JPH08264094A - Relay output circuit with function of detecting discontinuity - Google Patents

Abstract

PURPOSE: To provide a relay output circuit having the function of detecting discontinuity. CONSTITUTION: This relay output circuit having the function of detecting discontinuity comprises a drive relay comprising two-pole C contacts; a load relay driven by the drive relay 1; a counter-electromotive-force preventing diode 3 connected in parallel with the operating coil of the load relay 2; a dc power supply 4 form which a work current is passed to the operating coil of the load relay; a current-limiter resistor 5; and a photocoupler 6 serving as a current detector. Even in the normal condition wherein the drive relay 1 is not turned on, a current is always passed through output wiring and monitoring of the output wiring is made possible through the detection of the current, so that when a discontinuity occurs it can be detected immediately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay output circuit,
In particular, it relates to detection of whether or not the output wiring is broken.

[0002]

2. Description of the Related Art Conventionally, a relay output circuit has not been provided with a function of detecting disconnection of an output line wiring.

[0003]

Therefore, when the output wiring is broken, even if a signal for operating the external device is output, but the external device does not operate, what is the cause? It was difficult to determine. The present invention has been made to solve the above problems, and an object of the present invention is to provide a relay output circuit with a disconnection detection function that detects disconnection by detecting a current flowing through an output wiring.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a load relay, a drive relay for driving the load relay, a DC power source for supplying a touching current to the load relay, and an inverse coil connected in parallel to an operation coil of the load relay. It consists of an electromotive force prevention diode and a current detection unit that detects the current flowing in the output wiring that connects the contact of the drive relay and the operation coil of the load relay.When the drive relay is on, the current detection unit changes from the DC power supply. If the drive relay is off by driving a load current through the operating coil of the load relay without passing through the
Preventing a moving current from flowing through the operation coil of the load relay by passing through the current detection unit and the counter electromotive force prevention diode, and detecting the current flowing through the output wiring without driving the load relay. It is characterized in that the disconnection of the output wiring is detected by.

[0005]

According to the present invention, even when the drive relay is not turned on, a current is always supplied to the output wiring, and the output wiring can be monitored by detecting this current. Can detect disconnection.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a relay output circuit with a disconnection detecting function according to an embodiment of the present invention. In FIG. 1, 1 is a drive relay having a 2-pole C-contact configuration, 2 is a load relay driven by the drive relay 1, and 3 is a counter electromotive force prevention diode connected in parallel to an operation coil of the load relay 2. Reference numeral 4 is a DC power source for supplying a sensitive current to the operation coil of the load relay, 5 is a current limiting resistor, and 6 is a photocoupler which is a current detector.
Reference numeral 7 is an alarm display section that is not directly related to the disconnection detection function additionally provided and that causes a buzzer to sound as a disconnection alarm and causes a lamp to blink if a disconnection occurs as a result of detection by the photocoupler 6.

As shown in FIG. 1, the + side of the DC power source 4 has N01, which is the A contact of the first pole of the drive relay 1, and B of the second pole.
NC1 which is a contact point, C1 which is the C contact of the first pole of the drive relay 1 is on the cathode side of the back electromotive force prevention diode 3, and the anode side of the back electromotive force prevention diode 3 is on the drive relay 1
C2 which is the C contact of the second pole of the DC power source 4, the negative side of the DC power source 4 is NO2 which is the A contact of the second pole of the driving relay 1, the cathode of the light emitting diode section of the photocoupler 6, and the light emitting diode section of the photocoupler 6. Has an anode at one end of the current limiting resistor 5 and the other end of the current limiting resistor 5 at the first end of the drive relay 1.
It is connected to NC1 which is the B contact of the pole. The light receiving transistor section of the photocoupler 6 is connected to the alarm display section via an appropriate interface.

Next, the operation of such a relay output circuit with a disconnection detecting function will be described. The disconnection detection is realized only when the drive relay 1 is off. If there is no break in the output wiring, the DC electromotive force 4 biases the back electromotive force prevention diode 3 in the forward direction, so that the current passes through the back electromotive force prevention diode 3 and the current limiting resistor 5 to generate the photo current. The photo coupler 6 is turned on by flowing through the light emitting diode portion of the coupler 6. In this case, since no wire breakage has occurred, the buzzer of the alarm display unit 7 does not ring and the lamp does not blink. The reason why there is no disconnection in the output wiring when the photocoupler 6 is turned on is that the disconnection can be detected only when the operation of all the constituent elements of the disconnection detection circuit is normal. However, if there is an abnormality in the operation, a disconnection is issued to warn of an abnormal operation of the detection circuit.

On the contrary, when the output wiring is broken, the photocoupler 6 does not turn on because no current flows from the DC power supply. Therefore, the photocoupler 6 detects the disconnection of the output wiring. In this case, the alarm display unit 7 operates, sounds the buzzer, blinks the lamp, and issues a disconnection alarm. As described above, since the counter electromotive force preventing diode 3 is biased in the forward direction, no current flows through the operation coil of the load relay 2 even if a current flows through the output wiring, so the load relay 2 cannot be turned on. Therefore, the corresponding field equipment will not be affected. On the other hand, when the drive relay 1 is turned on, if there is no disconnection in the output wiring, an exciting current flows from the DC power source 4 to the operation coil of the load relay 2, the load relay 2 is turned on, and the corresponding field device is operated by the drive relay 1. You can control.

[0010]

According to the present invention, as described above,
Even when the drive relay is not normally turned on, a current is always passed through the output wiring, and the output wiring can be monitored by detecting this current. Therefore, when a disconnection occurs, the disconnection can be detected immediately. Further, since the disconnection can be detected, it becomes easy to investigate the cause when the corresponding field device does not operate even though the drive signal is output. Therefore, maintenance is facilitated and reliability is improved.

[Brief description of drawings]

FIG. 1 is a relay output circuit with a disconnection detecting function according to an embodiment of the present invention.

[Explanation of symbols]

 1 Drive relay 2 Load relay 3 Counter electromotive force prevention diode 4 DC power supply 5 Current limiting resistor 6 Photocoupler 7 Alarm display

Claims (1)

[Claims] 1. A load relay, a drive relay for driving the load relay, a DC power source for supplying an exciting current to the load relay, a back electromotive force preventing diode connected in parallel to an operation coil of the load relay, and a drive. It consists of a relay contact and a current detector that detects the current flowing in the output wiring that connects the operation coil of the load relay.When the drive relay is on, the load relay does not go through the current detector from the DC power supply. When a load relay is driven by sending a touching current to the operation coil of, and the drive relay is off, a touching current flows to the operation coil of the load relay via the current detection unit and the counter electromotive force prevention diode. The disconnection detector is characterized in that the disconnection of the output wiring is detected by detecting the current flowing in the output wiring with the current detection unit without driving the load relay. Per relay output circuit.