KR200249320Y1 - Apparatus for transforming rotation numbers of motor into voltage - Google Patents

Abstract

The present invention relates to a rotation speed voltage conversion device of a motor for detecting the speed of the motor used in the crane and converting the voltage. A rotary encoder for detecting the rotation of the motor so that the motor can be controlled by converting the rotational speed of the motor into a voltage, an LCD display for calculating and displaying the motor speed from the input from the rotary encoder, and the motor rotation speed The invention includes a speed measuring unit for converting the voltage into a corresponding voltage, and a direction determining circuit for determining a rotation direction of the motor. Accordingly, while satisfying the specifications of the conventional taco generator, the main controller of the crane is supplied with a signal indicating the dangerous state and a signal indicating the direction of rotation of the motor when the motor falls below or exceeds the reference speed. More secure and accurate motor control can be achieved than using.

Description

Rotational voltage converter of motor {APPARATUS FOR TRANSFORMING ROTATION NUMBERS OF MOTOR INTO VOLTAGE}

The present invention relates to a rotational voltage conversion device for a motor including a function of detecting a speed of a motor used in a crane and the like and converting the voltage into a voltage and generating a dangerous signal when the reference speed is below or exceeded.

Cranes are generally used to move heavy loads such as steel and containers up, down, left and right using motors. If the motor breaks down or malfunctions while moving heavy objects, not only property damage but also human damage can occur. In order to prevent a malfunction due to the overload of the motor, the power is transmitted through a current transducer (CT) to stop the operation of the motor in the current controller when a current of more than a predetermined value flows. Therefore, in order to determine whether the rotation speed of the motor is higher or lower than the reference, a taco generator (TG) is installed on the shaft of the motor and has a double protection device for detecting an error in the rotation speed. In particular, accurate measurement of the number of revolutions of the motor is important because it can prevent safety accidents and reduce the probability of failure. Since most of the analog control cranes that are in use today are manufactured long ago and controlled mechanically, the precision is inferior, and failure due to wear occurs frequently near the contact point of the taco generator.

1 shows a motor control unit of a conventional crane. In the motor used in the crane, as shown in FIG. 1, the tacho generator TG generates an induced electromotive force according to the rotational speed of the motor and returns it to the speed controller 10. In general, the crane drives the motor M using a voltage of 440 V / 60 Hz, and supplies 220 V / 60 Hz of the reduced pressure to the motor control unit of the crane. When the speed of the motor M does not match the reference speed, the speed controller 10 operates to stop the operation of the motor M. FIG. That is, in the conventional crane, the induced electromotive force is generated and sent to the speed controller 10 according to the rotation speed of the motor M using the taco generator TG, and the speed controller 10 determines the induced electromotive force. The motor M rotation speed is compared with the reference speed to determine whether the current speed is normal, and if abnormal, the operation of the motor M is stopped.

However, in such a conventional apparatus, since the taco generator TG is in direct contact with the motor shaft, the wear and tear occurs naturally when used for a long time, and since the taco generator TG rotates, a failure occurs and is maintained earlier than the life cycle of the taco generator TG. There is a problem of increasing the expense of remuneration. In addition, even if the current motor speed is greater than the reference speed and the threshold value does not have a control function to stop the motor immediately, the occurrence rate of the accident is high. In addition, there is a risk of an accident if the direction of rotation signal is incorrectly connected when replacing the device. Therefore, it is possible to secure the trust of the installer by solving problems such as the taco generator coupling (coupling) which is a mechanical device, the problem of facility safety accident when overspeed occurs, and the taco generator when the coupling is damaged. Therefore, there is a need for the development of a motor speed measuring device, a frequency-voltage converter, and a device for controlling and transmitting the motor to prevent an accident and equipment delay.

The present invention is designed to solve such a problem, and serves the same role as a conventional taco generator, generates a danger signal when the motor exceeds the maximum speed and falls below the minimum speed, and can quickly determine the direction of rotation of the motor. It is to provide a rotational voltage conversion device of a motor having a function.

1 is a block diagram showing a motor control unit of a conventional crane

2 is a graph showing output voltage versus time output from a conventional taco generator

3 is a graph showing the RPM change of the taco generator against voltage

Figure 4 is a block diagram showing a rotation speed voltage conversion device of the present invention

5a is a structural diagram of a disk of the rotary encoder of FIG.

5B is an output waveform diagram of the rotary encoder of FIG. 4.

6 is a block diagram of a speed measuring unit of FIG. 4.

FIG. 7A is a circuit diagram of the level shifter of FIG. 6

7B is a graph of simulation results of the level shifter of FIG. 6.

8A is a circuit diagram of the direction plate of FIG. 4.

FIG. 8B is a graph of simulation results in the clockwise direction in FIG. 10A

8C is a graph of simulation results in the counterclockwise direction in FIG. 10A.

9 is a flowchart for explaining an output algorithm of a drctn signal.

10 is a flowchart illustrating a rotation speed voltage conversion process of a motor;

* Description of the symbols for the main parts of the drawings *

1: motor 2: rotary encoder

3: LCD display part 4: Speed measuring part

5: direction determiner 10: speed controller

15 current controller 20 gate driving circuit

25: SCR Bank 30: External Register

35: Microprocessor B 40, 55: D / A Converter

45, 60: level shifter 50: microprocessor C

65: flip-flop M: motor

CT: Current Converter OP1: First Operational Amplifier

OP2: second operational amplifier OP3: third operational amplifier

In order to achieve the above object, the rotation speed voltage conversion device of the motor of the present invention, coupled to the shaft of the motor encoder for detecting the rotation of the motor, and calculates the motor speed from the input from the rotary encoder And an LCD display unit for displaying, a speed measuring unit for converting the motor rotational speed into a voltage, and a direction determining unit for determining the rotational direction of the motor.

According to the present invention of the above configuration, while satisfying the specifications of the conventional taco generator, the signal indicating the dangerous state when the motor falls below or exceeds the reference speed to the main control portion of the crane and the signal indicating the direction of rotation of the motor Can be supplied to perform safer and more accurate motor control than using a taco generator.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

There are many types of taco generators used in the crane, but in the embodiment of the present invention will be described taking the case of the same as the specification of the taco generator (TG) having a maximum speed of 1000 RPM.

The taco generator TG generates a voltage corresponding to the motor speed by the same principle as the generator, and generates a negative voltage or a positive voltage according to the rotation direction.

Fig. 2 is a graph showing the output voltage versus time output from a conventional taco generator, which takes the gear of the crane from neutral to four stages and then stops at the fourth stage with the output voltage of the taco generator TG over time. It is time. It can be seen that the time taken for the output voltage of the taco generator to reach 0V to 10V takes about 7 seconds and increases linearly. In addition, the time taken by the taco generator TG to stop in the fourth gear takes about 5 seconds. The maximum change rate of the voltage change with respect to the time of the taco generator TG is obtained from Equation 1 below.

ΔV / Δt = 10/5 = 2 (V / S)

Therefore, the slew rate of the frequency-to-voltage converter must be operated at 2 (V / S) or more.

3 is a graph showing the RPM change of the taco generator with respect to the voltage, it can be seen that the output voltage increases linearly with RPM. The rate of change ΔRPM / ΔV of the RPM with respect to voltage is expressed by Equation 2.

(1038/10) (RPM / V) = 103.8 (RPM / V) = 10.38 (RPM / 0.1V)

Thus, the frequency-to-voltage converter must have a rate of change of at least 0.1V for 10.38 RPM. And since the taco generator (TG) operates like a generator, the converter must generate a positive voltage or a negative voltage according to the direction of rotation.

Figure 4 is a block diagram showing a rotational voltage conversion device of the present invention.

Referring to Figure 4, the present invention is a device for converting the number of revolutions of the motor to a voltage output. The rotation speed voltage converter of the motor 1 includes a rotary encoder unit 2 for measuring the rotation of the motor using an optical sensor, and a speed measuring unit 4 for calculating the rotation speed of the motor 1 using a microprocessor. And an LCD display unit 3 for displaying, for example, the current rotational speed of the motor 1 on the LCD, and a direction determiner 5 for determining the direction of the motor 1.

The microprocessor requires ± 12V power supply because the + 5V power supply and the output have a value between -10V and + 10V. Therefore, the microprocessor uses an SMPS power supply with a built-in protection circuit. When the rotation of the motor 1 is given to the input of the rotary encoder 2, a pulse waveform according to the rotation is generated at the output of the rotary encoder 2. The speed measuring unit 4 generates an output voltage between -10V and + 10V depending on the rotational speed of the motor 1 at its OUTPUT terminal, and EM indicates that the rotational speed of the motor 1 is out of the minimum and maximum speeds. It is a signal that it is dangerous, and OS and LS are signals that go high when the maximum and minimum speeds are exceeded. In addition, the drctn outputted from the direction determiner 5 outputs values of -10V, + 10V, and 0V depending on the rotational direction of the motor, and RR and LR indicate that the motor rotates clockwise and counterclockwise, respectively. . The output signals of OUTPUT, EM and drctn are sent to the speed controller 10 shown in FIG. 1 for use in controlling the motor. The OS, LS, RR and LR signals indicate the state of the motor in the transducer. G is an input terminal for telling the gear stage of the motor 1 in the speed controller 10.

Referring to the rotary encoder in Figure 2 with reference to Figures 5a, 5b in detail as follows.

5A is a structural diagram of a disk of the rotary encoder of FIG. 4.

5B is an output waveform diagram of the rotary encoder of FIG. 4.

The rotary encoder portion 2 is connected to the motor shaft by using a coupling, and the disc is formed with three rows of grooves, for example, as shown in Fig. 5A. In the Z column, one groove for synchronization is formed, and in the A and B columns, 60 grooves are formed to overlap each other. A light emitting diode (not shown) is installed on one side of the disc, and a photo sensor (not shown) is installed on the opposite side of the disc so that light passing through the grooves is rotated by the photosensor as the disc rotates clockwise. It is detected and generates a square wave as shown in FIG. 5B. For example, if 60 grooves are provided in each of columns A and B, 60 square waves are generated every time the motor rotates, and thus, one square wave is generated every 6 degrees of rotation of the motor. The number of grooves is not limited to this, but can be increased or decreased as needed, and the rotation direction is possible in both clockwise and counterclockwise directions.

Referring to Figure 6 with respect to the speed measuring unit in Figure 4 as follows.

6 is a block diagram of the speed measuring unit of FIG. 4.

6 briefly illustrates the speed measurement unit 4. The speed measuring unit 4 includes an 8-bit microprocessor B (named: PIC16F84B) 35 having a control function, a D / A converter 40 for converting a digital signal into an analog signal, and a D / A converter 40. And a level shifter 45 for converting the output of the controller to match the input of the main controller. In FIG. 6, A is a signal output from the rotary encoder unit 2, and D is a motor rotation direction signal output from the direction determining unit 5.

When the motor 1 rotates, the rotary encoder 2 generates a pulse wave A, and this signal A is input to the TMR0 terminal, which is the 0 th timer of the microprocessor B 35. In the embodiment of the present invention, the maximum rotational speed of the motor is about 1000 RPM, and the motor rotational speed at each stage of the gear is shown in Table 1 below.

1 stage 2-stage 3-stage 4-stage RPM of motor 250 500 750 1000 RPM of rotary encoder 15000 30000 45000 60000 0.1 sec 25 50 75 100 ± 10% 22-28 45-55 78-82 90-100

In Table 1, since the rotation speed is the number of revolutions in one minute, not only the real-time rotation number is known but also the exact value cannot be obtained. Therefore, the output of the rotary encoder section 2, which divides one rotation of the motor 60, is used as the input of TMR0. do. And the number of pulses of the rotary encoder part 2 which generate | occur | produced in 0.1 second is calculated. If the gear is out of the range of 10% from the standard pulse number, the LED will emit light and the buzzer will sound to inform the user. Will stop the operation.

In order to control the rotation speed of the motor calculated for 0.1 second in the microprocessor B 35 in comparison with the reference speed, the digital signal must be converted into an analog signal, and in this process, the D / A converter ( 40) is used. Since parallel communication requires many pins, an 8-bit serial input D / A converter [name: MAX522 [6]] (40) is used to reduce the number of pins. The D / A converter 40 communicates with the microprocessor B 35 using chip selection, data input and clock. The microprocessor B 35 first sends a control command to the D / A converter 40 and then sends code data. Table 2 below shows the relationship between the number of revolutions of the motor and the output voltage of the D / A converter 40.

Pulse number (0.1 second) D / A Converter Input Code (Hexadecimal) D / A converter output voltage (V) +100 e0 4.5 +75 c7 4.0 +50 ae 3.5 +25 96 3.0 0 80 2.5 -25 67 2.0 -50 4e 1.5 -75 35 1.0 -100 1c 0.5

When the motor rotates in the forward direction, the output is between 3.0V and 4.5V. When the motor rotates in the reverse direction, it outputs a value between 0.5V and 2.0V.

The level shifter will be described in detail with reference to FIGS. 7A and 7B as follows.

The taco generator (TG) voltage has a value between -10V and + 10V. However, since the output of the D / A converter 40 has a value between 0.5V and 4.5V, it is necessary to perform a level shift to match the output voltage of the taco generator TG.

FIG. 7A is a circuit diagram of the level shifter of FIG. 6.

Referring to FIG. 7A, the first operational amplifier OP1 is for generating -2.5 V. The LM336 [7] is used to generate a reference voltage of 2.5 V to the negative input of the first operational amplifier OP1. To generate -2.5V. This voltage is added to the output voltage of the D / A converter 40 and supplied to the input terminal of the second operational amplifier OP2 of the next stage serving as an adder. The output voltage of the second operational amplifier OP2 is obtained as follows.

_{V A = -R 19 / R 18} · V ref

V _B = -R ₂₀ / R ₁₅ · (V _A + V _i )

_{V out = -R 17 / R 16} · V B

If R ₁₈ = R ₁₉ and R ₁₆ = R ₁₇ ,

V _out = -R ₂₀ / R ₁₅ (-V _ref + V _i )

By adjusting the size of R ₂₀ in Equation 6, the output voltage may have a value between -10V and + 10V.

Since the output of the D / A converter 40 is inverted and appears at the output terminal of the second operational amplifier OP2, the third operational amplifier OP3 serves as an inverter for inverting the input. Each of the operational amplifiers OP1, OP2, and OP3 uses LM741.

The operation of the level shifter 45 described above using the Pspice program will be described with reference to FIG. 7B.

7B is a graph of a simulation result of the level shifter of FIG. 6.

As can be seen from the graph, it can be seen that the input voltage V _in output from the D / A converter 40 and input to the level shifter 45 increases linearly from 0 to 4.5 V. The output voltage V _out of the level shifter 45 has a value of -10 to +10 V while the operational amplifiers OP1, OP2 and OP3 of the level shifter 45 have a value of -10 to +10 V. You can see that it performs well.

In addition, in FIG. 4, the LCD display unit 3 displays the RPM obtained by measuring the time between pulses output from the rotary encoder 2 and calculating the frequency so as to display the rotation speed of the motor.

Referring to FIGS. 8A, 8B, and 8C, the direction decision unit in FIG. 4 is as follows.

The direction of the motor can be determined using the output of the rotary encoder 2. That is, since two square waves having some parallax are generated from the grooves of the two rows of the disc of the rotary encoder 2, it can be discriminated by using them.

8A is a circuit diagram of the direction determiner of FIG. 4.

As can be seen from FIG. 8A, the direction determiner 5 converts the digital signal output from the microprocessor C 50 and the microprocessor C 50 into a analog signal to control the direction of the motor. D / A converter 55 for outputting a predetermined voltage and a level shifter for generating a drctn signal by shifting the voltage output from the D / A converter 55 to a voltage necessary for the operation of the direction determiner 5. 60 and a deflip-flop 65 for outputting a value corresponding to the rotational direction in accordance with the signal value output from the rotary encoder 2.

Simulation of the operation of the direction determiner 5 having the above configuration using the MAX + PLUS II simulator will be described with reference to FIGS. 8B and 8C.

FIG. 8B is a graph of simulation results in a clockwise direction in FIG. 8A.

FIG. 8C is a graph of the simulation result in the counterclockwise direction in FIG. 8A.

8B and 8C, A and B show two output waveforms of the rotary encoder unit 2. FIG. The R signal indicates the driving state of the motor. The microprocessor C 50 outputs 1 when the motor is moving and 0 when the motor is stopped. The D signal is clockwise according to the signal value input from the rotary encoder 2. In case 1, counterclockwise, 0 value is output and when the motor is not driven, that is, when R value is 0, the drctn voltage is output as 0 V unconditionally and does not affect drctn voltage regardless of 0 or 1 The x value is printed. The RR signal and the LR signal are values determined according to the output value of the flip-flop 65, which indicates whether the rotation of the motor is currently clockwise or counterclockwise. In the clockwise direction, the RR signal is 1; in the counterclockwise direction, the LR signal is 1. Otherwise, all zero values are output.

The microprocessor C 50 outputs a predetermined hexadecimal code value to the D / A converter 55 according to the rotation direction. The code value has a value between 0x00 and 0xFF. When the motor rotates to the right, it outputs 0x80 ~ 0xFF and when it rotates to the left, it outputs 0x00 ~ 0x80.

For example, in the clockwise direction as shown in FIG. 8B, the output of the deflip-flop 65 becomes high (1) at the rising edge of the B input and the RR signal becomes high (1). Table 3 below shows the state of the direction determiner 5 according to the input.

R D RR LR drctn 0 x 0 0 0 V stop One One One 0 + 10V Clockwise One 0 0 One -10V Counterclockwise

As can be seen from Table 3, R signal is 0 because it does not operate at stop, D signal is x value which does not affect drctn voltage value at 1 or 0 value, and drctn voltage because R signal is 0. The value is 0 V, and RR and LR are 0.

Since it operates in the clockwise direction, the R signal is 1, the D signal is 1, and because the clockwise direction, the RR value is 1 and the drctn voltage value is + 10V.

Since it operates in the counterclockwise direction, the R signal is 1, the D signal is 0, and since the counterclockwise direction, the LR value is 1 and the drctn voltage value is -10V.

From this, the speed controller 10 requires a voltage of + 10V in the clockwise direction, -10V in the counterclockwise direction, and 0V in the non-operational manner so that the speed can be controlled using the rotational direction of the motor. .

The process of determining the direction by the direction determiner 5 will be described with reference to the flowchart of FIG. 11 as follows.

11 is a flowchart illustrating an output algorithm of a drctn signal.

Referring to Fig. 11, the direction determining unit 5 is initialized as a whole (P100).

The microprocessor C 50 initializes the driving state R of the direction determiner 5 (P200).

The P200 is a process of outputting an R signal value of 0 as a display of a state of not currently rotating.

The microprocessor C 50 outputs the driving stop code 0x80 to the D / A converter 55 (P300).

The TMR0, which is the 0 th timer of the microprocessor C 50, counts the output of the rotary encoder 2 (P400).

The microprocessor C 50 determines whether the value counted by the timer is 0 (P500).

If the value counted by the timer in step P500 is 0, the microprocessor C 50 outputs a signal indicating that the current driving state R is stopped through the R port (P600).

The R signal value output in step P600 is zero.

The microprocessor C 50 outputs 0x80, which is a code indicating a driving stop state, to the D / A converter 55 (P700).

If the value counted by the timer in step P500 is not 0, the microprocessor C 50 outputs a signal indicating that the current driving state R is being driven through the R port (P800).

The R signal value output in step P800 is 1.

The microprocessor C 50 determines the output signal of the flip-flop 65 to determine whether the rotation direction of the currently driven state is a counterclockwise direction (P900).

In step P900, if the signal D output from the flip-flop 65 is 1, it is clockwise, and if it is 0, it is counterclockwise.

In the counterclockwise direction in P900, the microprocessor C 50 outputs 0x00, which is a code indicating rotation in the counterclockwise direction, to the D / A converter 55 (P1000).

In the clockwise direction in P1000, the microprocessor C 50 outputs 0xFF, which is a code indicating to rotate clockwise, to the D / A converter 55 (P1100).

In the above processes P1000, P1100, and P1200, the value output to the D / A converter 55 is 0V when the voltage level is shifted by the level shifter 60 and is in the stop state, + 10V in the clockwise direction, and counterclockwise. A -10V is output as a drctn voltage (P1200), and the process is repeated from the process P500.

Hereinafter, the rotation speed voltage conversion process of the motor in the present invention will be described with reference to the flowchart of FIG. 10 based on all the above contents.

10 is a flowchart illustrating a rotation speed voltage conversion process of the motor.

Referring to FIG. 10, the rotation speed voltage conversion device of the motor is initialized as a whole so as to generate a danger warning signal (S100).

The microprocessor B 35 of the speed measuring unit 4 reads the rotation direction and the gear stage based on the direction signal D and the gear stage signal G of the direction determiner 5 (S200).

The microprocessor B 35 initializes TMR0, which is the 0th timer (S300).

The microprocessor B 35 delays all operations by a time of 0.1 seconds to calculate the rotation speed of the motor (S400).

The timer counts the number of revolutions for a time of 0.1 seconds (S500).

The microprocessor B 35 determines whether the counted rotation speed is within a reference range corresponding to each gear stage (S600).

If the number of revolutions counted in step S600 exceeds the reference range, the microprocessor B 35 generates a danger warning signal EM (S700).

The microprocessor B 35 generates the danger warning signal EM and initializes the D / A converter 40 at step S800.

The microprocessor B 35 initializes the D / A converter 40 and turns on the LED and the buzzer at step S900.

The microprocessor B 35 delays all operations to ring the LED and the buzzer for about 3 seconds (S1000), turns off the LED and the buzzer (S1100), and moves to the process S1700 described later.

If the rotation speed counted in step S600 is within the reference range, the danger warning signal EM is not generated (S1200).

The microprocessor B 35 receives the direction signal D input from the direction determiner 5 and determines the current rotation direction (S1300).

If the rotation direction is counterclockwise in step S1300, the microprocessor B 35 calls a code value between negative tables 0x00 to 0x80 (S1400).

If the rotation direction is clockwise in step S1300, the microprocessor B 35 calls a code value between the positive tables 0x80 to 0xFF (S1500).

When the negative table and the positive table are called, the microprocessor B 35 outputs the code value of each table to the D / A converter 40 (S1600).

The microprocessor B 35 repeats all operations of the speed measuring unit 4 by 0.1 second (S1700) and then repeats the process from step S200.

Through all the above processes, the rotation speed voltage conversion device of the motor is implemented as intended by the present invention.

As described above, according to the present invention, not only can the motor speed of the crane be controlled electronically but also mechanically, thereby extending the life of the rotational speed voltage converting device of the motor, and when the motor speed is out of the normal value, It has the effect of stopping the generation and the operation of the motor quickly and accurately.

Claims (5)

In the apparatus for controlling the motor in accordance with the rotational speed of the motor, comprising a speed controller for controlling the rotational speed of the motor, A rotary encoder unit coupled to the rotating shaft of the motor to detect rotation of the motor; A speed measuring unit for converting the number of revolutions measured by the rotary encoder into voltage, And a direction determiner for determining a rotation direction according to the output of the rotary encoder and outputting a predetermined voltage according to the direction. The method of claim 1, wherein the rotary encoder unit, A first row Z in which one groove is formed for synchronization; A second row A in which a plurality of grooves are formed at equal intervals, And a disc having a third row B formed to overlap with the grooves of the second row at equal intervals, the same number of grooves being formed in the second row, The rotation speed voltage conversion device of the motor is provided with a light emitting diode and a photo sensor on each side of both sides of the disc. The method of claim 1, wherein the speed measuring unit, A microprocessor B (35) for processing a signal output from the rotary encoder (2), outputting it as a digital signal, and controlling the signal; A D / A converter 40 for converting a digital signal output from the microprocessor B 35 into an analog signal, And a level shifter (45) for converting the output of the D / A converter (40) to match the input of the main control plate. The method of claim 1, wherein the direction determining unit, A microprocessor C (50) having a control function for determining the direction of the motor; A D / A converter 55 for converting a digital signal output from the microprocessor C 50 into an analog signal and outputting a predetermined voltage; A level shifter 60 for generating a drctn signal by shifting the voltage output from the D / A converter 55 to a voltage necessary for operating the direction determiner 5; A rotation speed voltage conversion device for a motor, including a deflip-flop (65) for outputting a predetermined value according to the rotation direction in accordance with a signal value output from the rotary encoder (2). The method of claim 3 or 4, wherein the level shifter, A first operational amplifier OP1 for generating a reference voltage by applying a reference voltage to a negative input of the first operational amplifier OP1; A second operational amplifier OP2, which is combined with a predetermined voltage output from the first associating amplifier OP1 and the output voltage of the D / A converter, is input, serves as an adder, and outputs a voltage value within a predetermined range; A rotational voltage conversion device for a motor including a third operational amplifier (OP3) to invert the input of the second operational amplifier (OP2) to serve as an inverter.