JPS59216317A - Monostable multivibrator - Google Patents

Abstract

PURPOSE:To vary easily the time constant of a monostable multivibrator by using an integrating circuit consisting of an operational amplifier and a level comparator and comparing the integral voltage having a linear gradient with a prescribed reference voltage. CONSTITUTION:Since an output voltage E0 of an operational amplifier 210 rises with a certain gradient until an FET 214 is turned on, this voltage E0 becomes a level proportional to the length of the period of an input pulse Pf. When E0>thetaV is true between the voltage E0 and a reference voltage thetaV, an output MQ of an operational amplifier 220 becomes low-level. Consequently, since the time constant of a monostable multivibrator 20 is determined by the gradient of the output voltage E0 of an integrating circuit 21 and the comparison reference voltage thetaV of a comparing circuit 22, the period of the monostable multivibrator 20 is changed when a variable resistance 221 is varied.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a monostable multivibrator of the Ridriger type.

Background Art and Problems For example, when a chain breaks on a belt conveyor, the load on the motor driving the belt conveyor is lost, causing the motor to run out of control, resulting in a dangerous situation. Therefore, by detecting the moving speed of the belt conveyor,
When this stops, it is necessary to stop the motor.

Furthermore, when manufacturing adhesives, the agitation must be stopped when the adhesive has been agitated to a suitable viscosity. To do this, for example, the rotational speed of the stirring rod is adjusted, and when the rotational speed becomes less than a predetermined value, the stirring is stopped based on the detection output.

A speed detection circuit as shown in FIG. 1 has been proposed as a suitable speed detection circuit for detecting such a stop.

That is, in FIG. 1, (11 is, for example, the input terminal of the pulse Pf (FIG. 2A) whose frequency is proportional to the rotational speed,
This pulse Pf is supplied to a ridrigger type monostable multi-bi break (2), and this monostable multi-bi break (2) is triggered by the falling edge of the pulse Pf.

The time constant τi of this monostable multi-bibreak (2) is selected to be approximately equal to the period of the pulse Pf at the rotational speed to be detected. Therefore, while the period of the input pulse Pf is smaller than τi, that is, when the rotation speed is lower than the speed to be detected, this monostable multi-by-break (
The output MQ (FIG. 2B) of 2) is always at a high level. Then, when the rotational speed becomes lower than the speed to be detected and the period of the human power pulse Pf becomes larger than τ, the output MGL of the monostable multivibrator (2) becomes the second
Inverts to low level as shown in the figure.

The output MGL of this monostable multi-bi break (2) is D
It is supplied to the D terminal of the flip-flop circuit (3).

-Everyone's Capulse Pf is this D flip-flop 1 circuit + 3
1 (7) This pulse Pf is supplied to the clock terminal.
At the rising edge of , the output M of the monostable multi-bi break (2) is sampled, and its value, that is, high level or low level, is the output of this 079717071 circuit (3).
is memorized. Therefore, the output from this 079717071 circuit (3) rises at a time delayed by l pulses of pulse Pf from the rise of output M of monostable multi-bi break (2), and when the period of pulse Pf becomes larger than τi, A signal FQ (FIG. 2C) is obtained which rises at the instant of the immediately following pulse.

How to output the monostable multi-bi break (2) MQ and the output F1 of the flip-flop circuit (3); L is the AND circuit (4
), from which an AND output Ao (FIG. 2D) is obtained which is at a high level from the time when the output F rises to the time when the output Mα falls.

This output A is at a high level when the rotational speed is above a certain speed, and falls to a low level when the rotational speed is lower than that speed. In other words, this cutting edge is a detection signal indicating whether the rotational speed is below a predetermined speed.

Therefore, it is possible to stop the rotation, for example, by the fall of this detection signal.

As described above, this speed detection circuit can detect that the speed has fallen below a predetermined value with an extremely simple configuration. For example, when the present invention is used for stoppage detection, it is possible to obtain a detection output that substantially coincides with the stoppage timing of the subject. Often, after detecting a stop, the last pulse (
Even if the pulse PN shown in FIG. 2 occurs, there will be no false detection that the speed has increased again due to this pulse PN.

Of course, this circuit can also be applied to detecting that the speed has exceeded a predetermined value. In this case, the output A is low level when it is below a predetermined value,
Since it becomes a high level when it reaches a predetermined value or more, the rising edge thereof may be set as the detection point.

By the way, to change the detection speed of this speed detection circuit,
It is only necessary to change the time constant τ11 of the Ridrigger type monostable multi-bibreak (2). Conventionally, commonly used 1
In the case of a monostable multi-bi break configured using a pair of transistors, the time constant τi can be changed by changing the time constant of a time constant circuit consisting of a resistor and a capacitor or by changing the power supply voltage for this mono-stable multi-bi break. However, in these methods, when the power supply voltage is changed, the time constant changes in response to changes in voltage.

Furthermore, when changing the resistance of the time constant circuit, for example, the time constant does not correspond linearly to this change in resistance. For this reason, when the set value of the detection speed is scaled, the set value is not scaled linearly, resulting in an unsightly scale. Further, in this case, depending on the purpose, it is better to display the period T of the input pulse, or it is better to display the frequency f of the manual pulse. However, since the relationship between the two is f=1, which is a reciprocal relationship, if one were to be scaled linearly, the other would become a hyperbolic scale.

Purpose of the Invention The present invention is a monostable multi-bi break suitable for use as a ridrigger type monostable multi-bi break (2) in a speed detection circuit configured as described above. In addition, when the time constant is made to correspond to the period and frequency, the purpose is to provide a system that allows the period and frequency to be changed linearly with respect to the time constant angle variable voltage. It is.

Summary of the Invention The invention consists of an integrating circuit composed of an operational amplifier, a switching element for resetting the integrating circuit, and a comparison circuit for comparing the output of the integrating circuit with a reference potential, and the switching element is controlled by input pulses. The integrator circuit is reset, and the slope of the integrated output is changed by changing the voltage applied between the inverting and non-inverting input terminals of the operational amplifier constituting the integrator circuit, or the reference voltage of the comparator circuit is changed. is a monostable multibibreak whose time constant is changed by changing the time constant. This invention uses an operational amplifier in the integrating circuit, so
The slope of the integrated output voltage is linear, so when the time constant is made variable as described above, the change in voltage that changes the time constant can be made to correspond linearly to the period or frequency of the input pulse. be.

Embodiment Hereinafter, an embodiment of the monostable multi-pipe brake according to the present invention will be described with reference to Fig. C, taking as an example the case where the monostable multi-pipe brake according to the present invention is used in the monostable multi-pipe brake of the speed detection circuit described above.

In Fig. 3, °ζ, (20) indicates a monostable multi-bi break, which consists of an integrator circuit (21) and a comparator circuit (22).
It consists of. Integrating circuit (21) is operational amplifier (210)
is used and configured. In other words, this operational amplifier (
The non-inverting input terminal of the variable resistor (210) is grounded, and the inverting input terminal is connected to the movable element of the variable resistor (112) via a resistor (211). One end of this variable resistor (212) is grounded, and the other end is a negative DC voltage, for example, a -15V power supply terminal (
11).

Further, a capacitor (213) is connected between the output terminal and the inverting input terminal of the operational amplifier (210), and
The source and drain of an FET (214) serving as a short switch is connected in parallel with this capacitor (213). Therefore, the output voltage Eo (Fig. 4C) obtained at the output terminal of the operational amplifier (210) is
212), and the time constant determined by the resistor (211) and capacitor (213).
It rises from ■, and when FET (214) is turned on, QV
Return to

FET (214) receives the input pulse P to be measured as follows:
It is turned on at the time f (FIG. 4A). That is,
The input pulse Pf through the input terminal α0) is 079717
It is supplied to the clock terminal of the 071 circuit (13). On the other hand, the D terminal of this 079717071 circuit (13) has
The output of this flip-flop circuit (13) is supplied and kept at a high level. Therefore, when the pulse Pf is input, its Q output PF (Fig. 4B) goes to a high level. Stand up. Then, resistance (1
As the capacitor (15) is charged through 4), the potential at the connection point between the resistor (14) and the capacitor (15) rises, which clears the 079717071 circuit (13) and causes the Q output P to go to low level. I will judge. In other words, the output pp of the 079717071 circuit (13) is synchronized with the input pulse Pf, and the pulse width is determined by the time constants of the resistor (14) and the capacitor (15). This pulse pp then passes through the resistor (16) to the FET (
214), and this FET (214) is turned on during the pulse width period of pulse PF.

As mentioned above, the output voltage Eo of the operational amplifier (210) is a voltage that increases at a constant slope until this FET (214) is turned on, so this voltage EO depends on the input pulse P.
The level is proportional to the period length of f. This output voltage Eo is applied to the operational amplifier (220) constituting the comparator circuit (22).
) is supplied to the non-inverting input terminal of this operational amplifier (22
0) is compared with the reference voltage θV supplied to the inverting input terminal of the operational amplifier (220
), i.e. the monostable multipipe rake (20)
The output Mα (FIG. 4D) becomes low level. In other words, the time constant of the monostable multipipe rake (20) is determined by the slope of the output voltage Eo of the integrating circuit (21) and the comparator circuit (22).
) is determined by the reference voltage θV for comparison, and when the period of the input voltage pulse Pf becomes longer than the time constant of this monostable break (20), the output MQ becomes a low level. The reference voltage θV is a positive DC voltage, for example +15V.
A variable resistor (2) connected between the power supply terminal (12) and ground
21).

The output M1;L of the monostable multi-bi break (20) thus obtained is 079712 as shown in FIG.
In the 071 circuit (30), the 079712071 circuit (
13) sampled by pulse PFy from
The output FQ (Fig. 4E) is AND gated with the output Mct in an AND gate (40) consisting of diodes (41) and (42), and the output Ao (opening F
), the drive transistor (51) is turned on and, for example, the stop control plunger (50) is driven.

In addition, in order to prevent the speed detection circuit from working when the belt conveyor, etc. whose speed should be detected starts up, in the example shown in the figure, the high-level signal is not activated until the belt conveyor, etc. starts up to a predetermined reference speed. It is supplied to the preset terminal of the 079712071 circuit (13) through the terminal (17) and is also supplied to the D flip-flop circuit (3).
0) is supplied to the clear terminal. Therefore, 0797
During that time, the output PP of the 12071 circuit (13) is set to a high level, the FET (214) is turned on, the integrating circuit (21) is turned off, and the 079712071
During this period, the output FQ of the circuit (30) is always kept at a low level, and the AND gate output Ao never becomes a high level.

Further, in the illustrated example, a circuit is provided to indicate that the input pulse Pf is being supplied to the circuit. That is, the resistor (18) and light emitting diode (1) connected between the power supply terminal (12) and the D terminal of the 079712071 circuit (13)
In the series circuit 9), when the pulse PI is supplied to the D flip-flop circuit vR (13) through the input terminal 0, its Q output is at a low level for the pulse width period of the pulse PP, so it emits light during that period. This is displayed when the diode (19) lights up.

By the way, the period or frequency of the detected pulse Pf can be changed by the time constant of the monostable multipipe rake (20).

The time constant of the monostable multivibrator (20) changes as the position at which the integrated voltage Eo exceeds the reference voltage θV changes.

This position can be changed by changing the reference voltage θV and by changing the slope of the integral voltage Eo.

The reference voltage θV can be changed by changing the resistance value of the variable resistor (22]), and since the voltage Eo increases linearly, increasing the voltage θV by n times also increases the detection period by n times. In other words,
Since a change in the detection period can be replaced by a change in voltage θV, if a B-type variable resistor (221) whose resistance value changes linearly with the amount of sliding is used, this variable resistor (221) The linear change in the amount of sliding of the slider can be calibrated as the detection period.

On the other hand, the slope of voltage Eo is changed by voltage RV, and this voltage RV is changed by changing the resistance value of the variable resistor (212). When the straight line of voltage Eo is expressed as a function,
Eo-k t (, , j is time), and the value of k representing the slope becomes 2, for example, when the voltage RV is doubled. In other words, the C area changes linearly in response to the voltage upper pattern 1. Therefore, if the variable resistor (212) is of type B, the slope of the voltage Eo changes linearly in response to the change in resistance, and as explained below, the change in resistance is caused by the change in frequency. It can be expressed as

That is, in FIG. 5, the solid line (
6) state (Eo=kt) to the solid line (7) state (go
-Nk t). At this time, the value of the threshold voltage due to the voltage θV is
Then, the time when the voltage Eo exceeds this value is C
and d. On the other hand, if the respective levels after a certain time C have passed are a and b, the following relationship holds true.

x a x b c o de · ° · ac = bd b c a d . This indicates that when the slope increases by N times, the period increases by 1, that is, the frequency increases by N times. Therefore, the voltage Rv, that is, the change in the resistance value of the variable resistor (212) linearly corresponds to the frequency change, and the linear change in the amount of sliding of the variable resistor (212) can be calibrated as the detection frequency. For example, as shown in Figure 3, a variable resistor (212)
By supplying the voltage obtained at , that is, the voltage between the re-input terminals of the operational amplifier (210) to the digital voltage display (60), the frequency can be digitally displayed in accordance with the voltage change.

Effects of the Invention As described above, in this invention, a Ridriger type monostable multi-bi break is constructed by comparing an integrated voltage having a linear slope with a predetermined reference voltage using an integrating circuit consisting of an operational amplifier and a level comparing circuit. So,
The time constant of this monostable multi-by-break can be made variable by changing the reference voltage of the level comparison circuit.
Alternatively, this can be easily done by changing the slope of the integrated voltage. Since the integrated voltage has a linear slope, when the reference voltage is changed, the change in the time constant can be caused to correspond linearly to this voltage, and the slope of the integrated voltage can be changed linearly. When the time constant is changed, the change in the time constant can be made to correspond linearly with the frequency to the voltage that changes the slope.

Therefore, if the monostable multi-bibrake of the present invention is used in a speed detection circuit as in the above example, it becomes possible to display the detection period or detection frequency using a linear scale.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an example of the speed detection circuit, Fig. 2 is a waveform diagram for explaining the same, and Fig. 3 is an example of the case where the monostable multivibrator according to the present invention is used in the speed detection circuit of Fig. 1. The system diagram of FIG. 4 and FIG. 5 are diagrams for explaining the system. (20) shows the monostable multivibrator as a whole, (21) its integrating circuit, (22) its level comparison circuit, (210) and (220) operational amplifiers, (21)
1) and (213) are a resistor and a capacitor for configuring the integrating circuit (21), (212) is a variable resistor that changes the level of the integrated voltage, and (221) is a variable resistor that changes the reference voltage. .

Claims (1)

[Claims] It consists of an integrating circuit made up of an operational amplifier, a switching element for resetting this integrating circuit, and a comparison circuit that compares the output of this integrating circuit with a reference potential. The integrator circuit is reset, and the slope of the integrated output is changed by changing the voltage applied between the inverting and non-inverting input terminals of the operational amplifier constituting the integrator circuit, or the reference voltage of the comparator circuit is changed. A monostable multi-bibreak with variable time constant.