitivity, compact design (available in SOT-23 and TO-92 packages for customers to choose from), bipolar latch type magnetic components (able to maintain stable performance throughout the entire temperature range), wide voltage range, built-in reverse voltage function, and materials that comply with ROHS standards. All of these excellent characteristics are crucial for brushless current motors in various industrial applications. Honeywell sensors are equipped with reliable high magnetic sensitivity switching points, and their Hall components do not use chopping stabilization technology. These characteristics possessed by Horney enable the sensor to output a complete signal, reducing the latch response time to 20 microseconds.

Electric Vehicle Control Experiment Diagram

Hall sensor for electric vehicle speed control knob

The speed control knob, as the name suggests, is the speed control component of an electric vehicle. It is a linear speed control component with many styles but the working principle is the same. It is generally located on the right side of an electric vehicle, in the direction of the right hand when riding, and the rotation range of the electric vehicle handle is between 0-30 degrees. Signal characteristics of the handle and brake handle: the form of the handle, signal characteristics, and signal modification.

The handle of an electric vehicle has three leads: the power supply (fine red+5V), the ground wire (fine black), and the handle speed control signal wire (continuous linear change signal fine green). There are two types of handlebars used in electric vehicles: photoelectric handlebars and Hall handlebars. Currently, the majority of electric vehicles use Hall handlebars. Common linear Hall element models include: AH3503 AH49E A3515 A3518 SS495. For example, the AH3503 linear Hall circuit consists of a voltage regulator, Hall voltage generator, linear amplifier, and emitter follower. The input is the magnetic induction intensity, and the output is a voltage proportional to the input quantity. The static output voltage (B=0GS) is about half of the power supply voltage. When the S magnetic pole appears on the marking surface of the Hall sensor, it will drive the output above the zero level; The N magnetic pole will drive the output below zero level; The instantaneous and proportional output voltage levels determine the magnetic flux density of the Z-sensitive surface of the device. Increasing the power supply voltage can increase sensitivity. Product features: small size, high accuracy, high sensitivity, good linearity, good temperature stability, and high reliability. The output voltage of the Hall knob depends on the strength of the magnetic field around the Hall element. Turning the knob changes the magnetic field intensity around the Hall element, which in turn changes the output voltage of the Hall knob.