JPH0898260A - Interface circuit - Google Patents

Abstract

PURPOSE: To dispense with the installation of a power source line for a detector and to check a normal coupling state between the detector and a controller and the normal operating state of the detector. CONSTITUTION: The detector 1 is coupled with the controller 3 with 1 7 signal lines 5, 6, and an interface circuit 4 applies a DC to the signal lines via a resistor, and takes out the on/off voltage change of the signal line to a photocoupler PC as a detection signal from the detector and a check signal for normal coupling state with a detector side. An interface circuit 2 performs the on/off driving of the signal line via an AND circuit A and a transistor T1 by the signal of an oscillator OSC in a state in which no detection output is issued from a detector main body, and also, fetches a DC power to a capacitor C by charging from a controller side via the signal line in the off-driving period of the signal line. The normal coupling state of the detector with the controller and the normal operating state of the detector can be judged by the existence of the on/off driving of the signal line, etc., on a controller side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interface circuit for connecting a detector and a controller in a disaster prevention system or the like.

[0002]

2. Description of the Related Art In a disaster prevention system, detectors such as smoke detectors and temperature detectors are dispersed and arranged in various parts of a building, and a detection signal from these detectors is received by a controller in a monitoring room to give an alarm. Signal generation and automatic activation of disaster prevention equipment. Similarly, in a security system, an alarm signal is obtained by combining a controller with a large number of detectors for detecting an intruder or the like.
Further, various sensors and controllers are coupled to various control systems such as a sequence controller, and the operation sequence of the control device is switched and the control amount is adjusted according to a signal from the sensor.

An interface circuit for coupling each detector to a controller is generally provided with a circuit for putting an ON or OFF signal on a signal line according to the detection of the detector on the detector side, and the controller side outputs this signal. A receiving circuit is provided.

In these systems, the power supply method required for the detectors is as follows: a terminal for commercial power supply is placed at the location where each detector is installed, and commercial power is supplied from the terminal to the detector. There is a method of providing a power supply terminal to the detector and wiring to each detector.

[0005]

Each of the conventional power supply methods requires the installation of a power supply line up to the detector installation site, and a system having a large number of detectors requires a high construction cost for power supply installation. Will be needed. In addition, large-scale construction is required to install new detectors and change their positions.

On the other hand, in the conventional interface circuit, since the ON / OFF signal is transmitted and received between the detector and the controller, whether or not the detector including the signal line can be normally operated. There is a problem that reliability is poor because there is no function to check.

For example, when the detector side interface circuit generates a normally open a-contact signal, the controller side cannot check the occurrence of disconnection of the signal line and cannot receive a signal indicating that the detector has operated.

On the contrary, when the interface circuit generates a normally closed b-contact signal, the controller side cannot check the occurrence of a short circuit in the signal line and cannot receive the operation signal of the detector.

It is an object of the present invention to provide an interface circuit which eliminates the need for laying the power line of the detector.

Another object of the present invention is to provide an interface circuit capable of checking the normal coupling state between the detector and the controller and the normal operating state of the detector.

[0011]

To solve the above problems, the present invention provides an interface circuit for coupling a detector and a controller with a signal line, wherein the interface circuit of the controller applies a direct current to the signal line. Then, the on / off voltage change of the signal line is taken out as a detection signal from the detector and a normal coupling state check signal with the detector side, and the interface circuit of the detector has a detection output from the main body of the detector. When there is no output signal, the signal line is turned on / off by the oscillation signal, and DC power is taken in from the controller side through the signal line during the off-driving period of the signal line, and a detection output is generated from the detector body. It is characterized in that it has a circuit configuration for driving the signal line off.

[0012]

The signal line connecting the detector and the controller is used as a power supply line from the controller to the detector side.

For this power supply, the detector side drives the signal line on / off during normal operation, turns off the signal line during the detection operation, and supplies power during the period during which the detector side drives the signal line off. .

Further, the normal coupling state between the detector and the controller and the normal operating state of the detector are determined on the controller side from the presence / absence of ON / OFF driving of the signal line.

[0015]

1 is an interface circuit diagram showing an embodiment of the present invention. 1 is a detector such as a smoke detector, a temperature detector, a fire detector, etc. to which the interface circuit according to the present invention is applied. 2 is an interface circuit on the detector 1 side. Three
Is a controller to which the interface circuit according to the present invention is applied. Reference numeral 4 denotes an interface circuit on the controller 3 side, which shows an example in which a 24V DC power supply is used.

Reference numeral 5 is a 0 V (common line) side of a signal line connecting the detector 1 and the controller 3, and 6 is a signal side of the signal line.

Reference numeral 7 is a main body of the detector 1, and if the detector 1 is a smoke detector, it is a smoke detecting section using a phototransistor, and the terminal a changes to a low level when smoke is detected. I shall.

If the detector 1 is a temperature sensor, the detector body 7 is a temperature detecting section using a temperature sensor IC and the like, and when the temperature reaches the set temperature, the terminal a changes to the low level. It shall be.

Further, if the detector 1 is a fire detector,
The detector body 7 is a fire detector having a normally open contact, and when the temperature reaches a certain temperature, the contact is closed and the terminal a changes to a low level.

If the detector 1 is a fire detector, it is not necessary to supply power to the fire detector, so the detector terminal + p
Connection is not required.

Reference numeral 8 denotes a light projector required when the detector 1 is a smoke detector, and generates pulsed light for irradiating the light receiving portion of the detector body 7 so that the detector body 7 can detect smoke. To do. In a temperature sensor or a fire sensor that does not require the floodlight 8, its terminals s and t are short-circuited.

Interface circuit 4 on the controller 3 side
The PC is a photo coupler. R1 is a resistor that determines the input current value of the photocoupler PC when the signal line 6 of the interface circuit changes to low level. R2 is a resistor for increasing the noise margin. R3 is a resistor for forming a circuit that supplies DC power from the + 24V power source to the detector 1 side through the signal line 6 when the signal line 6 is at a high level.

The ON / OFF signal of the photocoupler PC is taken out from the terminals u and v and transmitted to the main body circuit in the controller 3 to detect the occurrence of disconnection / short circuit of the signal lines 5 and 6 on the controller 3 side and the detector. The signal is used to determine the presence or absence of the operation 1 and the normal state.

The terminal t of the interface circuit 2 on the detector 1 side is connected to the signal line 6 through the projector 8 when the projector 8 is provided, and is connected to the signal line 6 when the projector 8 is not provided. Directly connected.

T1 of the interface circuit 2 is a transistor, which controls the signal line 6 to a low level by an on operation and sets the signal line 6 to a high level by an off operation regardless of the type of the projector 8.

C of the interface circuit 2 is a capacitor, which controls the controller 1 while the signal line 6 is at a high level.
The DC power supplied from the side is stored. D is a diode, which allows the signal line 6 to go low when the transistor T1 is on. T2 is a transistor for constant voltage control, ZD is a Zener diode, and R1 is a resistor. These circuit elements T2, ZD,
R1 constitutes a constant voltage circuit, and obtains a stabilized voltage output from the terminal voltage of the capacitor C as the power supply terminal + p to the oscillator body 7 and the power supply + p of the internal circuit.

The OSC of the interface circuit 2 is a pulse oscillator, and the oscillation signal is output to the terminal b. A is 2
It is an AND circuit of the input, the detection signal (usually high level) from the detector body 7 is input to one input terminal a, and the pulse signal from the oscillator OSC is input to the other input terminal b and output. An on / off signal for driving the transistor T1 is obtained from the terminal c. Therefore, normally, the transistor T1 is repeatedly turned on and off at the frequency of the oscillator OSC, and is controlled to be in the off state when the detector body 7 performs the detection operation (changes to the low level).

A concrete circuit example of the oscillator OSC is shown in FIG. In the figure, a programmable unijunction transistor PUT is used, and its terminal A is an anode, K is a cathode, and G is a gate. R1-R
4 is a resistor and C is a capacitor. Resistor R1
And R2 determine the gate potential, capacitor C and resistor R
3, the charging time constant of the capacitor C is determined, and the resistor R4 is for discharging the capacitor C when the PUT is turned on.

The oscillation frequency of the oscillator OSC is substantially determined by the charging time constant by the gate potentials C and R3, the potential at the point b is low level when the PUT is off, and the charge of the capacitor C is turned on when the PUT is on. It goes high while discharging at R4.

An oscillator of another system, such as an astable multivibrator circuit or a crystal oscillator circuit, can be used as the oscillator OSC.

A specific circuit example of the AND circuit A is shown in FIG. The figure shows the case where a diode logic circuit is used, where R1 is a resistor and D1 to D3 are diodes. AND operation is performed by the resistor R1 and the diodes D1 and D2,
The potential at point a is high level when the AND condition is satisfied,
It goes low when not established. The diode D3 is
The noise margin when driving the transistor T1 of the next stage with the terminal C is increased.

Note that another AND circuit, for example, a DTL circuit, a TTL circuit, or a C-MOS circuit can be used as the AND circuit.

The operation of this embodiment will be described. First, when the + 24V power source is established by turning on the power of the controller 3, the resistor R3 of the interface circuit 4 → the signal line 6
Power is supplied to the detector 1 through the. As a result, the capacitor C in the interface circuit 2 is charged, and the stabilized power supply circuit (T2, ZD, R1) supplies constant-voltage power to the detector body 7, the oscillator OSC, and the AND circuit A.

By this power supply, the detector body 7 starts the detecting operation, and the oscillator OSC starts oscillating. Here, in a normal state where the detector main body 7 is not in the detection state, its terminal a is at a high level, so that the pulse output of the oscillator OSC drives the transistor T1 to turn on / off through the AND circuit A, and the projector 8 turns on. -Off driving and high-level / low-level driving of the signal line 6 are performed.

As a result, the photocoupler PC of the interface circuit 4 on the controller 3 side is turned on / off,
The on / off signals from the output terminals u and v are taken into the controller 3, and the detection processing means (for example, a microcomputer) of the controller 3 checks that the detector 1 is operating normally, and the signal line. Check that there is no disconnection / short circuit in 5 and 6, and check that the detector body 7 is in the normal state where it is not in the detection state.

It should be noted that the disconnection of the signal line is judged from the fact that the output of the photocoupler PC remains off, or the detector 1
The determination is made by cutting off the power supply current to the side, or by the simultaneous establishment thereof. In addition, the short circuit of the signal line
The determination is made based on whether the output of the photocoupler PC remains on, the determination based on the excessive power supply current to the detector 1 side, or the determination based on their simultaneous establishment.

Next, when the detector main body 7 performs a detection operation and sets its output terminal a to a low level, the output of the AND circuit A is forced to a low level, the transistor T1 is turned off, and the signal line 6 is turned off. Set to high level. As a result, the output of the photocoupler PC of the interface circuit 4 on the controller 3 side is turned off, and it is determined by the detection processing means of the controller that the detection operation has occurred.

FIG. 4 shows circuit connections when the present invention is applied to a smoke detector. 1 to 8 and other symbols in the figure correspond to those in FIG.

The projector 8 required for the smoke detector is a light emitting diode D between the terminal t of the interface circuit 2 and the signal line 6.
Is provided.

As a result, the light emitting diode D is caused to emit light when the signal line 6 is brought to a low level by the ON operation of the transistor T1 of the interface circuit 2, and the power required for light emission which occupies most of the power consumption of the smoke sensor is supplied. Directly supplied from the controller 3 side. In addition, during the period when the transistor T1 is turned off and the signal line 6 is at a high level, power is supplied from the controller 3 side to the detector 1 side that charges the capacitor C in the interface circuit 2.

The detector main body 7 is a smoke detector main body, and is configured to detect scattered light of pulse emission from the light projector 8 due to smoke, or to detect that received light of pulse emission is attenuated by smoke. When smoke is detected, the terminal a is set to low level.

FIG. 5 shows a circuit connection when the present invention is applied to a temperature sensor. 4 is different from that of FIG. 4 in that the projector 8 is eliminated and the transistor T of the interface circuit 2 is eliminated.
The output terminal t of 1 is directly connected to the signal line 6, and the detector body 7 is used as a temperature detector such as a temperature sensor IC.

The temperature detector sets the terminal a of the detector body 7 to a low level when the temperature reaches or exceeds the set value.

FIG. 6 shows circuit connections when the present invention is applied to a fire detector. 5 is different from FIG. 5 in that the detector body 7 is a fire detector in which a ferromagnetic material and a normally open reed switch are combined, and since the detector body 7 does not require a power source, it is connected to the interface circuit 2. The point is that the connection of the power supply connection terminal + p is omitted.

When the fire detector reaches a certain level, the magnetic material is demagnetized, the reed switch is closed, and the terminal a is set to the low level.

In the embodiment, the interface circuit 4 on the side of the controller 3 can be appropriately modified in design for the circuit configuration for applying DC to the signal lines 5 and 6 and fetching ON / OFF signals.

Further, the interface circuit 4 on the detector 1 side
Can appropriately change the design of the configuration of the stabilized DC power supply and the configuration of the signal line drive.

[0048]

As described above, according to the present invention, in the interface circuit that connects the detector and the controller with the signal line, the interface circuit of the controller applies direct current to the signal line to turn on the signal line. The circuit configuration is such that the off-voltage change is extracted as the detection signal from the detector and the normal coupling state check signal with the detector side, and the interface circuit of the detector uses the oscillation signal line when there is no detection output from the detector body. Is turned on and off, DC power is taken in from the controller side through the signal line during the signal line off drive period, and the signal line is turned off when a detection output is generated from the detector body.
It has the following effects.

(1) Since the signal line connecting the detector and the controller is used as a power supply line from the controller to the detector side, special wiring for supplying the necessary power to the detector is unnecessary. . Along with this, it becomes easy to newly install or change the position of the detector and further change the installation plan of the detector.

(2) Since the signal line is normally turned on / off and turned off during the detection operation of the detector, the detector and the controller are normally connected including the disconnection / short circuit of the signal line and the detector. The normal operation state of can be determined on the controller side.

(3) Both the detector-side and controller-side interface circuits can be used as a common interface circuit for various sensors, and can be used for other detectors, and are highly versatile interface circuits.

(4) It is possible to secure fail-safe against disconnection and short circuit of the signal line.

[Brief description of drawings]

FIG. 1 is an interface circuit diagram showing an embodiment of the present invention.

FIG. 2 shows an example of an oscillator circuit in the embodiment.

FIG. 3 shows an example of an AND circuit in the embodiment.

FIG. 4 is a connection diagram when the embodiment is applied to a smoke sensor.

FIG. 5 is a connection diagram when the embodiment is applied to a temperature sensor.

FIG. 6 is a connection diagram when the embodiment is applied to a fire detector.

[Explanation of Codes] 1 ... Detector 2 ... Interface circuit 3 ... Controller 4 ... Interface circuit 5, 6 ... Signal line 7 ... Detector body 8 ... Projector OSC ... Oscillator

Claims (1)

[Claims] 1. An interface circuit for connecting a detector and a controller with a signal line, wherein the interface circuit of the controller applies direct current to the signal line, and changes the on / off voltage of the signal line from the detector. A circuit configuration is provided for extracting the detection signal and a normal coupling state check signal with the detector side, and the interface circuit of the detector drives the signal line on / off by an oscillation signal when there is no detection output from the detector body. At the same time, the circuit configuration is such that DC power is taken in from the controller side through the signal line during the off-driving period of the signal line, and the signal line is turned off when a detection output is generated from the detector body. Interface circuit.