JPS5947360B2 - Dimming fire detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dimming type fire detector, and more particularly to a fire detector that does not issue false alarms due to dew condensation, fog, or the like.

Conventional dimming type fire detectors have a light emitter and a light receiver installed at both ends of the light path, detect a decrease in the amount of light received by the light receiver due to smoke entering the light path, and detect the decrease in the electrical output of the light receiver. It is configured to send out a fire detection signal when the temperature falls below a certain value.

However, the amount of light received by the light receiver is not only reduced by smoke, but also by condensation on the surface of the light emitter or light receiver due to sudden changes in temperature.

Furthermore, when a fire detector is installed in a tunnel, the amount of light received may decrease due to the occurrence of fog. Therefore, conventional dimming type fire detectors have the disadvantage that they may erroneously issue a fire detection signal due to condensation or fog even though there is no smoke. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional drawbacks and to provide a dimming type fire detector that does not issue false alarms due to condensation or fog.

The sensor of the present invention is characterized in that it is provided with a dew condensation sensor and configured so that a smoke detection signal is not output based on the moisture detection signal of the dew condensation sensor.

In addition, the smoke detection signal and the moisture detection signal are input to an AND circuit, and the output of the AND circuit blocks the fire detection signal or displays dew condensation, thereby achieving the above purpose and ensuring that fog It is possible to identify the type of circuit, and there are also advantages such as common use of circuits.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

That is, the light emitted from the light projecting element LED is received by the light receiving element PD, converted into a voltage, and input into the amplifier A. When the output voltage of amplifier A is above a certain value, transistor Trl
is off. When the amount of light received by the light receiving element PD decreases due to smoke etc. and the output of the amplifier A becomes below a certain value, the transistor T
rl is turned on, and one input of the AND circuit ANDI becomes high level along the path from the power supply + to the emitter of the transistor Trl to the collector thereof. Further, since the other input of this AND circuit receives a high level from the power supply via the resistor R1, the output of the AND circuit AND becomes a high level, triggering the thyristor S1 to conduct. This allows, for example, a distant monitoring device to detect the occurrence of a fire. On the other hand, the dew condensation sensor K is connected to the base of the transistor Tr2, and the power supply is connected through the resistor R2.
Connect to. The collector of transistor Tr2 is resistor R1
The emitter is connected to the power supply ÷ through the power supply ÷, and the emitter is connected to the power supply -. As a result, the transistor Tr2 is normally in an off state, but if condensation occurs due to a sudden change in temperature, etc., the resistance value of the dew condensation sensor K becomes small, the base potential of the transistor Tr2 rises, and the emitter current flows, turning it on. become. As a result, the collector of the transistor Tr2 becomes low level. That is, one input of the AND circuit ANDI is set to low level. Therefore, the transistor T
No smoke detection signal from rl is provided to the gate of thyristor S1. In other words, when the amount of light received by the light receiving element PD decreases due to dew condensation, the fire detection signal is not transmitted based on the moisture detection signal of the dew condensation sensor.
The same applies when the amount of received light is reduced due to fog. As a result, the sensor of this embodiment has the effect of detecting only smoke without generating false alarms due to dew condensation or fog.
Note that when the light emitting element and the light receiving element are installed at separate locations, it is desirable to provide each with a dew condensation sensor.
FIG. 2 shows a second embodiment of the invention.

In this case, the circuit related to smoke detection is the same as in the first embodiment, but the configurations of the dew condensation sensor and logic circuit are different. That is, the resistor R3 is connected to the power supply +, the dew condensation sensor K is connected to the power supply -, and the connection point between the resistor R3 and the dew condensation sensor K is connected to the base of the transistor Tr2. Transistor Tr
The emitter of No. 2 is connected to the power supply +, and the collector is connected to the power supply - through a resistor R4. The collector of the transistor Tr2 is connected to one input of the AND circuit AND2, and the collector of the transistor Tr is connected to the other input. Then, the output of the AND circuit AND2 is connected to the gate of the thyristor S2, and the anode of the thyristor S2 is connected to the power supply +.
The cathode is connected to the power supply through a parallel circuit of a resistor and relay RL.
Connect to. The power supply + is connected to the anode of the thyristor S3 via the break contact rl of the relay RL, and the cathode thereof is connected to the power supply -. The collector of the transistor Trl is connected to the gate of the thyristor S3. In this case, moisture is detected by the condensation sensor, and
When dimming is detected by the smoke detector, the output of the AND circuit AND2 operates the relay RL, inhibiting the operation of the thyristor S3. That is, if the fire is definitely caused by fog or dew condensation, it is possible to prevent the fire detection signal from being sent. Further, fogging can also be removed by energizing the built-in heater through a contact (not shown) of the relay RL. In the case of dimming due to smoke, the resistance of the dew condensation sensor K is large, so... Transistor Tr2 is off,
AND circuit AND2 does not output an output, and relay RL does not operate. Therefore, as usual, the transistor Trl is turned on due to a decrease in the output voltage of the light receiving element PD, and the thyristor S3 is driven to conduct and self-maintain. This allows fire detection signals to be sent to remote locations. Incidentally, as shown in FIG. 3, if an indicator lamp L or the like is connected in place of or together with the relay RL shown in FIG. 2, it is possible to display the occurrence of fog.

In this case, the indicator lamp lights up at the same time as the fire alarm, so it can be recognized that it is caused by fog or dew condensation. Of course, in the case of operation due to smoke, the indicator lamp L does not light up. In this case, the part related to the indicator lamp etc. may be provided, for example, on the receiver side and used in common for a plurality of similar fire detectors. In this case, one indicator lamp etc. is sufficient for multiple fire detectors. Furthermore, instead of the indicator lamp, for example, a fog lamp may be turned on. If installed in a tunnel or the like, fog lights can be turned on automatically when fog occurs, which is extremely beneficial. As described above, in the present invention, a light reduction detector and a dew condensation sensor are provided, and the fire detection signal etc. are controlled according to the combination of the output signals of both. Therefore, it is possible to provide a stable and reliable fire detector that does not issue false alarms.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing different embodiments. In the figure, LED...light emitting element, PD...light receiving element, A...amplifier, Trl, Tr3...transistor, R1 to R4...resistance, K...dew condensation sensor, . A
NDl, AND2...AND circuit, S1-S3...
Thyristor, RL...Relay, L...Indication lamp.

Claims (1)

[Scope of Claims] 1. A dimming device comprising a light emitting element and a light receiving element disposed at both ends of an optical path, and a dimming detector that outputs a smoke detection signal when the electrical output of the light receiving element falls below a certain value. 1. A dimming type fire detector, characterized in that a dew condensation sensor is provided, and the detection signal is not outputted or the dew condensation is displayed depending on the moisture detection signal of the dew condensation sensor. 2. In the attenuation type fire detector according to claim 1, an AND circuit that inputs the smoke detection signal and the moisture detection signal, and a fire detection signal that is activated and self-maintained by the smoke detection signal. The apparatus is characterized by comprising: a sending means; and a cutoff means operated by the output of the AND circuit to cut off the sending circuit or self-holding circuit of the fire detection signal sending means. 3. The dimming type fire detector according to claim 1 includes an AND circuit into which the smoke detection signal and the moisture detection signal are input, and a display circuit activated by the output of the AND circuit. characterized by.