JPH0353679B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a self-fire alarm device, more specifically, it has a sensor such as a heat sensor that detects the occurrence of a fire, and the alarm device responds to the state of the sensor. The present invention relates to a self-fire alarm device in which a load circuit such as the one described above is driven.

[Background Art] Generally, in this type of self-fire alarm device, a sensor such as a heat sensor that detects the occurrence of a fire is connected between both lines of a sensor line consisting of a pair of lines. A predetermined voltage is applied to the sensor line as a line voltage. When the detector detects the occurrence of a fire, it passes current through a predetermined impedance between both lines, outputs a time-division multiplex transmission pulse, and loads alarm information via the detector line. to be transmitted. The load includes a receiver, a repeater, and interlocking processing devices and alarm devices such as fire shutters and sprinklers, and takes measures to deal with fire.

Incidentally, the sensor line is provided with a protection circuit in order to prevent the load from being destroyed by the short-circuit current flowing through the sensor line when the lines of the sensor line are short-circuited. Many of this type of protection circuits are of a current detection type, and when a short circuit current is detected, the output drive is turned off to protect the load by suppressing the amount of current flowing through the load. In addition, since the output drive element is turned off, a latch circuit may be provided to maintain the short circuit detection signal and the short circuit current may be periodically passed to reconfirm the short circuit, or a delay circuit may be provided to maintain the short circuit current for a predetermined period of time. There is a device that outputs a short circuit detection signal by continuing to flow the current.

In these protection circuits, short-circuit current flows periodically or continuously for a predetermined period of time; in any case, short-circuit current flows through the output drive circuit to output a short-circuit detection signal. , it is necessary to design the output drive circuit so that it is not destroyed by short-circuit current, which creates problems such as complicating the circuit configuration and increasing costs.Also, a circuit configuration that maintains the short-circuit detection signal is required, and the overall However, there is a problem that the circuit configuration becomes complicated. Furthermore, since the short circuit detection signal is maintained by a latch circuit or a delay circuit, even if the short circuit condition has been released, the short circuit will continue until the latch circuit is relatched or the delay time of the delay circuit. The problem is that the detection signal continues to be output, and it takes time to recover from the short-circuit condition.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and its main purpose is to have a simple configuration and to avoid placing a burden on the output drive circuit. Another object of the present invention is to provide a self-fire alarm device that detects a short-circuit state or the release of a short-circuit state without a time lag.

[Disclosure of the Invention] (Examples) Examples of the present invention will be described below based on the drawings. In this embodiment, as shown in FIG. 2, a plurality of terminal devices 2 are connected to the master device 1 via the transmission line 5, and the state of the sensor 3 connected to the terminal device 2 can be monitored by the master device 1. At the same time, each terminal device 2 is provided with an alarm device 4, and the state of the sensor 3 is determined by the terminal device 2.
The following is an example of a so-called intelligent self-fire alarm system that can be used to confirm fire alarms.

The master device 1 calls multiple terminal devices 2 cyclically, and a return signal containing the status of the sensor 3 is sent back from the terminal device 2 that matches the address specified by the master device 1. ing. As shown in FIG. 3, the terminal device 2 called by the parent device 1 operates during the period from when it is called until it sends back a return signal as a scanning time period. It receives address signals and control signals, and also sends back a return signal from the terminal device 2. address signal,
Control signals, return signals, etc. are time-division multiplexed transmission signals connected in series in time series.

As shown in FIG. 1, the terminal device 2 has a terminal T ₁ for connecting a sensor line consisting of a pair of lines,
T ₂ is provided, and a sensor 3 is installed between both lines of the sensor line.
is connected. The terminal device 2 also includes a multiplex transmission superimposing section 11 which is part of the load that converts the output of the sensor 3 into a time division multiplexed transmission signal, and a first switch between the sensor 3 and the multiplex transmission superimposing section 11. First as an element
Drive circuit 1 with transistor Q ₁ inserted
2, and a protection circuit 13 that detects a short circuit when a short circuit occurs between the terminals T ₁ and T ₂ (that is, between both lines of the sensor line). Terminal T ₁ (i.e., one line of the sensor line) is connected to one end of the power supply +
Connected to Vc.c. The multiplex transmission superimposition unit 11 is a circuit that creates a return signal to be superimposed on the transmission line ₅ , and is grounded via a Zener diode Z1, and as shown in FIG. It is starting to be superimposed on

The output drive circuit 12 includes a first transistor Q ₁ that is turned on when the terminal device 2 is called;
second and third transistors Q ₂ , _{Q 3} whose bases are connected to the collector of the first transistor Q 1;
Consists of a fourth transistor Q ₄ connected to the collector base of the third transistor Q ₃ , a diode D ₁ connected in the forward direction to the collector of the fourth transistor Q ₄ , and a plurality of resistors R ₁ to R ₇ be done. The anode of diode D ₁ A is one terminal
_T2 , and when the fourth transistor _Q4 is turned on, the output of the sensor 3 is input to the multiplex transmission superimposition unit 11 via the diode _D1 and the fourth transistor _Q4 . It is becoming more and more like this.
Here, the emitter resistance of the second transistor Q _2
R3 is set to a value sufficiently smaller than the impedance of the sensor 3 connected between terminals _T1 and _T2 .

The protection circuit 13 is a Zener diode _Z2 whose cathode is connected to the anode of the diode _D1 .
and a resistor R ₈ at the anode of the Zener diode Z ₂
The base is connected to the second switch element via the second switch element. A fifth transistor _Q5 , a current limiting resistor _R9 whose one end is connected to the connection point between the Zener diode _Z2 and the resistor _R8 and whose other end is grounded, and the collector of the first transistor _Q1 and the collector resistor R A diode D ₂ inserted in the forward direction between the connection point with the third transistor Q ₅ and the collector of the fifth transistor Q ₅ , and a connection point between the collector of the third transistor Q ₃ and the collector resistor R ₆ and the fifth It consists of a diode _D3 inserted in the forward direction between the collector of the transistor _Q5 . The cathode of the Zener diode Z ₂ is also connected to the connection point between the collector of the second transistor Q ₂ and the collector resistor R ₄ .

(Operation) The operation will be explained below. First, under normal conditions, when the terminal device 2 is called, the first transistor
Q ₁ is in the on state, the second transistor Q ₂ and the third transistor Q ₃ are in the off state,
The fourth transistor _Q4 is turned on. Therefore, during the scan period, the multiplex transmission superimposition unit 1
A Zener voltage V _z is applied to . At this time, the output of the sensor 3 passes through the fourth transistor _Q4 and is input to the multiplex transmission superimposition section 11, and a return signal is created. When the terminal device 2 is not called, that is, outside the scan time period, the first transistor _Q1 is off, the second transistor _Q2 is on, and the fourth transistor _Q4 is off. The multiplex transmission superimposing unit 11 includes a sensor 3.
The output of is the one that is not input. Here, the emitter resistance R ₃ of the second transistor Q ₂ is the sensor 3
The voltage between terminals T ₁ and T ₂ is set to be sufficiently small compared to the impedance of the power supply voltage +
It is approximately equal to Vc.c.

When the terminals T ₁ and T ₂ are short-circuited, the voltage across the Zener diode Z ₂ exceeds the breakover voltage of the Zener diode Z ₂ , the terminal voltage of the current limiting resistor R ₉ rises, and the second transistor Q ₅ is turned on. state. Therefore, this fifth transistor Q ₅
The collector voltage can be extracted as a short circuit detection signal. Fifth transistor Q ₅
Diodes D ₂ and D ₃ are connected to the collectors of the transistors Q 2 and D 3 , and these diodes D ₂ and D ₃ are connected to the bases of the second and fourth transistors Q ₂ and Q ₄ , respectively. When transistor _Q5 turns on, the second and fourth transistors
Q ₂ and Q ₄ are turned off, and the multiplex transmission superposition unit 11
operation will stop. Here, terminal T ₁ ,
While _T2 is shorted, the second transistor
Since _Q5 is kept in the on state, the short circuit detection signal continues to be output, and the multiplex transmission superimposing section 11
operation is also kept in a stopped state. When the short-circuit detection signal is output and it is determined that the sensor line is continuously short-circuited, the sensor line is repaired to release the short-circuit state. Immediately after the short-circuit condition is released, the fifth transistor _Q5 is turned off and the operation of the terminal device 2 is restored.

Here, the sensor 3 outputs alarm information by passing a current through a predetermined impedance between both lines or by outputting a pulse using a time division multiplex transmission system. Continuous short circuit conditions on the line can be identified. For example, in the case of a sensor 3 that allows current to flow between both lines of the sensor line through a predetermined impedance, the fifth transistor Q ₅ should be connected to a zener so that the normal current flowing when the sensor 3 is operating does not turn on All you have to do is select the breakover voltage of diode Z ₂ and the value of resistor R ₉ as the current limiting resistor. In addition, in the sensor 3 that transmits alarm information using a time division multiplex transmission method, it is possible to distinguish between a pulse transmission state and a continuous short circuit state, and to check the line voltage of the sensor line. By transmitting pulses in a changed state, a short circuit state and a transmission state can be distinguished.

[Effects of the Invention] Since the present invention has the above-described configuration, it has the advantage of being able to detect a short circuit state or the release of a short circuit state without a time lag, and has a simple configuration. Moreover, it has the advantage that it does not place any burden on the output drive circuit.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a schematic configuration diagram of a time division multiplex transmission apparatus using the same as above, and FIG. 3 is an explanatory diagram of the operation of the same. 3 is a sensor, 11 is a multiplex transmission superimposition unit, 12 is an output drive circuit, 13 is a protection circuit, D ₂ and D ₃ are diodes, R ₉ is a resistor, Q ₅ is a transistor, and Z ₂ is a Zener diode.

Claims (1)

[Claims] 1. A sensor connected between both lines of a sensor line consisting of a pair of lines, which outputs alarm information to the sensor line when it detects the occurrence of a fire, and a sensor connected to the sensor via the sensor line and outputs alarm information to the sensor line. an output drive circuit comprising a load driven according to the load, a first switch element inserted between one line of the sensor line and the load, and an output drive circuit that generates a short circuit detection signal when there is a short circuit between the lines of the sensor line. and a protection circuit that outputs the output and turns off the first switch element, one end of the power supply is connected to the other line of the sensor line, and the protection circuit connects the one line of the sensor line and the power supply. When the series circuit of the current limiting resistor and Zener diode connected between the other end and both lines of the sensor line are short-circuited and the Zener diode becomes conductive, it turns on according to the terminal voltage of the current limiting resistor. and a second switch element, the second switch element being connected to a control terminal of the first switch element so as to turn the first switch element off when it is turned on. Fire alarm device.