JPH0421184Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention is a photoelectric type in which an emitter and a receiver are arranged facing each other at a predetermined distance, and an alarm is issued by sensing the attenuation of light due to the intrusion of smoke between the emitter and receiver. The present invention relates to a separate type sensor, and particularly to a circuit configuration of a light projector.

[Conventional technology]

Japanese Patent Application Laid-Open No. 52-53699 is known as a so-called separate type fire detector in which a projector and a receiver are arranged facing each other at a predetermined distance (5 to 100 m), in which the projected light is modulated. .

[Problem that the invention seeks to solve]

This kind of conventional fire detector is equipped with a fundamental frequency oscillator and a pulse oscillator for modulation, which are kept in operation at all times, and the average current consumption is large, making it difficult to use such a separate type detector as a conventional fire receiver. When multiple units were connected to different railroad tracks, there were problems such as alarm relays being activated by the monitoring current.

[Means to solve the problem]

This device is a photoelectric separation type sensor that detects fire by arranging a light emitter and a light receiver facing each other at a predetermined distance and detecting the attenuation of light due to the intrusion of smoke between the light emitter and light receiver. a first oscillator that generates a small pulse of , a stretching circuit that stretches the pulse, and a second oscillator driven by the stretching circuit that modulates the stretched pulse at a relatively high frequency;
A waveform shaping circuit that cuts the rising edge of the output of the second oscillator is provided, and the above problem is solved by configuring the light emitting element to be lit by the output of the waveform shaping circuit. It is.

[Effect]

As a result, the second oscillator, which generates a relatively high frequency, operates intermittently, so that the average current consumption of the projector becomes extremely small.

〔Example〕

Figure 1 is a block diagram showing the circuit configuration of the separate sensor of this invention, Figure 2 is a diagram showing the specific circuit of the light projecting section in Figure 1, and Figure 3 shows the operation of the circuit in Figure 2. Each figure shows a time chart for explanation, and the same parts in each figure are shown using the same symbols.

The projector 1 includes an oscillator 2 that generates pulses with an extremely small duty ratio as shown in the waveform of FIG. A second oscillator 4, a waveform shaping circuit 5, an amplifier 6, and a light emitting element LED are respectively provided.

In addition, the light receiver 7 includes a light receiving element PD and an amplifier 8.
, a filter 9, a signal processing circuit 10, and an alarm indicator 11.

The pulse shown in FIG. 3a generated by the first oscillator 2 becomes a pulse shown in FIG.
is applied to The output of the second oscillator 4 is shown in Fig. 3c.
Since the rising part is deformed as shown in FIG. 3, this output has the rising part cut off by the waveform shaping circuit 5, and becomes a modulated waveform as shown in FIG. 3d. This modulation waveform is applied to the light emitting element LED.

The light from the light emitting element LED of the emitter 1 is transmitted to the receiver 7.
If smoke from a fire or the like enters during this period, the amount of received light will be attenuated, and when this value falls below a predetermined value, the signal processing circuit 10 will generate an output and the alarm indicator 11 will be activated. Driven.

Note that the modulation prevents false alarms due to extraneous light.

FIG. 2 shows a specific circuit example of the projector 1. In the figure, the first oscillator 2 consists of two transistors T _r1 ,
The pulse stretching circuit 3, which consists of a blocking oscillator consisting of T _r2 , a capacitor C ₁ and an inductance L, and to which this output is applied, is a one-shot multi-circuit consisting of two NAND gates 31 and 32 made of CMOS, or The second circuit driven by the output of this one-shot multi-circuit 3
The oscillator 4 consists of a NAND gate 41 and a capacitor.
C ₂ , a CR oscillator consisting of resistors R ₁ and R ₂ , and a CMOS NAND gate 5 as the waveform shaping circuit 5. This NAND gate 5 cuts the rising part of the output of the second oscillator 4. Ru.

The output of the NAND gate 5 is applied to the base electrode of the transistor 6, which is an amplifier, and the light emitting element
The LED is turned on with a modulated pulse as shown in Figure 3d.

In this example, the intermittent light emission period T and the pulse generation period t are T = 400 msec, t ₁ = 1 msec, t ₂ =
Although it is set to 10 μsec, it is not limited to this, and it is sufficient to set T≫t ₁ >>t ₂ , and as a result, the average current consumption becomes extremely small. In particular, the current consumption of each circuit 3, 4, and 5 using NAND gates during the rest period of the output pulse (T' in Figure 3) is extremely small.
It becomes negligible.

[Effect of idea]

The decoupled sensor of this invention drives the fundamental frequency oscillator of the modulated pulse intermittently as described above, and cuts out the deformed waveform at the rising edge, resulting in extremely low average current consumption and errors caused by waveform deformation. It also has features such as being able to prevent alarms and being able to be used by being connected to the sensor connection line of a general fire receiver.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the circuit configuration of the photoelectric separation type sensor of this invention, Fig. 2 is a diagram showing a specific circuit of the light projecting section of Fig. 1, and Fig. 3 is a diagram showing the circuit configuration of the photoelectric separation type sensor of this invention. A time chart is shown to explain the operation. DESCRIPTION OF SYMBOLS 1... Emitter, 7... Light receiver, 2... First oscillator, 3... Enlargement circuit, 4... Second oscillator, 5... Waveform shaping circuit, LED... Light emitting element,
PD...Photodetector.

Claims (1)

[Scope of utility model registration request] In a photoelectric separation type sensor that detects a fire by arranging a light emitter and a light receiver facing each other at a predetermined distance and detecting the attenuation of light due to the intrusion of smoke between the light emitter and receiver, a pulse with a small duty ratio is used as the light emitter. a first oscillator that generates a pulse, a stretching circuit that stretches the pulse, a second oscillator driven by the stretching circuit that modulates the stretched pulse at a relatively high frequency; 1. A photoelectric separation type sensor comprising a waveform shaping circuit that cuts a rising edge of an output of an oscillator, and a light emitting element is lit by the output of the waveform shaping circuit.