SU1229851A2 - Device for controlling electromagnets - Google Patents

Abstract

The invention relates to devices for driving electromagnets (EM) of the printhead when printing information and is additional to the author. St. No. 943905. The purpose of the invention is to reduce the level of radio interference. In the initial state at the inputs 12, the control signal is absent and no signals are received at the inputs of the transistors (T) 5. T 5 closed. The voltage at the input of the threshold organ (SW) 9 is close to "O" and from its output the enabling signal is fed to the second input of the coincidence circuit (CC) 2. When a signal appears at least at one of the inputs 12, it enters through the OR 10 element on the pulse shaper 11, which generates a signal that coincides with the control leading edge and overlaps it on the falling edge. From the output of the imaging unit 11, the signal arrives at the first input of the CC 2 and opens T 1. The control signal opens T 5, connecting the required winding EM 3 to the power source. The current through the windings EM 3 increases exponentially and when it reaches a predetermined value, the signal from the current sensors 7 through the element OR 8 goes to software 9, causing it to trigger. At the same time, a second signal is applied to the second input CC 2 and it closes T 1 by disconnecting the windings EM 3 from the power source. But the current in the EM due to the EMF of self-induction is preserved, the passage through the diode 4, the sensors 7 and the open T 5. When the current through the windings drops below a predetermined value, the software 9 returns to its original state and enables the CC 2 to work. present at the first input of the CC 2, T 1 opens again and the whole process repeats, maintaining the current setpoint in the windings while a signal is present in the control signal source. After the termination of the act of the governing sig- + g / i SL to to; o oo SP rsj

Description

T 5 closes. The signal from the driver 11 through the CC 2 leaves T 1 open. The self-induction current closes through the diodes 6 and the open T 1. When the signal from the driver T 1 ends, it closes. Self-induction current passes through diodes 4 and 6, and the energy stored in magnet1

The invention relates to telegraphy, in particular, to devices for driving the electromagnets of a print head during printing of information, and is an improvement of the known invention according to the author. St. No. 943905.

The purpose of the invention is to reduce the level of radio interference of the device.

FIG. 1 shows the basic electrical circuit of the proposed device; in fig. 2 - time diagrams of current pulses through an electromagnet.

The device contains a semiconductor switch made on transistor 1 and controlled by a matching circuit 2, which is connected between one of the terminals for connecting the power source and the leads of the electromagnets 3, which are connected via diode 4 with the other terminal for connecting the power source. Other findings of the electromagnets 3 are connected to other semiconductor switches made on transistors 5, and to other diodes 6.

Between the transistors 5 and the other terminal of the power supply, current sensors 7 are connected via the logic element OR 8 to the input of the threshold element 9. The first input of the circuit 2 coincides through another logical element OR 10 and the driver 11 of the pulses is connected to the inputs 12 of the device. The second input of the coincidence circuit 2 is connected to the output of the threshold organ.

The device works as follows.

In the initial state, in the absence of control signals at the inputs 12 of the device, the inputs of the OR 10 circuit and the inputs of the transistors 5 do not receive signals and the transistors 5 are closed. The current through the current sensors 7 is missing. The voltage at the input of the threshold organ 9 is close to zero, and from its output, the permitting signal is fed to the second input of the circuit 2 of coincidence. When at least one of the inputs 12 of the device appears, the signal goes through the element OR 10 to the pulse shaper 11, which generates a signal that coincides with the control leading edge and overlaps it along the back EM field. A decrease in the level of radio interference is achieved by the fact that when the EM is switched off at the initial moment, the duration of the trailing edge of the current pulse increases and the rate of change of the magnetic field decreases, which determines the level of radio interference. 2 Il.

th front. From the output of the driver 11, the generated signal arrives at the first input of the circuit 2, opening the transistor 1. The control signal opens the transistor 5, connecting the required coil of electromagnets 3 to the power supply.

The current through the windings of the electromagnets 3 increases exponentially and when it reaches a predetermined value, the signal from the current sensors 7 through the OR circuit 8 to the threshold organ 9 causes it to trigger. In this case, a prohibiting signal is supplied to the second input of the coincidence circuit 2 and it closes the transistor 1, thereby disconnecting the windings of the electromagnets 3 from the power source, however, the current in the electromagnets due to the self-induced EMF is maintained, the passage through the diode 4, the sensors 7 and the open transistors 5.

When the current through the windings falls below a predetermined value (determined by the threshold organ defined by the width of the hysteresis loop), it returns to the initial state and enables the coincidence circuit 2 to operate. Since the generated signal is present at the first input of the matching circuit 2, the transistor 1 opens again and the specified process is repeated, maintaining the current setpoint in the windings while the signal is present in the control signal source.

After the termination of the control signal, the transistors 5 are closed. The signal from the driver 11 through the coincidence circuit 2 leaves the transistor 1 open. The self-induction current is closed through the diodes 6 and the open transistor 1 (Fig. 2). At the end of the signal from the driver, the transistor 1 is closed. In this case, the self-induction current passes through diodes 4 and 6 and the energy remaining from the electromagnet stored in the magnetic field is given to the power supply.

A decrease in the level of radio interference is achieved by the fact that when the electromagnet is turned off at the initial moment, the duration of the trailing edge of the current pulse increases and, consequently, the rate of change decreases.

magnetic field determining the level of radio interference.

Claims (1)

The invention The device for controlling electromagnets according to ed. St. No. 943905, different In order to reduce radio interference, a pulse driver is inputted into it, the input of which is connected to the output of another OR element, and the output is connected to the first input of the matching element. tynp but FIG. 2 Editor A. Kozoriz Order 2231/53 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab. 4/5 Branch PPP "Patent, Uzhgorod, st. Project, 4 Compiled by A. Karetnikov Tehred I. Veres Corrector L. Patay Circulation 643 Subscription