JPS61195491A - Self-fire alarm - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Details 1] The present invention is a self-fire alarm system, more specifically, it has a sensor such as a heat sensor that detects the occurrence of a fire, and responds to the state of the sensor. The present invention relates to a self-fire alarm device in which a load circuit such as an alarm device is driven by a fire alarm device.

[Background Art] Generally, in this type of fire alarm system, a sensor such as a heat detector, or a sensor for detecting the occurrence of a fire is installed in the device. When a short circuit occurs on a live line, a protection circuit is installed that detects the short circuit and generates a short circuit detection signal, and protects the load such as an alarm device from being destroyed by the short circuit current. . This type of protection circuit is often of the current detection type, and when a short circuit current is detected, the output drive circuit is turned off to protect the load by suppressing the amount of current flowing to the load. . In addition, since the output drive element is in the off state, 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 will not be 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 circuit There is a problem that the configuration becomes complicated. Furthermore, since the short-circuit detection signal is maintained by the latch circuit and delay circuit, even if the short-circuit condition is released, the short-circuit detection signal remains unchanged until the latch circuit is re-latched or the delay circuit is delayed. continues to be output, and there is a problem in that it takes time to recover from the short-circuit condition.

[Objective of the Invention 1 The present invention has been made in view of the above-mentioned points, and its main purpose is to provide a self-contained device that has a simple configuration and does not place a burden on the output drive circuit. Another object of the present invention is to provide a fire alarm device that detects a short circuit state or the release of a short circuit state without 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 goodwill 1 via the transmission line 5, and the state of the sensor 3 connected to the terminal device 2 can be monitored by the goodwill 1. A so-called intelligent self-fire alarm system is illustrated in which each terminal device 2 is provided with an alarm device 4, and the status of the sensor 3 can also be checked on the terminal device 2.

Goodwill 1 calls multiple terminals 2 cyclically, and a return signal containing the status of sensor 3 is sent back from the terminal 2 that matches the address specified by Goodwill 1. There is. As shown in FIG. 3, terminal device 2 called by Goodwill 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 the return signal from the terminal device 2. Address signals, 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 includes a multiplex transmission superimposition section 11 that converts the output of the sensor 3 into a time division multiplex transmission signal, and an output drive circuit inserted between the sensor 3 and the multiplex transmission superposition section 11. 12, and a protection circuit 13 that detects a short circuit when a short circuit occurs between terminals TI and T2 to which the sensor 3 is connected. Terminal T is connected to the power supply Vcc.

The multiplex transmission superimposing unit 11 receives a return signal superimposed on the transmission line 5.
This circuit creates a Zener voltage, and is grounded through a Zener diode Z, so that the time division multiplexed transmission signal is superimposed on the Zener voltage, as shown in FIG.

The output drive circuit Wi112 includes a first transistor Q1 that is turned on when the terminal device 2 is called, and second and third transistors Q2, Ql, whose bases are connected to the collector of the first transistor Q. a fourth transistor Q whose base is connected to the collector of the third F transistor Q; a diode D1 connected in the forward direction to the collector of the fourth transistor Q; and a plurality of resistors R1 to R.
Consisting of 2. The 7 nodes of the diode D1 are connected to one terminal T2, and the fourth transistor Q4
When the sensor 3 is turned on, the output of the sensor 3 is input to the multiplex transmission superimposition section 11 via the diode D1 and the fourth transistor Q.

Here, the emitter resistance R1 of the second transistor Q2 is set to a value sufficiently smaller than the impedance of the sensor 3 connected between the terminals T and T2.

The protection circuit 13 includes a Zener diode Z2 whose cathode is connected to the seventh node of the diode D1, a fifth transistor Q5 whose base is connected to the seventh node of the Zener diode Z2 via a resistor R6, and a Zener diode Z2. Resistor R8 A current-limiting resistor R, one end of which is connected to which connection point, and the other end of which is grounded, and the first transistor Q.
and the connection point between the collector of and the collector resistor R6 and the fifth transistor Q.

A diode D2 inserted in the forward direction between the collector of
and a diode Ds inserted in the forward direction between the connection point between the collector of the third transistor Q and the collector resistor R6 and the collector of the fifth transistor Q. The cathode of the Zener diode Z2 is also connected to a connection point between the collector of the second transistor Q2 and the collector resistor R4.

(Operation) The operation will be explained below. First, under normal conditions, terminal device 2
When called, the first transistor Q1 is turned on, the second transistor Q2 and the third transistor Q are turned off, and the fourth transistor Q4 is turned on. Therefore, the Zener voltage Vz is applied to the multiplex transmission superimposing section 11 during the scan time period.

At this time, the output of the sensor 3 passes through the fourth transistor Q 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 scanning time period, the first transistor Q1 is in the off state, so the second transistor Q2 is in the on state.
The fourth transistor Q4 is turned off, and the output of the sensor 3 is not input to the multiplex transmission superimposition section 11. Here, since the emitter resistance R3 of the second transistor Q2 is set to be sufficiently small compared to the impedance of the sensor 3, the voltage between the terminals TI and T2 is 10 V from the power supply voltage.
It is approximately equal to cc.

If terminals T and 72 are short-circuited, the Zener diode Z
2 exceeds the breakover voltage of the Zener diode Z2, the terminal voltage of the current limiting resistor R1 rises, and the fifth
The transistor Q is turned on. Therefore, the collector voltage of this fifth transistor Q can be taken out as a short circuit detection signal. Diodes D2, D are connected to the collector of the fifth transistor Q5, and these diodes D2, D are connected to the bases of the second and fourth transistors Q, , Q, respectively. Fifth transistor Q.

When Q is turned on, the second and fourth transistors Q
2, Q4 is turned off, and the operation of the multiplex transmission/superposition unit 11 is stopped. Here, while the terminals T1 and T12 are short-circuited, the fifth transistor Q is kept in the on state or the short-circuit detection signal continues to be output.
The operation of the multiplex transmission superimposing unit 11 is also maintained in a stopped state.

As soon as the short-circuit condition is released, the fifth transistor Q5 is turned off, and the operation of the terminal device 2 is interrupted.

[Effect of the invention 1] As described above, the present invention includes a sensor for detecting the occurrence of a fire, a load circuit such as an alarm device that is activated in response to the state of the sensor, and a combination of the sensor and the load circuit. An output drive circuit is inserted between the sensor and the load circuit to turn on and off the connection between the sensor and the load circuit, and the output drive circuit is inserted between the sensor and the load circuit to shut out short circuits and short circuits. It consists of a protection circuit that outputs a detection signal and turns off the output drive circuit.The protection circuit consists of a Zener diode connected in series with a current limiting resistor to the sensor and the series circuit inserted into the power supply, and a Zener diode that outputs a detection signal and turns off the output drive circuit. It is composed of a switch element that turns on according to the terminal voltage of the current limiting resistor and turns off the output drive circuit when there is a short circuit between the connected terminals, so the short circuit state or short circuit state is released. This has the advantage of being able to detect the occurrence of a problem without any time lag, and has the advantage of being simple in structure and not placing any burden on the output drive circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a time division multiplex transmission apparatus using the same, 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, D2, D are diodes, R
, are resistors, Q is a transistor, and Z2 is a Zener diode. Agent Patent Attorney Ishi 1) Chief 7 Figure 2 Figure 3

Claims (1)

[Claims] (1) A sensor that detects the occurrence of a fire, etc., and a load circuit such as an alarm device that is activated in response to the state of the sensor,
An output drive circuit is inserted between the sensor and the load circuit, and controls the connection between the sensor and the load circuit on and off.If there is a short circuit between the terminals to which the sensor is connected, the output drive circuit detects the short circuit and issues a short circuit detection signal. The protection circuit consists of a Zener diode that is connected in series with the sensor along with a current limiting resistor, and the series circuit is inserted into the power supply. A self-fire alarm device comprising a switch element that turns on according to the terminal voltage of a current limiting resistor and turns an output drive circuit off when a short circuit occurs between the terminals.