Magnetic converters. Physical bases of the magnetic resistor magnetic resistor do it yourself
Magneticistor. is a semiconductor resistor, the main property of which is the ability to change its electrical resistance under the action of the magnetic field . Magnetic effect, or the Gauss effect is to change the specific conductivity of the semiconductor when the magnetic field affecting it is changed. The semiconductor plate is placed in an external transverse magnetic field, and the current is passed along it. The effect of the force of Lorentz causes the curvature of the charge carrier trajectory and leads to the elongation of the path passing by the carriers between the electrodes to which the external electric fieldthat is equivalent to increasing the resistance of the semiconductor. An increase in the resistance of the semiconductor occurs and when the magnetic field is directed perpendicular to the direction of the electric current flow, and when the direction of the magnetic field is parallel to the current direction. In the first case We are dealing with the transverse effect of magnetoresistance, which has received practical application. Second case Wears the name of the longitudinal effect of magnetoresistance. It did not find practical application due to a weak resistance change in the magnetic field. Magnetoresistance can be defined as a difference between the magnetic resistance of the magnetic resistor in the Magnetic field of the RV and without a magnetic field (initial resistance). The initial resistance R0 is determined by the material and the structure used. The factors affecting the magnetoresistance include the geometry of the semiconductor plate, the concentration and mobility of carriers
It is established that the magnetoresistance increases with a decrease in the rating length ratio to its width. The longer the path of the charge carrier in the semiconductor without collisions with other particles, the greater the flow of media is deflected. This means that electron mobility in the semiconductor plays an important role to increase resistance. Therefore, when using a magnetoresistive effect, materials characterized by high electron mobility are most often used.
One of the main characteristics of the magnetic resistor is the relationship RB \u003d F (B). This dependence (Fig. 7) at low magnetic induction is quadratic relative to B, and with large linear.
The characteristics of the magnetic resistor are highly dependent on temperature.
The dependence of the resistance of magnetorestors from the induction of an external magnetic field with various temperatures The environment is shown in Fig. 9. As can be seen from the figure, with an increase in the induction from 0 to 1T, the resistance at normal temperature changes approximately 6-12 times. Therefore, when using magnetoretors in a wide temperature range, it is necessary to provide for temperature compensation for their characteristics.
Magnetic resistors are used primarily in the measuring equipment; To measure magnetic induction, power, as a harmonic analyzer. Magneticallyistors are also used in frequency doubling schemes, converters direct current Variable, in the schemes of amplifiers and generators.
Magneticallyistors are also used as sensitive elements of contactless switches, linear displacement sensors, contactless potentiometers and in many other areas of electronic technology.
The main metrological characteristics of the magnetoresistors are the initial resistance R0, which lies in the range from the fraction of Ohm to tens of kiloma, and the magnetoresistive sensitivity Sb \u003d DR / DB. Usually, the dependences of ΔRB / r0 \u003d f (b) are used to characterize the magnetoresistive converters, where ΔRB \u003d RB-R0. The temperature coefficient of resistance of magnetic resistors (TKS) depends on the composition of the material, magnetic induction and temperature. The greater the sensitivity of the magnetic resistor, the greater its TKS. TKS values different types Magnetic resistors have the limits of 0.0002-0.012 K-1.
Magnetic resistors
The goal of the work is: to familiarize yourself with the physical principles of action, manufacturing technology, design and application of magnetic resistors, investigate their main characteristics and parameters
Magnetic Resistors (MR) – these are electronic components, the action of which is based on the change in the electrical resistance of the semiconductor (metal) when exposed to a magnetic field. MP used as magnetic sensors electric voltage Both current, speed and direction of rotation, in information reading devices in computer, in valve electric motors, magnetic field meters, etc. MR provide almost perfect mechanical, electrical, thermal, etc. Confusion of measuring and control circuits from control objects. They have speed, sensitivity, reliability, small dimensions and energy consumption. Currently known monolithic and film magneticallyistors.
The principle of operation of monolithic MR is based on the so-called magnetoresistive effect. As is known, in the semiconductor plate, which flows current, the Magnetic field occurs EMF Hall (Fig. 8.1.1)
E x \u003d k i b / b,
where I. - current flowing along the plate, B. - induction of the magnetic field, b.- wirina plate in the direction perpendicular to the current, K \u003d 1 / NE - the coefficient of the hall, e.and N. Accordingly, the elementary charge of current carriers and their concentration.
When establishing a dynamic equilibrium between the Lorentz force and the power of the Hall electric field, charge carriers having the same speed v. will move along straight trajectories in the direction of external electric current, while the vector of the total electric field is directed to the current vector through the semiconductor at some angle φ. The angle of the Hall is determined by the formula: tG Φ \u003d e x / e \u003d u bwhere u-the mobility of charge carriers. With small magnetic fields and, therefore, small corners of the hall φ ≈ U b.
When establishing a dynamic equilibrium, the Halolian electric field strength compensates for the effect of the Lorentz force, and, therefore, it does not curve the trajectory of charge carriers having the same speed v. It would seem, in this case, the resistance of the semiconductor should not be changed under the action of the magnetic field.
In fact, the carriers in the semiconductor are subject to a certain distribution of speeds. Therefore, the carriers with a speed exceeding the average speed, and carriers having a speed smaller compared to the average, are shifted to different points on the side verge of the semiconductor plate, since they act on the magnitude of Lorentz. Thus, the resistivity of the semiconductor in the magnetic field changes due to the curvature of the trajectory of charge carriers moving at a speed other than the average speed.
The largest magnetorezistive effect can be obtained in a semiconductor of such a form and design, in which the occurrence of the Hall tension of the electric field is difficult or impossible. These conditions are theoretically can be implemented in a semiconductor plate with infinitely large dimensions in the direction perpendicular to the external electric field strength. In such a semiconductor, there is no accumulation of charge carriers on the side of the side, the emf of the hall is not formed, and the charge trajectory deviates from the direction of the external electric field in the direction of the Lorentz force (Fig. 8.1.2). The current density vector coincides in the direction of charge carriers and therefore turns out to be shifted relative to the external electric field strength vector at the Hall Angle φ . The deviation of the trajectory of charge carriers in an unlimited semiconductor is equivalent to a decrease in the length of the free path of charge carriers in the direction of the electric field on,
here L 0.- the length of the free range of charge carriers in the absence of a magnetic field, L.- The projection of the charge path passed by the carrier between two successive clashes in the presence of a magnetic field into the direction of the external electric field. At small COS Hall Corners φ can be decomposed in a row
cos. φ = 1- Φ 2/2! + ...
then ΔL ≈ L 0 - L 0 + L 0 φ 2/2, and therefore ΔL ≈ L 0 φ 2/2.
Since during the free run, the charge carrier passes in a magnetic field a smaller way along the electric field , this is equivalent to a decrease in drift velocity and mobility and, therefore, the specific conductivity of the semiconductor., Relative change in the resistivity is at the same time. (ρ - ρ 0) / ρ 0 \u003d ΔL / l 0 \u003d u 2 b 2/2.
For limited by its semiconductor crystal, the ratio is true Δρ / ρ 0 \u003d C u 2 b 2where FROM - The coefficient depending on the shape of the semiconductor plate.
Recently, a film MR film was distributed, the magnetically sensitive element of which serves a ferromagnetic film (nickel alloy with cobalt or nickel and iron). The operation of the film MR is based on an anisotropic magnetoresis effect, which consists in the fact that the outer magnetic field changes in ferromagnetic material the likelihood of electrons scattering in different directions, which, in turn, leads to a change in electrical resistance.
Magnetic resistors- These are resistors of alternating resistance, the value of which depends on the tension of the applied magnetic field.
The magnetic detector is a semiconductor plate, the surface of which metal strips are applied (Fig. 7.14). Each part of the semiconductor plate between the two metal stripes is a separate magnetic resistor. Metal strips perform the role of shunts that reduce the EMF Hall, arising on the lateral edges of the semiconductor plate.
The main semiconductor material for magnetic resistors is India Antimid Insbi Arsenide IndiaInas- materials with large electron mobility (7.6 m 2 / (in · c) and 3.3 m 2 / (in · c), respectively). The domestic industry is produced by Magnetic studies of typeMR, see Their characteristics: nominal resistance 50 ... 220 ohms, scattered power 0.15 ... 0.25 W.
M. 
agnitodiodions(Fig. 7.15, but) - These are the diodes with a thick base, the resistance of which increases in a transverse magnetic field as a result of a decrease in the mobility of the main and non-core charge carriers, as in the usual magnetorette. An increase in the diode resistance of a diode with a thick base may also be associated with a decrease in the lifetime of non-core carriers, if, due to the curvature of the trajectory of motion, the non-core carriers will reach the surface of the base area, where the speed of their recombination is large. As a material for the manufacture of magneticodiodes, single crystal germanium or silicon, having a fairly greater mobility of charge carriers. The straight branches of the Germany magnetic cells in magnetic fields with different magnetic induction are shown in Fig. 7.15, b..
To estimate the sensitivity of the magnetot to the magnetic field, by analogy with the hall converters, use volt sensitivity, the expression for which is specified as
, B / (TL · a), (7.29)
where Δ. U.- change in voltage on the magneticodyode when making it in a magnetic field, in; I. etc - the value of direct current, and; IN- The value of magnetic induction, TL.
Volt sensitivity of magnetodiodes can be significantly higher than the voltage sensitivity of the hall converters from the same material.
M. 
agnecial sensors.Anisotropic magnetic resistivity (AMR) Sensors are special resistors made from a thin permalloe film placed on a silicon plate (Fig. 7.14). In their production, the film is placed in a strong magnetic field for the orientation of magnetic areas in the same direction, thereby determining the direction of the magnetization vector. Then, when hitting the outer magnetic field, perpendicular to the film, the magnetization vector starts to rotate or change the angle. This, in turn, changes the resistance of the film. The magnetic field converter consists of four thin-film magnetoresistors R.1-
R.4
(Fig. 7.16) connected to the bridge circuit.
Changes in the resistance of magnetic resistors in the adjacent shoulders of the bridge circuit are opposite by the sign when exposed to the magnetic field of one polarity (the change in the resistance in Figure 7.16 is conditionally depicted by symbols "+" and "-"). At the same time, the amount of changes to the resistance of the shoulders depends on both the value and polarity of the induction of the affecting field, and on the angle between the induction vector INand the plane of the magnetically sensitive element. Resistance change can be detected by changing the output voltage U. Out, and then calculate the power of the impact magnetic field. Thus, the converter has a coordinate sensitivity of relatively two mutually perpendicular planes.
Magnetic resistor sensors are miniature in size and placed on a substrate with dimensions of about 5 × 4.5 mm. The relative magnetic sensitivity of magnetic sensors is 1 ... 27 (MKV / B) / (A / m); supply voltage U. P \u003d 5 ... 10 V with current consumption no more than 10 mA. Such low-power sensors can be released either separately or built into other products. With proper calibration, electronic compasses on magnetorevatory sensors can reach accuracy exceeding one degree. Built-in compasses in some GPS receivers are based on this technology.
Control questions and exercises
1. Explain the essence of the Seebeck effect.
2. List the components of the thermoem.
3. How is the thermobature?
4. Explain the principle of the thermal pump.
5. Causes of the appearance of the Thomson effect.
7. Display an expression for EMF Hall.
8. Device and basic parameters of the hall converter.
9. What is the volt sensitivity of the Hall transcender?
10. Explain the principle of operation of the bipolar magnetotransistor.
11. What is the magnetic effect?
12. What is the corner of the Hall and what does it depend on?
13. What kind of design should magnetoretors?.
14. Which diodes can be used as magneticodiodes?
Contacts
Neutral 215.
Coefficient
Peltier 219.
Hall 225.
Lorentz, power 224
Magnitodiode 231.
Magneticallyistor 230.
Magnetic resistor sensor 232.
Magnetotransistor 228.
Heat 221.
Hall Converter 226.
Term Battery 216.
ThermoDes 216.
Hall angle 229.
Seebek 216.
Magnetoresistive 228.
Peltier 219.
Thomson 222.
Fig. 1. Connection diagrams of magnetic resistors to the power supply and load, and is single with RN; b - Differential (half-litost); B - differential in the bridge scheme; G is a magnetorevoyistor bridge.
To compensate for the thermal instability of a single magnetic sistor, you can use a specially selected (TCC) thermistor, which is turned on instead of the load resistor RN (Fig. 1a).
The best results gives the use of differential magnetoresistors (Fig. 1b, c) and magnetically systemic bridges (Fig. 1g).
To enhance and primary processing of the signal, "removable" from the magnetic resistor, various electronic circuits, made on transistors (Fig. 2.) or integral chips (Fig. 3, 4), can be used. In fig. 2.A The diagram of the input cascade of the magnetoelectronic device, made on the magnetoresistor, is shown.
Fig. 2. Schemes for switching on the magnetic resistor into the transistor cascade.
When exposed to the magnetic degree R1 of the external magnetic field, the signal at the output of the chain R1 - R2 changes in proportion to the change in the magnetic field strength and within the linear portion of the input characteristics of the VT1 transistor. The mode of operation of the transistor is set by the R2 resistor. This circuit uses a transistor with the maximum possible static current transmission coefficient (more than 200).
The scheme (Fig. 2b) is complemented by a key cascade on the VT2 transistor, immersed on the relay K1.
To enhance the signal of magnetoresistors when creating modern magnetoelectronic devices, it is most advisable to apply operating amplifiers, included according to the scheme of resistance-voltage type converters (PSN).
As part of highly sensitive magnetoelectronic devices, the use of low-noise integral instrumental amplifiers of the AMR-04 and AMR-01 type (Analog Devices) or INA118P (BurrBrown) is the most efficient.
Increasing the thermal stability of magnetoelectronic devices is ensured by using special thermostat and nutrition schemes from the AC source.
In fig. 3a As an example, the power schemes and thermostabilization of the operation mode of the thin-film magnetorevator type GMR Sat. In this case, the amplification of the signal can be carried out by the amplifier, the diagram of which is shown in Fig. 3b.
Fig. 3. Power schemes and thermal stabilization of the mode of the T-film magnetic genetic system of type GMR C6 using: A - Posistor; B - signal amplifier.
At the value of the resistor R6 \u003d 5k, the gain coefficient of such a scheme is approximately 18.
In fig. 4 and 5 are the simplest schemes for connecting magneticallyistors to operating and tool amplifiers.
Fig. 4. Scheme of amplification of the signal of a thin-film magnetic system bridge recommended by Siemens A. G.
Fig. 5. The inclusion scheme for a differential "monolithic" magnetorestor, recommended by Siemens A. G.
In fig. 5 shows the scheme for the inclusion of a differential "monolithic" magnetic resistor, designed to work in a device for controlling the speed of rotation of the gear wheel.
In fig. 6 is given a scheme for inclusion of a thin-film magnetically system of type KMZ10, designed to register weak magnetic fields.
Fig. 6. The scheme for inclusion of the KMZ10 thin-film magnetorestor, designed to register weak magnetic fields.
The diagram shown in Fig. 6, ensures the following features:
compensation of sensitivity drift depending on the temperature through the feedback loop, which includes a KTY 83-110 thermistor;
adjustment of offset with the resistor R8;
adjusting the sensitivity of the circuit using a multi-turn resistor R4.
The diagram shown in Fig. 7, it can be used as in a linear (DA1 functions as a voltage amplifier) \u200b\u200band in "digital" (DA1 is used as a comparator) modes. Modes of operation are installed by trimming resistors R1 and R2.
Figure 7. The inclusion scheme of the thin-film magnetic bridge of the NMS1001 recommended by Honeywell.
Ohoho, so I got to alterations on Hall Sensorsyour joystick - Trustmaster Topgun Afterburner II. Despite the fact that the experience of the "Runet" is already available, I will tell you again, what should I do :)
In principle, everything that will be discussed below applies to almost any joystick, and not just to our experimental.
History of the problem
If someone is in the tank, then I explain: almost all the joysticks, especially past years of release, was made on the basis of trickening resistors who, by virtue of their constructive features And even more active use in the joystick quickly came into disrepair and managed the aircraft was not comfortable, he simply did not obey Rus. And then it was invented to use the Hall sensors instead of mechanical resistors. Industrial models appeared, but they are extremely small. And then the folk craftsmen became their own hands to redo the sensors of the Hall Joystick. And these sensors are beneficial to the mechanical resistors in the fact that they do not have the most mechanical parts and do not fail for the same reasons because they work on a magnetic field if it can be expressed.The Magnetoelectric Hall Sensor received its name named E. Hall, American Physics, which opened in 1879 an important galvanized phenomenon. If the semiconductor, according to which (along) flows the current, affect the magnetic field, then there is a transverse difference of potentials (EMF Hall). In other words, the sensor changes resistance depending on the direction and magnitude of the magnetic field. This we use.
Go
For all alterations, we will need:
- Two SS495 Hall Sensor (A) or SS496 (A)
- Two neodymium magnets
- Two small self-pressing / screws
- Wiring for soldering
- Termoklay
So, first must prepare the joystick. You have to pull the resistors and cut their fasteners. To do this, unscrew the pressure cover of the spring with Rus (it will move freely, it will be more convenient to twist everything in your hands), unscrew the 4 screw screws of the entire block, drop the wires from the resistors and pull the resistors themselves. Also cut off the place of fastening of resistors, they will no longer need, besides, they will interfere with the installation of sensors and magnets.
Just necessarily, before unsoldering the wires from the resistors, find out where they have food, and where signal (O) wire. I was guided by the image on the right, it turned out to be faithful. But you can not trust him and check yourself: we touch in one probe multimeter of the bare wire, which is available in the cable connecting the joystick with the connectorUSB - this is a housing, and the other probe touch any extreme output of resistors if it shows +5V or just 5 V (Well, it may be a little less), then you have found a power wire, and if about 0v, then this is the contact of the housing (-). The remaining third contact of the resistor and will be signal.After you find out where what wires, it's time to solder the Hall sensors. Sold out the signal wire to the signal contact of the sensor, but the power to the sensor is a bit different. Those wires that feed resistors can cut off from their places
and use to power the sensor, having sold them to the specified USB + and USB contacts
Now the check time has come. Run the JoyTester program, plug the joystick to the PC, and, bringing magnets to the sensors, look at the schedule in the program. If he reacts to your movements with magnets relative to the sensors, then you soldered everything right and they work.
Magnets. It happened that I did not have old CD / DVD drives, and when I purchase, I got round magnets, but it is not scary. I fastened them into small screws (right on the side face of the hats), pre-rooting. It was necessary to shorten them, otherwise they screwed up too deep and threw the moving nodes in the Rus mechanism. I bite off the unnecessary in the screws with simple laying on the metal, slapping the hammer on them. You can additionally drop the thermoclause into the hole of the axis, where you will screw the screws, because My slightly dangled there. In the case of rectangular magnets, they are better to mount on the "main plane" of the hats, and round - on the end of the hat (in my case). After screwing the screws, tighten the cover of the clamp of the spring Rus until it stops so that Rus gets the most vertically as possible.
Here, actually, and that's it! Magnets hung, the sensors were glued, calibrated - you can in the sky! On the extrusion, in any airlimulator there is a software setup of the axes, it will be possible to twist them in terms of the situation.
