JPH0551131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a circuit for detecting the energized excitation state of an AC relay and supplying the detected state to a signal input circuit or the like used in a microcomputer via an isolator circuit.

BACKGROUND TECHNOLOGY In various industrial fields, predetermined equipment machines that are electrically driven are activated or deactivated depending on various conditions, and for this purpose, usually an AC relay is used to control the energization of the equipment machine, and Multiple pairs of contacts (relay contacts, pushbutton switches, limit switches,
(others) are used. For example, in Fig. 8, RY is an AC relay that has a switch SW for disconnecting the target equipment (not shown), and has multiple pairs of contacts connected in series to this relay and connected in parallel to each other. Among them, contact 1 is a relay contact from another control relay, 2 is a pushbutton switch contact, and 3 is a limit switch. When any of these contacts is closed, relay RY is energized and switches SW.
It opens or closes the . In such a circuit, if the power to the target equipment is turned off or turned off (or started) under some conditions, in order to perform accurate recording or control, it is necessary to know what the conditions are, that is, which contact points are used to connect the relay. It is necessary to know when is energized and excited.

Therefore, in a circuit like the one shown in Figure 8, if there is room in terms of specifications or structure, and if the circuit can be designed from the beginning or if the existing circuit can be modified, these contacts can be connected as shown in Figure 9. 1, 2 and 3 are interlocking - multi-pole (multi-circuit) contacts, relay RY
Sub-circuit contacts 1b, 2b and 3b corresponding to main circuit contacts 1a, 2a and 3a for energization are inserted into an interface circuit of a microcomputer, for example, for actuation detection, and have an isolator function for the main contact circuit. A circuit can be constructed. In this case, it must be noted that signal input circuits such as microcomputers are extremely sensitive to noise from AC power supplies.

Problem to be Solved by the Invention However, in the circuit shown in Fig. 9, the excitation current of the AC relay RY is not directly detected, but if each sub-contact closes, the main contact in the relay circuit also closes. This is nothing but an indirect detection method that assumes that the AC relay RY will be energized and energized. Therefore, if the interlocking relationship between the main contact and the sub contact is not established due to a failure of each condition switch, etc., a problem arises in that the energized and excitation state of the AC relay is not accurately transmitted to the signal input circuit of the microcomputer, etc. . Therefore, AC relay RY
If this is a stop relay for a device that requires strict sequence control, etc., and each switch contact is arranged for each stop factor, the energization and excitation of this AC relay RY itself should be used instead of the indirect method described above. should be detected directly. In addition, when transmitting relay energization and excitation to a microcomputer, etc., even if there are specifications or structural restrictions that prevent the adoption of a double contact method as shown in Figure 9, relay energization and excitation can be Direct detection is required.

On the other hand, when configuring a circuit that directly detects which contact is used to excite an AC relay,
The detection signal must be accurately transmitted to digital equipment and microcomputer application equipment without being affected by electromagnetic interference (EMI) from AC power sources.

The purpose of the present invention is to directly control the switch contacts (on/off conditions) that contributed to the energization and excitation of the AC relay.
It is an object of the present invention to provide a circuit for detecting the relay circuit accurately and without affecting the relay circuit.

Means for Solving the Problems In achieving the above object, the present invention provides an AC circuit including at least one switch contact branch for energizing and excitation of an AC relay, in which one switch contact is connected in series with the AC relay. a first diode inserted at the crossroads; a second diode connected in parallel with the AC relay with a polarity opposite to that of the first diode; an isolator input element connected to be energized in polarity; and an isolator signal output electrically isolated from the alternating current circuit that is driven by the isolator input element to produce a signal output for indicating the energized state of the alternating current relay. This is an excitation energization detection circuit for an AC relay characterized in that it is equipped with a circuit.

The invention also provides a detection circuit including a processing circuit for generating a substantially constant amplitude status signal in response to the output signal of the isolator signal output circuit.

Operation According to the above basic configuration, the AC relay is excited by the positive (for example, the rectification direction of the first diode is set to "positive") half-wave energy of the AC power supply, and the AC relay The isolator input element is activated during the negative half cycle short-circuited by the diode, and this activation state is transmitted to the isolator signal output circuit by physical means other than the electric circuit, and energization of the relay is detected. In this case, a simple and effective isolator system can be constructed by using a light emitting diode as the isolator input element and inserting a phototransistor which forms a photocoupler with the light emitting diode into the isolator signal output circuit. Since the signal output taken out from the isolator signal output circuit is electrically isolated from the AC line 4, it is transmitted to the control circuit etc. without being affected by noise due to EMI or the like.

Furthermore, if the signal processing circuit of the present invention is connected to the isolator signal output circuit, the detection signal of energization excitation will not be a pulse train with a half cycle width of AC, but will continue with a constant amplitude, resulting in extremely stable and accurate detection output. can do.

Embodiment FIG. 1 shows the basic configuration of the present invention,
Relay RY and switch contacts 1, 2 and 3 are similar to the conventional one described in FIG. In the present invention, a detection main circuit, 5 in total, is inserted between the relay RY and each contact 1, 2, and 3.
The main detection circuit 5 includes a diode D1 inserted in series between the relay RY and the corresponding switch contact.
, an isolator input circuit 6 connected as a parallel shunt of this diode D1, an isolator signal output circuit 7 driven by a signal other than current from this isolator input circuit 6, and a signal output of this signal output circuit 7 is processed. It consists of a signal processing circuit 8. A diode D2 is connected in parallel to the relay RY with a polarity opposite to that of the diode D1. The detection main circuits 5a and 5b connected between the relay RY and the contacts 2 and 3, respectively, have the same circuit configuration as the main circuit 5.

FIG. 2 shows an embodiment of the main detection circuit 5, in which the isolator input circuit 6 includes a light emitting diode 6.
The isolator signal output circuit 7 includes the light emitting diode 6a, a phototransistor 7a forming a photocoupler, and a current limiting resistor R1 connected in series with the isolator signal output circuit 7. The collector of this phototransistor 7a is connected to the signal processing circuit 8.

In the configuration shown in FIG. 2 described above, when contact 1 closes, the forward direction of diode D1 becomes a positive half cycle, and at this time, current flows from the AC power supply to AC relay RY through diode D1 and contact 1,
At the same time, a reverse voltage is applied to the parallel diode D2 of the relay RY and the light emitting diode 6a as an isolator input element, so that no current flows. In the next half cycle when the polarity of the AC power source is reversed, the diode D
1 is in the opposite direction, but the diode D2 and the light emitting diode 6a are in the forward direction, and the light emitting diode 6
This half-wave AC voltage is substantially applied to the series circuit of a and the current limiting resistor R1, and the current is applied. Therefore, the light emitting diode 6a emits light to drive (irradiate) the phototransistor 7a, and a substantially square wave signal as shown in FIG. 3a is generated at the collector terminal of the phototransistor. On the other hand, in this half cycle, the AC relay RY is short-circuited by the parallel diode D2, and the energy accumulated in the previous half cycle is released and distributed, suppressing the surge.

In other words, without the parallel diode D2, no effective half-wave current of negative polarity will flow, and the relay RY will essentially receive only half-wave rectification by the diode D1, and the excitation coil of this relay will be attracted during the negative half cycle. The force becomes zero, a restoring force is applied, and the device operates again in the next half cycle, which may cause chattering. However, if the diode D2 is connected in parallel to the AC relay RY according to the present invention, the surge current will flow through the diode D2 before the AC relay returns, creating a flywheel effect, which will reduce the time it takes for the AC relay to return. It will be delayed and proceed directly to the next positive half cycle.

Generally, in AC relays, a shaded coil is installed in a part of the magnetic pole, and the phase difference between the magnetic flux generated here and the main magnetic flux is used to average out the attractive force, which also adds to the delay in return time. Therefore, due to these comprehensive effects, the AC relay maintains its holding state even in the negative half cycle when it is disconnected from the power supply. On the other hand, the energization state of the AC relay RY is supplied to the signal processing circuit 8 from the collector of the phototransistor 7a as a pulse train generated every negative half cycle of the AC power supply.

As shown in FIG. 4, one embodiment of the signal processing circuit 8 using an analog system includes an input-side waveform shaping circuit made of, for example, a CMOS logic circuit connected to the input terminal, that is, the collector terminal C of the phototransistor 7a. It consists of a Schmitt inverter 9, an integration circuit 10 for integrating the waveform shaping output of the Schmitt inverter 9, and a Schmitt inverter 11 as an output side waveform shaping circuit that receives the output of the integration circuit 10 via a latch-up protection resistor R5. ing. The integrating circuit has a resistor R3 connected between its input and output, a series circuit of a resistor R4 and a diode D3 connected in parallel to this resistor R3, and a parallel circuit consisting of R3, R4, and D3 that is connected to the ground potential as a charging resistor. capacitor C connected between
1. Each circuit constant is rd<<R4 and R4<<R3, where the internal resistance of diode D3 is rd. Therefore, (R4+rd)<<R3 And the charging time constant is τc=(R4+rd)・R3/(R4+rd)+R3・C1 ≒ R4・R3/R3・C1=R4・C1. When the input to the integrating circuit 10 changes from a high level voltage to a low level voltage and the capacitor C1 is discharged, the diode D3 is cut off, and therefore only R3 exists in the discharge path. The discharge time constant τd is τd=R3・C1. In other words, τc≪τd,
A network is formed in which charging occurs rapidly with a relatively small time constant, while discharging occurs slowly with a relatively large time constant. Therefore,
The input signal waveform to the integrating circuit 10 shown in FIG. 3b becomes an output signal waveform having a wavy high level as shown in FIG. 3c. This output waveform is supplied to the output side Schmitt inverter 11 via the latch-up protection resistor R5, and becomes a negative rectangular wave signal as shown in FIG. 3d. Thereby, the energization excitation by a predetermined switch contact of the AC relay RY is identified by detecting a stable output waveform without being mixed with noise.

Note that the latch-up protection resistor R5 is not necessary when the output side waveform shaping circuit is a logic circuit such as LS-TTL. In addition, since the charging time constant τc (Fig. 3c) is short in this analog signal processing circuit, the contact 1 quickly detects the energization and excitation of the relay RY, and as described above, the smoothing effect of the integrating circuit 10 allows the microcomputer to A stable output with noise components eliminated can be obtained as an input to the control circuit. As shown in FIG. 5, when the phototransistor 7a of the isolator signal output circuit is used as an emitter follower, the signal processing circuit 8 is configured as a circuit 10' in which the polarity of the diode D3 in the integrator circuit 10 is reversed, and the input/output side is The compatible Schmitt inverter 9', 1
1', the circuit network will have a discharging time constant smaller than the charging time constant, and therefore a signal whose polarity is inverted from that of FIG. 3d can be extracted.

A preferred embodiment in which the signal processing circuit 8 in FIGS. 1 and 2 is of a digital type is shown in FIG. In the circuit 8' of FIG. 6, the input Schmitt inverter 9 is similar to that of FIG. 4, but the output of the inverter 9 is fed to the trigger input B of a retriggerable monostable multivibrator 12. A of this monostable multivibrator
The input is connected to a Vcc level voltage as shown or to ground potential. The Q output is connected to the Schmitt inverter 13 on the output side. In addition, the reset signal circuit 14 is connected to the reset RD terminal.
is connected, and the time constant terminals “CX” and “RX” are connected to Vcc.
Capacitor connected between level and ground potential
Connected to both ends of CX in a series circuit of CX and resistor RX. The output pulse width tw of this monostable multivibrator 12 is CX and RX
By setting the pulse width tw to a time longer than the AC power cycle, the pulse train that is input one after another to the Schmitts inverter 9 every cycle of the AC power will retrigger the multivibrator 12. to extend the output pulse width, and the Q output is not interrupted during this period. Therefore, a pulse input as shown in FIG. 7a becomes a continuous signal of constant amplitude as shown in FIG. 7b.

According to the above-mentioned digital signal processing circuit, since an analog integrating circuit is not used, there is no delay time until the threshold voltage of the output-side Schmitt inverter 13 is reached.
It is possible to construct an isolator circuit that detects excitation energization of an AC relay with a shorter delay time for opening and closing the contact 1 shown in the figure.

Effects of the Invention As described above, the present invention detects which contact is activated in the energizing excitation circuit of an AC relay while the influence of noise from the AC power source is substantially eliminated by the isolation function. The detection signal can preferably be supplied to a signal input section of a control circuit using a microcomputer or the like. In the example, an optical coupling system consisting of a light emitting diode and a phototransistor was used as an isolator system;
A similar configuration can be made using MOSFET type elements.

Furthermore, analog or digital signal processing circuits play an important role in stabilizing detection signals when they are supplied to control equipment, but in some cases, it is not possible to use these signal processing circuits. It is also possible to directly use the output of the isolator signal circuit as an input to the control circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a basic embodiment of the present invention, FIG. 2 is a circuit diagram showing main parts of the basic embodiment,
Figures 3 a to d are diagrams showing waveforms at each stage of detection and signal processing, Figure 4 is a circuit diagram showing an embodiment of the analog signal processing circuit, and Figure 5 is a diagram showing another embodiment of the analog signal processing circuit. 6 is a circuit diagram showing an embodiment of a digital signal processing circuit, and FIG. 7 is a circuit diagram showing an embodiment of a digital signal processing circuit.
Figures a and b are diagrams showing signal waveforms at the input and output parts of a digital signal processing circuit, Figure 8 is a circuit diagram showing a conventional relay energizing circuit to which the circuit of the present invention is applied, and Figure 9 is a circuit diagram of a conventional relay energizing circuit to which the circuit of the present invention is applied. FIG. 7 is a diagram illustrating a trial relay energization circuit with an energization circuit detection contact; RY...AC relay, 1...Relay contact, 2...
...Push button switch contact, 3...Limit switch, 4...AC circuit, 5...Main circuit for detection, 6...
...Isolator input circuit, 6a...Light emitting diode, 7...Isolator signal output circuit, 7a...
Phototransistor, 8...Signal processing circuit, 9...
...Input side Schmitt inverter, 10... Integrating circuit, 11, 13... Output side Schmitt inverter, 12... Retriggerable monostable multivibrator, 14... Reset signal circuit.

Claims (1)

[Claims] 1. At least one for energizing and excitation of an AC relay.
In an AC circuit including a switch contact branch of the circuit, a first diode inserted in one switch contact branch in series with the AC relay and the first diode in parallel with the AC relay are connected with opposite polarity. a second diode connected to the first diode, an isolator input element connected in a parallel branch of the first diode so as to be energized with a polarity opposite to that of the diode, and driven by the isolator input element to determine the energization state of the AC relay. An isolator circuit for detecting excitation energization of an AC relay, comprising an isolator signal output circuit electrically isolated from the AC circuit that generates a signal output for indicating. 2. The circuit of claim 1, further comprising processing circuitry for generating a substantially constant amplitude status signal in response to the output signal of said isolator signal output circuit.