SU1458969A1 - Contactless switch - Google Patents

Abstract

The invention relates to automation and can be used in electronic systems for tracking the position of an object, for example, in track switches, emergency control devices, etc. The aim of the invention is to expand the functionality of the device, namely increasing its range and expanding the range of variation of the magnitude of the course, by using the key mode of the bipolar transistor, which allows you to independently set the position of the device on and off points and the value of the path differential. The goal is achieved by introducing into the active element of generator 1 of magnetoelectric oscillations an additional bipolar transistor 7 and a second drosel 8. The switch also contains a loop winding 2, a feedback winding 3, a loop capacitor 4, a first choke 6, a ferrite core 9. Jacks 10 and 11 Oscillator 1 is connected to the capacitor plates 12 of the filter. 2 Il. cl

Description

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The invention relates to automation and can be used in electronic systems for tracking object location, for example, track switches, emergency control devices and object security devices.

The aim of the invention is to expand the functionality of a contactless switch, namely, increasing the range of its operation and expanding the range of variation of the stroke differential (width of the hysteresis loop when the contactless switch is turned on and off) by introducing an additional parallel circuit in the active generator of the oscillator. a bipolar transistor with a choke in the emitter circuit, and using the key mode of the bipolar transistor, which allows independently set the position of the on-off point of the proximity switch (work distance value) and the value of the travel differential.

FIG. 1 is a schematic diagram of a proximity switch; FIG. 2 shows the dependence of the output bus current on the position (gap) of the ferrite core and the test object at different values of the inductances of the first and second throttle circuits of the autogenerator.

The contact switch contains an oscillator 1 of magnetoelectric oscillations, consisting of series-connected loop winding 2 and feedback winding 3, loop capacitor 4, field-effect transistor 5, first drossel 6, bipolar transistor 7, second drossel 8 and ferrite core 9. Viewers 10 and 11 of the autogenerator are connected to the plates of the capacitor 12 of the filter and the pin 13 of the power supply and the output bus 14, respectively.

The self-oscillator 1. is made according to the inductive three-point scheme using as an active element parallel-connected field 5 and bipolar 7 transistors, the source and emitter of which, respectively, are connected to the connection point of windings 2 and 3 and one of the contours via the first and second 8 respectively.

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the capacitor 4, the gate and the base are connected to the combined second inlets of the loop winding 2 and the loop terminal of torus 4, and the drain and collector are connected to one of the terminals 10 of the autogenerator 1. The second feedback winding terminal 3 is connected to the second gate 11 Oscillator 1.

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The control object is located at some distance from the end face of the core 9 I and, depending on this distance, introduces into the oscillatory circuit formed by the loop capacitor 4 and the loop winding 2 an equivalent resistance, the presence of which leads to damping of the oscillations in the loop; If the control object is removed from the core 9, then the resistance introduced into the circuit is minimal, the quality factor of the circuit is high and the resulting oscillations have a large amplitude.

Contactless switch operates as follows.

When the power supply bus 13 is turned on, the current is pulling through the channel

field-effect transistor 5, choke 6, feedback winding 3 and device output bus 14. Through the bipolar transistor 7, the current does not flow at this time, since its base-emitter junction is short-circuited by the coil 2 and the second choke 8, i.e. Bipole transistor 7 is closed. However, the current passing through the channel of the field-effect transistor 5, flowed through the winding 3, excites electromagnetic oscillations in a parallel contour, formed by the coytur winding 2 and the loop capacitor 4. The voltage oscillations enter the gate of the field-effect transistor 5, modulate the current flowing through it and, respectively, through the first choke b, which thus performs negative feedback on alternating current,. which increases the input resistance of the field-effect transistor 5 and reduces the resistance value introduced by the input circuit of the field-effect transistor to the oscillating contzF, i.e. does not reduce its quality factor. Bipol 5th transistor 7 is still closed and does not affect the conditions for the excitation of oscillations in the circuit. The gain of the field-effect transistor 5 is determined by the magnitude of the inductance of the first drossel 6 and pe depends on

the scatter of the values of the steepness of the input characteristics of the field-effect transistor

As the amplitude of oscillations in the circuit increases to a value that exceeds the voltage of the bipolar transistor 7 (i.e., about 0.5 V), when the half-wave of the oscillations opens, the base current of the transistor 7 occurs, which causes a bipolar collector current pulse transistor 7, which passes through the circuit: power supply bus 13, output 10 of auto-oscillator 1, collector-emitter junction of transistor 7, second choke 8, feedback winding 3, output 11 of auto-oscillator 1, device output bus 14. This current pulse in the feedback winding 3 pumps additional energy into the oscillating circuit, as a result of which the amplitude of the oscillations increases, and the current consumption of the device increases avalanche. Then, as a result of the negative feedback on the alternating current passing through the second choke 8, and the nonlinearity of the gain of the bipolar transistor 7 over the current is established by the stationary mode of self-oscillations corresponding to the on state of the switch, when through the output bus 14 flows a considerable current.

The amplitude of the stationary oscillations is determined by the magnitude of the input loss (insertion resistance) in the oscillatory circuit from the control object and the depth of the negative feedback and weakly depends on the current gain of the transistor 7, since the negative variable in the circuit of its emitter current, which increases the input impedance of the transistor 7, which does not reduce the quality factor of the oscillating circuit.

After the generator has reached the stationary mode of operation, the proximity switch is ready for operation and is in the on state (high output level).

When the control object is brought up to the end of the ferrite core 9, eddy currents are induced in the object, when the electrical field increases the resistance introduced into the oscillating circuit, decreases its Q-factor, which decreases

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em amplitude of electromagnetic waves.

. FIG. Figure 2 shows a view of the change in output signal when the gap between the end face of the core 9 and the control object is reduced. The inclusion of parallel-connected bipolar 7 and field 5 transistors into the active element of the autogenerator 1 makes it possible, using the nonlinearity of their total input characteristic, to obtain a hysteric character of the change in the output signal when the position of the control object changes. Thus, as the control object approaches the core 9, the insertion loss reaches such a value that the amplitude of oscillation decreases so much that self-excitation conditions are not fulfilled, and oscillations break down like an avalanche. The current in the output bus 14 decreases. The proximity switch is turned off. The conditions for the existence of 25 oscillations as the object approaches the core are determined only by the bipolar transistor 7 and the second choke 8.

After the oscillations of the oscillator 1 are oscillated, the bipolar transistor 7 closes and in the initial stage of oscillation when the control object is removed from the core 9 does not participate.

When the control object is removed from the core 9, the conditions for the occurrence of self-oscillations are again formed, and they do not depend on the conditions of the existence of self-oscillations when the control object approaches the core 9, and depend only on the steepness of the field-effect transistor 5 and the value of the inductance of the throttles 6. Difference in breakdown conditions and the occurrence of oscillations allows the formation of a hysteresis type of switching characteristic of a contactless switch. The position of the switch-on branch of the contactless switch is set by choosing the inductance of the first throttle 6, and the position of the switch-off branch by choosing the inductance of the second throw 8. At a further distance of the object from the core 9, the quality factor 5 of the circuit increases, the amplitude of oscillations in the circuit increases, the higher voltage of the unlocked bipolar transistor 7 turns on the second branch of the gene

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radios through the bipolar transistor 7. The oscillation amplitude increases sharply, after which, due to the nonlinearity of the input characteristic of the bipolar transistor 7, a transition occurs to the stationary mode of generation of electromagnetic oscillations. The proximity switch is turned on.

the power bus and the output switch capacitor of the filter and auto-oscillator of magnetoelectric oscillations, made according to the inductive three-point scheme, consisting of the active element, the magnetic system containing a ferrite core with nor therefore included windings

The stability of the position of the points of the contour and feedback links, and of the contact and disconnection of the contactless capacitor, and

the switch is provided by the presence of chokes 6 and 8 in the AC feedback circuits of transistors 5 and 7, respectively, and the position of each of the on / off characteristic branches can be

the element contains a field-effect transistor connected in series with the first inductor between the first output of the auto-oscillator of magnetoelectric oscillations connected to the switch power bus and the connection point of the windings of the magnetic system, the gate of the field-effect transistor is connected to the common point chosen independently by selecting the inductance value of the chokes 6 and 8, respectively. The range of the 20 contour winding and contour action of the contactless switch, the capacitor increases, and the free output of the winding, as it is determined by the condition of occurrence of a relatively small amplitude feedback oscillation, connected to the second output of the oscillator of the magnetoelectric oscillations, differing from ) created by the field trans-25 u and in order to expand the functionality, a bipolar transistor and a second daossel are added to the active element, and The bipol p-30 transistor lecturer is connected to the first output of the oscillator of magnetoelectric oscillations, the base is connected to the shutter of the pale-yellow transistor, and the emitter is connected via a second choke to the junction point of the magnetic system windings and the second

the bipolar transistor is turned on, which brings them up to the required power, sufficient for the subsequent switching of the contactless switch.

Claims (1)

Invention Formula Parallel connected between the element contains a field-effect transistor connected in series with the first inductor between the first output of the auto-oscillator of magnetoelectric oscillations connected to the switch power supply bus and the connection point of the windings of the magnetic system, the gate of the field-effect transistor is connected to the common point of the loop winding and the loop capacitor, and the free terminal of the winding which contour winding and contour capacitor, and the free output winding ki feedback. connected to the second output of the oscillator of magnetoelectric oscillations, which is different from the loop capacitor.