JPH0575155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a malfunction prevention circuit for a disconnection monitoring device used in disaster prevention equipment such as fire alarm equipment and theft prevention equipment.

[Background Art] As a disconnection monitoring device for monitoring disconnections in fire alarm equipment, etc., it is conceivable to provide a termination capacitor at the ends of a pair of electrical circuits.

This disconnection monitoring device monitors disconnection based on the charging voltage of the termination capacitor. Therefore, when the power is turned on, the charging voltage of the termination capacitor is unstable, which may cause the disconnection monitoring device to malfunction.

In addition, when a fire detector, etc. is activated, the fire detector, etc. becomes short-circuited, so the termination capacitor is discharged, and the voltage across the termination capacitor decreases, and in this case, the disconnection monitoring device also detects malfunction. It can happen.

Further, even when restoring an activated fire detector or the like, the disconnection monitoring device may malfunction until the termination capacitor is completely charged.

[Object of the Invention] The present invention has been made by focusing on the problems of the above-mentioned background art, and is intended to reliably prevent malfunctions when power is turned on, when a fire detector, etc. is activated, and when a fire detector, etc. is restored. The object of the present invention is to provide a malfunction prevention circuit for a disconnection monitoring device for disaster prevention equipment.

[Embodiment of the Invention] FIG. 1 is a circuit diagram showing an embodiment of the present invention.

The embodiment shown in FIG. 1 is an embodiment of fire alarm equipment, including a repeater connected to a receiver (not shown), a terminator T including a terminating capacitor CE, and an electric line connecting the repeater and the terminator T. and multiple fire detectors DE installed on the electrical circuit.

First, the terminator T has a resistor R1 with a relatively large resistance value and a termination capacitor CE connected in series.
Resistor R2 and diode D1 with relatively small resistance value
A series circuit with is connected in parallel with the resistor R1. In other words, the time constant is set so that the charging time to the termination capacitor CE is relatively long and the discharging time is relatively short.

Furthermore, a Zener diode connected in parallel to the series circuit of the resistor R1 and the termination capacitor CE is used to prevent destruction of the capacitor CE when the termination T is connected with reverse polarity. The Zener diode also serves as voltage protection against external noise.

Inside the repeater, there is a constant voltage circuit 10 that converts the power supply (for example, 24V) supplied from the receiver to a predetermined constant voltage (for example, 10V), an integration circuit 11 that integrates this output voltage, and a voltage output from the integration circuit 11. It has an inverter 12 that inverts the output signal, a monostable multivibrator 13 that receives the output signal of the inverter 12 as a reset signal, and a delay circuit 14 that delays the output signal of the monostable multivibrator 13 for a predetermined period of time.

The output signal of the monostable multivibrator 13 is
It is called a "clear pulse" in the sense that it clears a break detection latch L1, which will be described later, and the output signal of the delay circuit 14 is called a "break detection pulse" in the sense that it is a pulse that causes a break detection operation to be performed.

Further, a positive power source (for example, 24V) and a common terminal C are connected, and a series circuit of a resistor R3, a transistor TR1, and a resistor R4 is connected between the L terminal and the ground. Transistor TR1 is
By turning it on, it supplies power to the fire detector DE and charges the termination capacitor CE, and by turning it off, the power supply to the electric circuit is cut off and the fire detector DE is restored. It is something that makes you Further, the base voltage of the transistor TR1 increases when the fire detector is activated, and the base voltage is used for fire detection.

Furthermore, a resistor R is connected between the positive power supply and ground.
5, a transistor TR3, a resistor R6, and a Zener diode ZD2 are connected in series, and a connection point between the transistor TR3 and the resistor R6 is connected to the L terminal. The Zener voltage of the Zener diode ZD2 is, for example, 9V. transistor
TR3 forms a discharge loop for the termination capacitor CE by turning it on, and at this time,
Anode of Zener diode ZD2 (point P1)
A disconnection detection signal is generated at the same time.

Also, a resistor R is connected between the positive power supply and the ground.
7, R8, and the transistor TR4 are connected, and the connection point between the resistors R7 and R8 is connected to the base of the transistor TR3.

Furthermore, a Zener diode ZD1 is connected to the base of the transistor TR1. This Zener diode ZD1 constitutes a constant current circuit together with the transistor TR1, and the transistor TR
The upper limit of the load current (the current flowing through the electric circuit, that is, the fire detector DE) is regulated.

Furthermore, a series circuit for generating a reference voltage is connected between the output terminal of the constant voltage circuit 10 and the ground, and is composed of resistors R9, R10, R11, and R12, and each connection point is connected in descending order of voltage. , P2, P3,
Let it be P4.

The disconnection detection comparator 20 that detects disconnection is
The disconnection detection signal (voltage of P1) is set to the reference voltage (P
2 (for example, 6V), and when the disconnection detection signal is higher than the voltage at point P2,
It is determined that the electric path connected between the C and L terminals is disconnected.

On the other hand, a comparator 21 for inhibiting disconnection detection at the time of a fire alarm compares the base voltage of the transistor TR1 with a reference voltage (the voltage at point P3, for example, 4V), and Due to the occurrence of a fire, the voltage at point P
When the voltage exceeds the reference voltage No. 3, the disconnection detection operation is prohibited.

The comparator 22 that detects the disconnection detection operation at the time of recovery compares the output voltage of the disconnection detection comparator 20 divided by resistors R13 and R14 with a reference voltage (the voltage at point P4, for example, 2V), When the divided voltage of the output voltage of the disconnection detection comparator 20 becomes equal to or higher than the reference voltage at point P4, it is determined that it is time to recover, and the disconnection detection operation is prohibited. Note that the resistance value of the resistor R14 is relatively large, and a capacitor C1 is connected in parallel with the resistor R14.
is connected. Resistor R14 is capacitor C
This increases the discharge time constant of 1.

In addition, a fire comparator 30 that detects fire
compares the base voltage of transistor TR1 with a reference voltage (the voltage at point P3, for example 4V), and determines that there is a fire when the base voltage of transistor TR1 exceeds the reference voltage at point P3. It is something.

The break test latch L1 that holds the output signal of the break test comparator 20 outputs "L" when the electrical circuit is not broken, that is, normal, and outputs "H" when the circuit is broken. .

AND1 is used to set the break test latch L1 when there is a wire break and a break test pulse is generated. AND2 is for resetting the break test latch L1 when a clear pulse is generated in a steady state. AND3 outputs an "H" signal when an interruption detection pulse occurs in a steady state.

NOR1 prohibits disconnection alarm when the fire detector is restored, and normally outputs "H". When NOR2 receives a recovery pulse from a receiver (not shown) or when AND3 outputs an H signal due to a disconnection pulse,
The transistor TR1 is turned off to ensure the recovery operation and disconnection detection operation of the activated fire detector. In addition to this, OR1 and OR2 are provided.

Next, the operation of the above embodiment will be explained.

First, when the positive power supply is turned on, the constant voltage circuit 10 is activated and its output voltage gradually increases. During this time, the output voltage of the integrating circuit 11 also gradually increases, and the inverter 12 outputs "H" until the output voltage of the integrating circuit 11 reaches a predetermined value.
Since the monostable multivibrator 13 is held in the reset state, it does not generate a clear pulse, and the delay circuit 14 does not generate a break detection pulse.

As a result, AND3 does not open and no recovery pulse is input, so NOR2 outputs "H",
Transistor TR1 turns on, terminating capacitor CE
starts charging and becomes fully charged.

Note that the charging voltage of the terminating capacitor CE is, if the circuit resistance of the pair of circuits is ignored, the sensor DE is
In the case of constant temperature or differential type sensors that have mechanical electrical contacts and do not consume current during monitoring, they are charged to 24V, the same as the voltage between C and L.
In addition, if the sensor DE has a semiconductor circuit such as an ionization type or photoelectric type, and a small monitoring current flows during monitoring, up to 22V, for example, which is determined by the number of connected sensors and their combined impedance. It will be charged.

Further, while the inverter 12 is generating an "H" output, the break test latch L1 and the fire latch L2 are also reset.

On the other hand, when the output voltage of the constant voltage circuit 10 reaches the constant voltage, the inverter 12 sets the output voltage to "L", so the monostable multivibrator 1
3. The reset for the disconnection latch L1 and the fire latch L2 is released.

Here, when the disconnection monitoring signal is input, the monostable multivibrator 13 generates a clear pulse. The disconnection monitoring signal is output by a receiving circuit (not shown) of the repeater when, for example, an address received from a receiver (not shown) matches an address of the repeater itself.

When the monostable multivibrator 13 generates a clear pulse, normally NOR1 outputs "H" due to the "L" output of the disconnection prohibition comparators 21 and 22, so via AND2 and OR1, The break test latch L1 is cleared.

Then, after a predetermined time delay from the generation of the clear pulse, the delay circuit 14 generates a disconnection pulse (see FIG. 2).

Also, since NOR1 normally outputs "H",
The disconnection pulse opens AND3, the disconnection pulse is applied to the base of the transistor TR4, the transistor TR4 is turned on, and the transistor TR3 is turned on.

On the other hand, at this time, the output of NOR2 becomes "L" due to the disconnection pulse passed through AND3, and transistor TR1 is turned off.

By turning off this transistor TR1, C, L
Power supply to the electrical path between the terminals is cut off, and transistor TR3 is turned on, forming a discharge loop of termination capacitor CE by resistors R2 and R5 and transistor TR3.

As a result, the termination capacitor CE is connected to the resistor R2,
Diode D1, resistor R5 and transistor TR3
Since it discharges through the C and L terminals, 22V
A voltage is generated before and after, so at point P1,
As shown in Figure 2 1, from a power supply voltage of 24V, C,
A voltage of approximately 2V or less is generated after subtracting the voltage between the L terminals. Here, for example, a voltage of 6V is generated at point P2, where the output voltage of 10V from the constant voltage circuit is divided, and the voltage at point P1 is lower than that, so the output of the fault detection comparator 20 is " It remains at "L". For this reason, the output of AND1 is also “L”.
As it is, the break test latch L1 cannot be set, and its Q output terminal becomes "L" indicating that there is no break.
signal is generated.

Note that when the termination capacitor CE is discharged through the transistor TR3, the transistor TR
3 functions as a constant current circuit by the action of resistors R5, R7 and R8, so the termination capacitor CE
Discharging is performed at a constant current regardless of the charging voltage level depending on the number or type of sensors DE connected.

On the other hand, if the electric path is disconnected, the following operation is performed.

In other words, as shown in Fig. 2, when a break detection pulse is generated, transistor TR1 is turned off, transistor TR4 is turned on, and transistor TR3 is turned on, the electrical circuit is broken and the termination capacitor CE is turned on. It is not discharged, and the voltage across the termination capacitor CE is not applied between the C and L terminals. Therefore, the voltage at point P1 increases to approximately 9V, which is the Zener voltage of Zener diode ZD2.
For this reason, the output of the break test comparator 20 becomes "H", and while AND3 outputs the break test pulse, AND1 outputs "H", setting the break test latch L1. As a result, its Q output becomes "H", indicating a disconnection. Furthermore, even when the power supply voltage fluctuates, the Zener diode ZD2
This serves to ensure that the voltage at point P1 is higher than the voltage at point P2 when the electrical path between the CL terminals is disconnected.

Next, the fire detection operation will be explained.

When a fire occurs, the fire detector CE becomes short-circuited, as shown in FIG. 2, and a large current flows through the fire detector DE, resistor R3, transistor TR1, and resistor R4. For this reason, the voltage drop across the resistor R4 increases, and the emitter voltage of the transistor TR1 changes from the voltage (for example, 24V) applied between the terminal C and the ground to the resistor R4.
It attempts to rise to a voltage close to the voltage divided by the resistance between R3 and R4. By the way, the base potential of transistor TR1 is its base-emitter voltage (V _BE )
Since it is the voltage obtained by adding the voltage drop of resistor R4 to
As the voltage drop across resistor R4 increases due to the operation of fire detector DE, its base potential also decreases between resistors R3 and R.
The voltage will rise to the voltage divided by 4. However, if the base potential of transistor TR1 is the Zener voltage of Zener diode ZD1 (for example
5.6V), the Zener diode ZD1
conducts, and the base potential stops rising. Its base potential is applied to the non-inverting input terminal of the fire comparator 30.

On the other hand, the voltage at point P3 is applied to the inverting input terminal of the comparator 30, which is about 4V. Therefore, when the base potential of transistor TR1 rises above the voltage at point P3, fire comparator 30 outputs "H" and fire latch L2 is set. At this time, an "H" signal is output to the inverted output terminal of the fire latch L2, and this signal becomes a fire signal.

Note that the base potential of the transistor TR1 stops increasing when it reaches the Zener voltage (for example, 5.6 V) of the Zener diode ZD1. From now on, transistor TR1 and Zener diode ZD
1 operates as a constant current circuit and limits the current flowing through the activated fire detector DE to a predetermined value.

Next, a description will be given of an operation for preventing malfunctions in wire breakage detection.

Since a malfunction may occur in wire breakage detection, timings at which wire breakage detection should not be performed include when the power is turned on, when a fire alarm is issued, and when the fire detector DE is restored.

First, we will explain what happens when the power is turned on.

The disconnection test comparator 20 has the voltage at point P1 and
Compare the voltage at point P2, which is the reference voltage, and
When the voltage is high, it is determined that the wire is disconnected. However, when the power is turned on, the output voltage of the constant voltage circuit 10 is not high enough, so the voltage at point P2 is low, and there is a possibility that it may be mistaken for a wire breakage even if it is not a wire breakage.

When the power is turned on, the output voltage of the constant voltage circuit 10 gradually increases, but the output voltage is integrated by the integrator circuit 11, the output voltage of the integrator circuit 11 is inverted by the inverter 12, and this inverted signal becomes monostable. It serves as a reset signal for the multi-vibrator 13, the break test latch L1, and the fire latch L2. Therefore, the reset signal is output from the inverter 12 until the output voltage of the constant voltage circuit 10 becomes sufficiently high, and during this period, even if a disconnection monitoring signal is input from a receiving circuit (not shown), the monostable multivibrator 13 is cleared. Does not generate pulses. For this,
Since no disconnection detection pulse is generated from the delay circuit 14 when the power is turned on, disconnection detection is not performed and erroneous operation of disconnection detection does not occur when the power is turned on.

Also, the reset signal of inverter 12 is OR2
and OR1 to the reset terminals of the disconnection latch L1 and the fire latch L2, and the latches L1 and L
Set the output of 2 to "L".

Next, prevention of malfunction of disconnection detection when a fire is reported will be explained.

When a fire is reported, the fire detector DE is short-circuited as shown in FIG. The disconnection detection latch L1 will output a disconnection signal. If this continues, disconnection detection will malfunction when a fire is reported.

However, in the above case, as the C and L terminals are shorted, a large current flows through the resistor R4, the collector potential of the transistor TR1 becomes high, and its base potential also becomes higher than the voltage at the point P3. , the detection failure comparator 21 outputs "H" as shown in FIG. 2 and NOR1 goes "L" when the alarm is issued.
, AND3 is held in the "L" output state.
Therefore, AND1 closes and the disconnection latch L1
is not set, and no disconnection signal is erroneously output.

Next, we will explain how to prevent malfunction of disconnection detection when the fire detector DE is restored.

At the time of recovery, as shown in FIG. 2, when a recovery pulse is input from the recovery circuit (not shown) of the repeater in response to a recovery command from the receiver (not shown),
Since NOR2 outputs "L", the transistor
Since TR1 is turned off and power is no longer supplied to the fire detector DE, the self-holding circuit of the fire detector DE is released. The recovery pulse also resets the break test latch L1 and the fire latch L2.

On the other hand, since the electric path between the C and L terminals is not broken, a voltage corresponding to the Zener voltage of the Zener diode ZD2 is generated at the point P1, and the break detection comparator 20 generates an "H" output. This "H"
The capacitor C1 is charged by the output while the recovery pulse is input, and the voltage at point P5 becomes higher than the voltage at point P4, and the comparator 22, which prohibits failure during recovery, generates an "H" output, and the output of NOR1. Set to "L".

Then, after the restoration operation is completed, when the transistor TR1 is turned on, charging of the termination capacitor CE is started. During this charging, the voltage at point P1 may not become lower than the voltage at point P2, and the break detection comparator 20 may output "H". If this continues, a disconnection signal will be erroneously generated.

However, in the above case, the voltage at the non-inverting input terminal of the comparator 22 for inhibiting disconnection during recovery is higher than point P4 for a predetermined period of time, so NOR1 outputs "L", AND3 is closed, and AND1 is also closed. Therefore, the above-mentioned malfunction is prevented.

Note that since the resistance value of the resistor R14 is relatively large, the electric charge charged in the capacitor C1 is gradually discharged over a predetermined period of time. As shown in
(the time required for the voltage at point P1 to become equal to or lower than the voltage at point P2), it outputs an "H" signal. When the predetermined period of time has elapsed, the comparator 22 for inhibiting disconnection during recovery generates an "L" output, and the NOR
1 outputs "H" which is the normal state, but when this normal state is reached, the termination capacitor CE is sufficiently charged.

2. FIGS. 1, 2, 3, and 4 are time charts showing each operation of the above embodiment.

The above embodiment includes a reset means, a disconnection detection pulse output prohibition means, and a disconnection signal output prohibition means.

The reset means resets the disconnection detection latch L1, which outputs and holds the disconnection signal in response to the output of the disconnection detection signal from the disconnection detection comparator 20, to the power supply circuit 10 when the power is turned on.
This is a means of resetting until the output voltage becomes stable. Specifically, it is composed of an integrating circuit 11 and an inverter 12 whose output is inverted when the output of the integrating circuit 11 reaches a predetermined value.
Other circuits may also be used. Furthermore, instead of the disconnection detection latch L1, a disconnection signal output circuit such as a switching circuit having a self-holding function may be used.

The means for inhibiting the output of the failure detection pulse is to suppress the output of transistors TR1, TR3, and
This is a means for prohibiting the output of a disconnection detection pulse that causes the disconnection detection circuit constituted by the disconnection detection comparator 20 to perform a disconnection monitoring operation. Specifically, the transistor TR1 and the comparator 21 that prohibits disconnection when an alarm is issued.
However, other circuits may be used.

The disconnection signal output inhibiting means is a means for prohibiting the disconnection detection latch L1, that is, the disconnection signal output circuit, from being set when the sensor DE is restored.

Specifically, the output of the disconnection detection comparator 20 of the disconnection determination circuit is integrated, and the charging resistor R13 is
an integrator circuit consisting of a capacitor C1 and a discharging resistor R14, a comparator 22 that outputs an output when the charging voltage of this integrator circuit exceeds a predetermined value, and an output of this comparator 22. Prohibiting the output of the comparator 20 from being input to the reset terminal of the disconnection signal output circuit L1,
In addition, there is a gate circuit consisting of NOR1, AND3, AND1, and OR1, which passes the input recovery pulse to the reset terminal of the disconnection signal output circuit L1.
2, but other configurations may be adopted.

In addition, in the above embodiment, the discharge transistor
TR3 and resistor R5 constitute a circuit that forms a discharge loop for the termination capacitor CE.

In addition, in the above embodiment, the break test comparator 2
0, a constant voltage circuit 10 that converts a power supply voltage (for example, 24 V) supplied from a constant voltage power supply unit to a predetermined voltage (for example, 10 V) for generating a reference voltage, and a resistor that divides the output voltage of the constant voltage circuit 10. R9, R1
0 is a disconnection monitoring circuit.

Further, in the above embodiment, the disconnection detection latch L1 is a disconnection signal output circuit.

In the above embodiment, the disconnection monitoring device and its malfunction prevention circuit are provided in the repeater, but they may also be provided in the receiver, and can also be used in anti-theft equipment. In addition, monostable multivibrator 13
Instead, a timer or the like that generates an output at predetermined time intervals can also be used.

[Effects of the Invention] The malfunction prevention circuit of the disconnection monitoring device for disaster prevention equipment of the present invention reliably prevents malfunction of disconnection detection when power is turned on, when a fire detector, etc. is activated, and when a fire detector, etc. is restored. It has the effect of being able to.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. 2. FIGS. 1, 2, 3, and 4 are time charts showing operations in the above embodiment. 10...constant voltage circuit, 11...integrator circuit, 13
... Monostable multivibrator, 14 ... Delay circuit, 20 ... Comparator for failure detection, 21 ... Comparator for prohibiting failure detection at the time of alarm, 22 ... Comparator for prohibiting failure detection at the time of recovery, 30 ... Comparator for fire,
CE... Terminating capacitor, L1... Break test latch,
L2...Fire latch.

Claims (1)

[Scope of Claims] 1. A terminating capacitor connected to the ends of a pair of electrical circuits to which an abnormality detector such as a fire detector is connected; A terminating capacitor that is provided at the base end of the pair of electrical circuits and is normally in an off state. , a discharge transistor that turns on when a disconnection detection pulse is input and forms a discharge loop of the termination capacitor via the pair of electric circuits; and a voltage change on the proximal end side of the pair of electric circuits when the discharge loop is formed. a disconnection determination circuit that detects a disconnection in the pair of electrical circuits; a disconnection signal output circuit that outputs a disconnection signal based on the disconnection determination output of the disconnection determination circuit; and a disconnection signal output circuit that outputs a disconnection signal based on the disconnection determination output of the disconnection determination circuit; a reset means for prohibiting the operation of the disconnection signal output circuit until the output voltage of the power supply circuit that supplies the disconnection signal is stabilized; and causing the disconnection determination circuit to monitor disconnection while the abnormality detector is operating. Disconnection detection pulse output prohibition means for prohibiting the output of the disconnection detection pulse; Disconnection signal output prohibition means for prohibiting the disconnection signal output circuit from outputting the disconnection signal when the abnormality detector is restored; A malfunction prevention circuit for a disconnection monitoring device in disaster prevention equipment, characterized by: 2. In claim 1, the reset means is comprised of an integrating circuit that integrates the output voltage of the power supply circuit, and an inverter that inverts the output voltage of the integrating circuit. Malfunction prevention circuit for disconnection monitoring devices in disaster prevention equipment. 3. In claim 1, the disconnection detection pulse output inhibiting means includes a transistor connected in series with the abnormality detector, and when the base potential of this transistor is higher than a reference potential, the disconnection detection pulse output inhibiting means disables the output of the disconnection signal output circuit. What is claimed is: 1. A malfunction prevention circuit for a disconnection monitoring device in disaster prevention equipment, comprising: a comparator for inhibiting disconnection when an alarm is issued, which supplies a reset signal to a reset terminal. 4. In claim 1, the disconnection signal output inhibiting means includes an integrating circuit that integrates the output of the disconnection determining circuit, and a disconnection detection inhibiting comparator that produces an output when the output of the integrating circuit exceeds a predetermined value. and a gate circuit that prohibits the output of the disconnection determination circuit from being input to the set terminal of the disconnection signal output circuit by the output of the disconnection detection prohibition comparator upon recovery, and a gate circuit that allows the recovery pulse to pass. What is claimed is: 1. A malfunction prevention circuit for a disconnection monitoring device in disaster prevention equipment, characterized in that the circuit is configured as follows. 5. The malfunction prevention circuit for a disconnection monitoring device in disaster prevention equipment according to claim 1, wherein the power supply circuit is a constant voltage circuit.