SU1274145A1 - Contactless switch - Google Patents

Abstract

The invention relates to the field of control and automatic control and can be used in electronic systems for tracking the position of an object. The purpose of the invention is to increase the reliability of the device by increasing the stability of its operation with changes in the supply voltage and temperature by providing a hysteresis switching characteristic and stabilizing the position of the displacement points and the output current levels. For this, the device has introduced a deep current feedback circuit for the throttle, and a field-effect transistor is used as the active element of the oscillator. The device contains magnetoelectric oscillation oscillator 1, loop winding 2, feedback winding 3, circuit capacitor 4, field-effect transistor 5, choke 6, ferrite SS core 7, power supply terminals 11 and 9, output bus 12, 2 silt

Description

f The invention relates to control (5th and automatic control and can be used in electronic systems for tracking the position of the object. The aim of the invention is to increase the reliability of the device by increasing the stability of its operation when the supply voltage and temperature are varied by providing a hysteresis switching characteristic and stabilization of switching points and levels of output current signals by using a field-effect transistor as an active element and introducing Fig. 1 is a schematic diagram of the device; Fig. 2 is a view of the switching characteristic of a contactless switch. The device contains an auto-oscillator 1 of magnetoelectric oscillations, consisting of series-connected loop winding 2 and a winding 3 of the reverse connection, loop capacitor 4, field transistor 5, droplets 6, ferrite core 7, Conclusions 8 and 9 of the oscillator 1 are connected to the plates of the filter capacitor 10 and, respectively, to the bus 11 source The power supply and the output bus 12, the self-oscillator 1 is made according to the inductive three-point scheme using the field-effect transistor 5 as the active element, the source of which is connected to the common connection point of the windings 2 and 3 to the common connection point the connection point of the loop coil 2 and the contour capacitor 4, and the drain to one of the pins 8 of the autogenerator 1 and to the supply bus 11, the second output of the loop capacitor 4 and the second output of the feedback winding 3 are connected to the second pin 9 of the autogenerator I output bus 12 by turning off the tel. FIG. Figure 2 shows the dependence of the current of the output bus 12 as a function of the position (gap, mm) of the ferrite core. The control object is located at some distance from the core core 7 and, depending on this distance, introduces into the oscillatory circuit formed by loop capacitor 4 and windings 2 and 3 an equivalent resistance, which leads to attenuation of electromagnetic oscillations in the circuit. If the control object is removed from the core 7, 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. The device works as follows. When the power supply bus 1i is turned on, the current flows through the channel of the transistor 5, the inductor 6, the feedback winding 3 to the output bus 12 of the device. This current, flowing through the winding 3, excites electromagnetic oscillations in a parallel circuit formed by windings 2 and 3 and capacitor 4. performs deep negative feedback on alternating current, which pushes the input resistance of the transistor 5 and reduces the resistance value introduced by the input circuit of the field-effect transistor into an oscillating circuit, t, e, uv its good quality is precious. The gain of transistor 5 is determined by the magnitude of the inductance of droplets 6 and does not depend on the spread of the steepness values of the input characteristic of the field-effect transistor 5. in the circuit, and then at high gate currents - decrease. The stationary state of the oscillator in the presence of oscillations in the circuit corresponds to the on state of the switch, when a considerable current flows through the output bus 12. The amplitude of oscillations is determined by the amount of insertion loss (insertion resistance) into the oscillatory circuit from the object of control. After the generator has reached the stationary mode of operation, the proximity switch is ready for operation and is at its disposal.

3

It is in the on state (high output),

When the control object is brought to the end, the ferrite core 7 in the object is induced by eddy currents, the resistance introduced into the oscillating circuit increases, its Q-factor decreases, which reduces the amplitude of the electromagnetic oscillations.

Fig. 2 shows the output change when the gap between the end face of the core 7 and the test object is reduced. Switching on the field-effect transistor with zero voltage offset allows using the nonlinearity of the input characteristic of the field-effect transistor 5 to obtain a hysteresis change in the output signal when the position of the control object changes. Thus, as the control object approaches the core 7, the insertion loss reaches such a value that the amplitude of the oscillations decreases so much that the transistor leaves the forward gate current mode, and the oscillations stop, In the off state of the device, the current is h Through the transistor and, therefore, the output current is small.

When the object is removed from the core 7, the conditions for self-oscillation again form. However, their occurrence does not begin at the point of their disappearance when the object is introduced, but somewhat further. This is due to the low gain value of the transistor 5, which at this moment is not in the forward gate current mode. The difference in the conditions of breakdown and the occurrence of oscillations in the circuit allows the formation of a hysteresis type of switching characteristic of the device. Further removal of the object from the core I increases the quality factor of the oscillating circuit. The energy supplied by the transistor 5 to the winding 3 becomes sufficient.

Accurately for sustaining undamped oscillations. The amplitude of the continuous oscillations begins to grow like an avalanche, as the transistor switches to the forward gate current mode, and the device turns on.

The stability of the device on and off points when the power supply voltage and temperature fluctuate is ensured by the presence of throttles in the source circuit of the field-effect transistor, which creates deep negative current feedback.

The reliability of operation and unambiguity in determining the position of an object in the zones of a differential travel is also ensured due to the hysteresis nature of the switching, which allows the device to be used in conditions of mechanical vibrations and accelerations.

Claims (1)

Invention Formula A contactless switch, containing a parallel-connected filter capacitor and an oscillator of magnetoelectric oscillations, made according to the inductive track circuit, consisting of an active element, a magnetic system containing a ferrite core with series-connected loop and feedback windings, and a loop capacitor connected between free turning, Am windings, characterized in that, in order to increase reliability, a choke is inserted into it, and the active element is designed as a field effect transistor A, the source of which is through a specified choke is connected to the connection point of the windings of the magnetic system, the gate is connected to the common output of the loop winding and the loop capacitor, and the drain is one of the leads of the magnetoelectric oscillation oscillator. FIG. 2