Weak current College】 【Hall sensor components and application】.

<br> 1, Introduction to the Hall device is a magnetic sensor.. They can be detected by the magnetic field and its changes, in various situations related to the use of the magnetic field.. Hall devices based its work on the Hall .effect.. Hall devices have many advantages, their solid structure, small size, light weight, long life, easy installation, low power consumption, high frequency (up to 1MHZ), resistant to shock, not afraid of dust, oil, moisture and .salt spray, etc.. contamination or corrosion.. Hall of linear devices, high precision, good linearity; Hall switch device without contact, no wear, the output waveform clear, jitter-free, no bounce, position repeatability of high (up to .μm level).. Access to a variety of compensation and protective measures the Hall device operating temperature range, up to -55 ℃ ~ 150 ℃.. Hall devices in accordance with the functions they can be divided into: Hall-Hall-linear devices .and switching devices.. The former analog outputs, which output digital content.. According to the nature of the object to be detected can be divided into their applications: direct application and indirect application.. The former is directly detected by the test object itself .or the magnetic properties of the magnetic field, which is to test subjects on the artificial magnetic field of an object, use this field to be detected in the information carrier, through which the number of non-electric, non-magnetic. physical quantities such .as force, torque, pressure, stress, position, displacement, velocity, acceleration, angle, angular velocity, rpm, speed, and work status change time, into power to detect and control.. 2, Hall effect and Hall 2.1 Hall effect device .shown in Figure 1, in a power semiconductor thin, coupled with the magnetic field perpendicular to the surface and the film B, the lateral sides of the sheet there will be a voltage, as shown in Figure .1 of VH, this phenomenon is the .Hall effect, by scientists love German? Hall discovered in 1879.. Known as the Hall voltage VH.. This phenomenon arises because the power semiconductor film carrier in the magnetic field generated by the action of Lorentz force, respectively, on both sides of the .horizontal deflection of the film and accumulate, creating an electric field, called the Hall electric field.. Hall electric field generated by electric force and the Lorentz force the contrary, it prevents the carrier continue to pile up until the Hall electric field force and Lorentz .force are equal.. At this time, the film on both sides to establish a stable voltage, this is the Hall voltage.. For the four electrodes on the film, in which C1, C2 to work through the current inter-I, C1 ., C2 as current electrodes, C3, C4 out between the Hall voltage VH, C3, C4 called sensitive electrode.. On the various electrodes welding wire, and encapsulated with plastic film to form a complete Hall element (also known as the Hall). .. In the above (1), (2), (3) where VH is the Hall voltage, ρ is the material used to make the Hall element resistivity, μn is the electron mobility of the material, RH is the Hall coefficient, l .., W, t are the Hall element of the length, width and thickness, f (I / W) is the geometric correction factor is determined by the geometry and dimensions of components of decision, I was working current, V is between two current .electrodes. voltage, P is a component of power dissipation.. By (1) to (3) can be seen, in the Hall component, ρ, RH, μn depends on the component materials used, I, W, t and f ( .I / W) depends on the device design and process, Howard. Seoul components once made, these parameters are constants.. Thus, equation (1) to (3) represents the work of the three Hall elements results.. (1), .said current drive, (2) the voltage-driven, (3) can be used to evaluate the Hall can afford the maximum power.. In order to accurately measure the magnetic field, common constant current source power supply, so that a constant operating .current, therefore, measured the magnetic flux density B can be used to measure the Hall voltage.. In some precision measuring instruments, also use incubators, which will be placed in the Hall element, so RH is constant.. The use of environmental temperature .changes, often driven by constant pressure, and the RH for comparison, μn relatively flat with temperature, and thus subject to temperature changes VH small.. In order to obtain the highest possible output Hall voltage VH, can increase the operating current, while the .power consumption of components will also increase.. (3) expressed the VH can reach the limit - the maximum power dissipation components can withstand.. Hall 2.2 Hall devices into the device: the Hall element and the two major categories of Hall IC, the .former is a simple Hall films, often needs to be obtained using the Hall voltage amplification.. The latter will be the Hall and its signal processing circuitry integrated on the same chip.. 2.2.1 Hall element semiconductor Hall element can be a variety of .materials, such as Ge, Si, InSb, GaAs, InAs, InAsP, and multi-quantum well semiconductor heterostructure materials and so on.. InSb and GaAs Hall element output characteristics shown in Figure 1 (a), Figure 1 (b). .(A) Hall effect and the Hall element <BR> (b) InSb Hall element output characteristics <BR> (c). The output characteristics of GaAs Hall element <BR> Figure 1 The structure and the Hall element output characteristics .of the Hall element is used extensively for measuring the magnetic brushless DC motors and instrumentation.. 2.2.2.1 Hall-linear circuit which consists of the Hall element, the differential amplifier and emitter follower composition.. The output voltage on the Canadian in the Hall .element is proportional to the magnetic induction intensity B, and its functional block diagram and output characteristics are shown in Figure 2 and Figure 3.. Hall-linear circuit in Figure 2 a functional block diagram in Figure 3 Hall <BR> linear circuit UGN3501 .the magnetic conversion characteristic curve of this type of circuit has a high sensitivity and excellent linearity for a variety of magnetic field detection.. Hall-linear circuit performance parameters in Table 3.. 2.2.2.2 Hall switch circuit switching Lu Huoer Hall, also known .as digital circuits, the voltage regulator, Hall-film, differential amplifier, Schmitt trigger, and output stage components.. The role of external magnetic field, when the magnetic flux density than the threshold turn-BOP, the Hall circuit output tube conduction, .the output low.. Later, B to increase, remain on-state.. If the B value of the magnetic field reduced to BRP, the output MOSFET is off, output high.. We call for the working point BOP, BRP for the .release point, BOP-BRP = BH called back to the poor.. The existence of hysteresis switching circuit enhanced anti-jamming capability.. Hall switch circuit function box shown in Figure 4.. Figure 4 (a) that open collector (OC) .output, (b), said dual output.. Their output characteristics shown in Figure 5, Figure 5 (a) that ordinary Hall switch, (b) locking said Hall switch output characteristics.. <BR> <BR> (A .) single-OC output (b) double-OC output Hall switch circuit in Figure 4 <BR> functional block diagram of <BR> (a) switch-type output characteristics (b) output characteristics of locking <BR>. .Figure 5 The output characteristics of the Hall switch circuit generally provides that when the applied magnetic field of the Antarctic (S pole) to play the shell near the Hall-circuit side of the logo, the role of the Hall <BR> Seoul magnetic .field direction on the circuit is positive, the Arctic. close to the sign face is negative.. Locking switch circuit is characterized by the Hall: When the external field B positive increase, to BOP, the circuit turns on, then either increase or decrease .B, and even B removed, the circuit maintains on-state, only to negative. the BRP, the only change for the cut-off state, which is called locking.. 2.2.2.3 differential Hall circuits (two Hall circuit) it by .a pair of Hall-voltage generator 2.5mm away from the Hall element, whose functional block diagram shown in Figure 6.. Figure 6 Differential Hall of the circuit schematic circuit back in place when using a permanent magnet, when the gear is made of ferromagnetic .materials, turned around from the circuit when a pair of Hall, the Hall voltage generated on-chip phase-contrast, the. differential amplification, the device greatly improved sensitivity.. Made with this vehicle gear sensor circuit has a very excellent performance.. .2.2.2.4 Other than the above-mentioned Hall Hall circuit devices, but currently there have been many special features of the Hall circuit, such as power Hall-circuit, multi-wire Hall sensors.. 3 Application of Hall devices 3.1.1 3.1 .applications in general test measuring magnetic field using the method of Hall device is very simple, the Hall devices made of various forms of the probe, on the measured magnetic field, Yin Huoer device only. on the surface perpendicular to the Hall sensitive to magnetic induction ., which must be made perpendicular to the surface magnetic field lines and devices, is powered by the output voltage can be measured intensity of the magnetic induction.. If vertical, the vertical component should be obtained to calculate the measured values of the magnetic flux density ... Moreover, Yin Huoer extremely small size components, can be multi-point detection, data processing by a computer, you can get the distribution field, and on the slit, the magnetic field to detect holes in the work of the magnet settings 3.1 ..2. with the magnetic field, as was sensing movement and position of objects when the information carrier, the general work of the permanent magnet to generate a magnetic field.. For example, a 5 × 4 × 2.5 (mm3) No. Ⅱ .NdFeB magnet, its poles can be obtained on the surface of about 2300 gauss magnetic field.. In the air gap, magnetic flux density will decrease rapidly with increasing distance.. To ensure the Hall device, in particular the work of Hall and reliable switching .device, to be considered in the application of effective working air gap length.. Work in calculating the total effective air gap, the surface should be counting hall.. The sealed hall circuit, the depth of the Hall will be given in the product manuals ... Hall devices need to work because of power or position in the sensor for movement, generally so that the movement of objects to be detected with the magnet, the Hall device is fixed in the appropriate place in the work system, work with it to .detect the magnetic field, and then the results from the test. extract the information were seized.. Work between the magnet and the movements of the Hall devices are: (a) of the shift; (b) lateral; (c) rotation; .(d) interdiction.. Shown in Figure 7, the figure is the total effective working air gap TEAG.. <BR> <BR> Figure 7, the work of Hall devices and the movement between the magnet means in Trip mode, .magnet and Hall devices work in an appropriate gap is relatively fixed, with a soft (such as soft iron) as the movement of work wing. components, when the wing into the gap, the role of the Hall devices are magnetic field lines on some .or all of interdiction as a way to adjust the working magnetic field.. Sensing the motion information is added on the wing.. High precision of this method in the temperature range 125 ℃, the wing position repeatability of up to 50μm.. < .BR> <BR> Figure 8, the magnet placed in the back of the Hall device can also work the back of the magnet fixed to the Hall device (the shell did not hit the side of the sign), so that the seizure of .the ferromagnetic objects (such as steel gears) from their. near by, to detect the distinctive marks on objects (such as teeth, flange, notch, etc.), draw the object motion parameters 3.1.3 The interface with the external circuit Hall .switch circuit in the output stage is usually an open collector NPN. transistors, the use of rules and any similar NPN switch the same.. Output tube end, the input leakage current is very small, usually only a few nA, can be ignored, .the output voltage and its power supply is similar, but the power supply voltage may not exceed the breakdown voltage of the output tube (ie, the limit stated in the table specification voltage).. Conducting output transistor, its output and common line short circuit ... Therefore, we must add a resistor (that is, the load resistor) to limit the current flowing through the pipe so that it does not exceed the maximum allowable value (typically 20mA), so as to avoid damage to the output tube. .. Output current is larger, the tube saturation voltage also increases, the user should pay special attention, and you only want to control the voltage cut-off voltage of the circuit (or logical "zero") is compatible.. To interface with .the light-emitting diode, for example, the choice of the load resistor for an estimate.. If Io is 20mA (Hall-circuit output tube to allow aspiration of the maximum current), light-emitting diode forward voltage VLED = 1.4V, .when the supply voltage VCC = 12V, the required load resistor values (4). and the resistance of the nearest standard resistance 560Ω, therefore, desirable 560Ω resistor as the load resistor.. Figure 9 that simplifies the use of the Hall switch circuit, .Figure 10 shows the interface with a variety of circuits: (a) and TTL circuits; (b) and CMOS circuits; (c) and LED; (d) and SCR.. <BR> <BR> Figure 9 a simplified .diagram of the Hall switch <BR> Figure 10 Hall switch and circuit interface for example interface with the circuit load resistor value required for the estimation methods, and (4) method. the same.. If the controlled circuit is greater than the current .required to 20mA, can be charged in the Hall switch circuit between the access circuit and current amplifier.. Hall devices is greater than the switching current needed to 20mA, can be in the Hall switch circuit between the access circuit and current amplifier.. Hall .effect device switches very quickly, typical rise and fall time 400nS range, better than any mechanical switches.. 3.2 The following examples will give some examples.. Examples of such applications is only one kind of the same principles and methods, the user can use .their own needs, design their own appliances.. 3.2.1 Detection of magnetic devices used for the linear Hall probe, measure 10-6T ~ 10T alternating and constant magnetic field, there are many commodity instruments.. Here, only describes a calibrated UGN3503 .or A3515 Hall effect linear circuits to detect the magnetic flux density of simple methods.. Circuit factory, the factory can provide the calibration curve of each circuit block and sensitivity coefficients.. Measurement, the circuit first leg (from left to right sign face to .face number) then the power, the second leg grounded, then the third foot high input impedance (> 10kΩ) voltage meter, power, will be placed in the circuit under test. magnetic field, magnetic field lines perpendicular to the surface of the .circuit, reading out the value of the voltmeter, you can check on the calibration curve obtained from the corresponding magnetic flux density values.. Before use, the device is powered on for a minute, so as to achieve stability.. Measured by the sensitivity .coefficient value of the magnetic field B, can B = [Vout (B)-Vout (o)] 1000 / S where, Vout (B) = the measured magnetic field with the voltage readings in V., Vout (o) = the .measured magnetic field does not increase the voltage readings in V, S = sensitivity coefficient, in units of mV / G (Gauss), B = intensity of the magnetic induction measured in units of G. .3.2.2 Detection of ferromagnetic objects in the .back-biased Hall-linear circuit of a permanent magnet, shown in Figure 11.. Figure 11 (a) denotes the gap ferromagnetic objects, Figure 11 (b) denotes that the gear teeth.. They are connected in the circuit shown in Figure .12, (a) for the detection of gear, (b) for the detection gap.. This method can detect the gear speed.. <BR> 3.2.3 used in the DC brushless motor DC brushless motor with permanent magnet rotor, .place the appropriate place in the stator the required number of Hall devices, their output and the corresponding power supply circuit connected to the stator windings.. Near the rotor through the Hall device, the permanent magnet rotor of the magnetic field so that the device has .power output of the Hall voltage to the stator windings of a power supply circuit turns on power to the appropriate stator windings, and rotor magnetic field produced the same magnetic field polarity., repulsive rotor continues to rotate.. To the next location, the former .location of the Hall device to stop working, the next bit of the Hall device conduction, so the next winding is energized, resulting in repulsion field causes the rotor to continue turning.. This cycle, maintaining the motor work.. Its working principle is .shown in Figure 13.. Here, the Hall effect device from the position sensor to detect the rotor magnetic pole position, its output power supply circuit to the stator windings off, switch the role was underway, when the rotor poles away, so stop working .on a Hall device., the next device to work, so that the rotor magnetic pole is always the face of repulsion, the Hall device was underway for the role of the stator current.. Brushless motor in the Hall device, either using the Hall .element, can also use the Hall switch circuit.. When using the Hall element, generally an external amplifier circuit, shown in Figure 14, using the Hall switch circuit can directly drive the motor windings, greatly simplified the circuit shown in Figure 15.. .Figure 15, latch circuit hall switch with the CS2018 to directly drive the motor circuit diagram <BR> (the figure for the stator coil windings) edited: Zhang houses..