JPS5832439B2 - Dimming type separate fire detector - Google Patents

Description

[Detailed description of the invention] The present invention separates a light emitting part and a light receiving part and arranges them facing each other, synchronizes the light emitting part and the light receiving part to detect a decrease in the amount of transmitted light due to smoke, and sends out an alarm signal. Regarding dimming type separate fire detector.

When trying to measure smoke density and transmittance in a space, the light from a light emitting part with a light source is detected by a light receiving part, and the transmittance or attenuation rate of light between the light emitting part and the light receiving part is determined. However, in addition to the light from the light source of the light emitting part, modulated light from fluorescent lamps and other sources enters the light receiving part as disturbance light, and unless this is removed, accurate transmittance or light attenuation cannot be measured. It has been known.

Conventionally, as a means to solve this problem, there have been two methods: (1) modulating the light emitted from the light emitting part with a mechanical chopper or the like and demodulating it in the light receiving part; (2) driving the light source of the issuing part at, for example, IKHz, and then driving the light source at IKHz in the light receiving part; The second method is to process the received light signal through a filter, ① The light of the light emitting part is driven intermittently at a modulation frequency, while a signal synchronized with the intermittent pulse is sent to the light receiving part, and the light receiving part is driven with the intermittent pulse. There is a third method of processing only the light reception signals synchronized with the .

However, the first method has mechanical elements, so
It has drawbacks such as being expensive and having a short lifespan.

Furthermore, the second method generally has a drawback that the high frequency component of the disturbance light may be included within the pass band of the filter, and the S/N of the light reception signal with respect to the disturbance light is poor.

On the other hand, in the third method, compared to the second method, the modulation hole is output intermittently, and the light receiving section receives the light in synchronization with the modulated light. It has a good S/N ratio and is generally widely used.

However, when this is used in a fire detector etc., the power for the light emitting part and the light receiving part is supplied from the fire alarm receiver.
Since a signal line for transmitting and receiving the intermittent pulses between the light emitting part and the light receiving part is required separately, there is a problem in installation work.

That is, since separate fire detectors are installed in warehouses and the like, and the distance between the light emitting part and the light receiving part ranges from several meters to as much as 100 meters, an increase in the number of lines becomes a major problem.

The present invention was made to solve the problem in the third method, and detects fluctuations in the supply current from the light receiving section to the light emitting section due to intermittent light emission, and generates a corresponding control signal. By switching the light receiving signal based on the control signal, there is no need for a special signal line for transmitting and receiving intermittent pulses between the light emitting part and the light receiving part, and the light receiving signal can be generated in synchronization with the intermittent light emission of the light emitting part. The purpose of this invention is to provide a reduced-light separation type fire impression video that can be processed.

The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, the dimming type separate fire detector of the present invention has a light emitting section having a light source 1 and a light source 1 drive circuit 2, a photoelectric conversion circuit 4, an amplifier circuit 5, a filter circuit 6, and a signal processing circuit 7. and a light receiving section equipped with a current change detection circuit 8, a control signal generation circuit 9, and a switching circuit 10, both of which are installed separately via an optical means 3 such as a lens, and are connected to a power supply line i1. It is connected by ii.

The light source 1 is composed of, for example, a light emitting diode, and is turned on by a light source drive circuit 2.

Although a light bulb or the like may be used as the light source 1, a light emitting diode is suitable from the viewpoint of response characteristics.

The light source drive circuit 2 causes the light source 1 to emit light intermittently and intermittently at a specific frequency, and is connected to a power supply line 11 and is supplied with power from the light receiving unit side via the line 11.

The photoelectric conversion circuit 4 is composed of a Si photodiode or the like, and functions to convert the optical signal from the light source 1 into an electrical signal.

The amplifier circuit 5 receives an optical signal (hereinafter referred to as a received light signal) that is converted into an electrical signal by the photoelectric conversion circuit 4.

) to amplify. The filter circuit 6 functions to remove noise by passing only signals of a specific frequency from the amplified received light signal.

Further, the signal processing circuit 7 compares the received light signal with a reference value,
This circuit generates an alarm signal when the received light signal is below a predetermined level.

These are similar to those used in conventional transmittance measurement devices.

The current change detection circuit 8 is provided on the light receiving section side, and for example,
A resistor 8a inserted in series with the power supply line 11 to the light emitting part,
It is composed of a transistor 8b with the resistor 8a connected between the base and emitter, and a resistor 8c connected to the collector of the transistor 8b, and changes the current supplied to the light emitting part flowing through the power supply line 11 as the light source 1 emits light. To detect.

Note that the current change detection circuit 8 is not limited to the above-mentioned configuration, and can also be configured using an operational amplifier or the like.

The control signal generation circuit 9 is composed of, for example, a retriggerable monostable multi-bibreak, and detects the envelope accompanying the intermittent light emission of the light source 1 from the change in the terminal current detected by the current change detection circuit 8, A control signal corresponding to this is output.

The switching circuit 10 is inserted between the filter circuit 6 and the signal processing circuit 7, and switches the received light signal in response to a control signal from the control signal generation circuit 9.

Switching is performed by the current change detection circuit 8 and the control signal generation circuit 9 by closing the switch while the light source 1 is intermittently emitting light and opening it while the light source 1 is not emitting light.

Note that the switching circuit 10 is not limited to the above-mentioned position, but can be inserted at other positions as long as it can switch the light reception signal input to the signal processing circuit 7.

Next, FIGS. 2A, B, and C explain the operation of the present invention.
shows the operating state of the sensor of the above embodiment, and the first
The voltage and current waveforms at the points with the same symbols shown in the block diagram of the figure are shown.

It should be noted that changes at points A, B, and C indicate changes that occurred in temporal correspondence with each other.

Now, when a pulse group as shown in FIG. 2A is intermittently supplied from the light source drive circuit 2 to the light source 1, the light source 1 intermittently emits pulsed light corresponding to the pulses.

On the other hand, since a drive current flows through the resistor 8a of the current change detection circuit 8 as the light source 1 emits light, a voltage drop as shown in FIG. 1B occurs.

Along with this, the transistor 8b turns on, causing a voltage change in the resistor 8C due to the collector current.

Next, in the control signal generation circuit 9, the envelope of the pulse group that causes the light source 1 to emit light at a specific frequency is extracted from this voltage change, and a control signal as shown in FIG.

Then, the switching circuit 10 is closed in synchronization with the intermittent light emission of the light source 1 by the control signal, and the light reception signal is transmitted to the light source 1.
The light is manually input to the signal processing circuit 7 in synchronization with the intermittent light emission.

As explained above, by having the above configuration, the present invention can detect a change in the supply current from the light receiving section side to the light emitting section side, and process the light reception signal in synchronization with the intermittent light emission of the light source. Therefore, it is possible to obtain a dimming type separate fire detector that does not require a special signal line for transmitting and receiving intermittent pulses between the light emitting part and the light receiving part, is easy to construct, and is made of SiN which is good against disturbance light.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an operation diagram showing the operating state of the sensor of the above embodiment. 1...Light source, 2...Light source 1 drive circuit,
4...Photoelectric conversion circuit, 5...Amplification circuit, 6...Filter circuit, 7...Signal processing circuit, 8...Current Change detection circuit, 9...
...Control signal generation circuit, 10...Switching circuit.

Claims (1)

[Claims] 1. A dimming-type separate fire detector that installs a light-emitting part with a light source and a light-receiving part that detects a light signal from the light-emitting part separately, and sends out an alarm signal by detecting a decrease in the amount of transmitted light due to smoke. The light emitting section is provided with an oscillation circuit that causes the light source to emit light intermittently at a specific frequency, and the light receiving section is provided with a current change detection circuit that detects a change in the current supplied to the light emitting section, and a current change detection circuit that detects a change in the current supplied to the light source. The present invention is characterized by comprising a control signal generation circuit that outputs a control signal in response to changes in the supply current due to intermittent light emission, and a switching circuit that inputs a received light signal to a signal processing circuit in response to this control signal. Dimming type separate fire detector.