JPS5852516Y2 - photoelectric smoke detector - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a photoelectric smoke detector, and its purpose is to provide a photoelectric smoke detector that prevents false alarms due to disturbance electrical noise.

The present invention will be explained in detail below with reference to embodiment figures.

Reference numeral 1 denotes a light emitting element, which is composed of, for example, a light emitting diode, and when the light from the light emitting element 1 is reflected and scattered by smoke A in the dark room, or its transmission is obstructed, the light receiving element 2 detects this and detects the smoke. The dark room is designed to detect the occurrence of smoke A, and the dark room is structured so that smoke A can be easily introduced and outside light cannot enter.

The light emitting element 1 is intermittently driven by the output of the oscillation circuit 3 to emit light. By causing the light emitting element 1 to emit light intermittently in this way, power consumption can be reduced and the power consumption during intermittent light emission can be reduced. The pulse width is narrowed to increase the peak of the light emitting current and improve the light emitting output.

2Fi is a light receiving element formed by, for example, a solar cell, and the output of this light receiving element 2 is amplified by an amplifier 4 and then waveform-shaped by a waveform shaping circuit 5.

6i/i one-shot circuit, which inputs the output of the waveform shaping circuit 5 and the output pulse of the oscillation circuit 3 via the transfer circuit 7, and outputs from both the waveform shaping circuit 5 and the oscillation circuit 3. This one-shot circuit 6 is triggered to output a signal having a fixed time width only when both exist simultaneously.

The output of the one-shot circuit 6 is integrated by an integrating circuit 8, and then its level is detected by a level detecting circuit 9, and when the occurrence of smoke A is detected, an alarm circuit 10 is driven.

The transfer circuit 7 inverts the output of the oscillation circuit 3 to form a synchronization pulse, and the operation of the one-shot circuit 6 is suppressed by this synchronization pulse.

Figure 2 shows one-shot circuit 6 in synchronization with the output of oscillation circuit 3.
In the case of a conventional circuit that does not operate, the time chart shows the buttons are pressed when noise is input synchronized with the emission pulse, when a continuous smoke detection signal is generated, and when noise is input that is not synchronized with the emission pulse. In the middle, a is the light emission pulse of the oscillation circuit 3 output, b is the synchronization pulse obtained by inverting the oscillation circuit 3 output in the transfer circuit 7, C is the output of the amplifier 4, d is the output of the one-shot circuit 6 without synchronization input, and e is the same as above. 8 outputs of the integrating circuit,
f indicates the output of the alarm circuit 10, respectively.

However, when noise synchronized with the light emitting pulse is input as shown in a of the same figure, if this noise input exceeds the detection level L1 that is pressed to the waveform shaping circuit 5, the one-shot circuit 6 is activated, as shown in d of the same figure. However, as shown in the figure e, the output of the integrating circuit 8 does not reach the detection level L2 of the next level detecting circuit 9 at 1, so the alarm circuit 10 does not perform an alarm operation.

When noise is input in synchronization with the light emission pulse in this way, even if the one-shot circuit 6 is operated in synchronization with the light emission pulse using the circuit of the present invention, the operation as shown in Fig. 2A will occur, but the light emission pulse Since it is considered that there is only one possibility that the signal and the noise are synchronized, there is little possibility of a substantial malfunction.

Next, when continuous smoke detection signals are generated as shown in Figure 2, all of them exceed the detection level L of the waveform shaping circuit 5, so this smoke detection signal is generated as shown in figure d. During this period, the one-shot circuit 6 generates an output signal, and the output of the integrator circuit 8 gradually increases as shown in the figure e and finally exceeds the detection level L2, and the alarm circuit 10 detects the occurrence of smoke as shown in the figure f. Performs notification alarm operation.

On the other hand, as shown in Figure 2 and 8, when noise like that shown in C in the same figure that is not synchronized with the light emission pulse is input, if this noise exceeds the detection level L0, the one-shot circuit 6tj that does not have the conventional synchronous operation function: As a result, the one-shot circuit 6 generates an output signal as shown in the figure d, and therefore the integrating circuit 8Iri generates an output signal that gradually rises as shown in the figure e, and after a certain period of time, this output signal changes. When the voltage level exceeds the detection level L2, the alarm circuit 10 performs an alarm operation due to a false alarm as shown in FIG.

However, in the circuit of the present invention, only signals synchronized with the light emission pulse are input to the one-shot circuit 6.
The one-shot circuit 6 will not operate due to noise as shown in C in FIG. 2, and therefore the alarm circuit 10 will not operate as a false alarm.

As described above, the present invention includes an oscillation circuit that causes a light emitting element to emit light intermittently and outputs an output pulse synchronized with the intermittent light emission of the light emitting element, and an output pulse from the light receiving element and the output pulse from the oscillation circuit. A one-shot circuit that outputs a signal for a certain period of time only when they exist simultaneously, an integrating circuit that integrates the output of the one-shot circuit, and a level detection circuit that detects the output level of the integrating circuit and drives an alarm circuit. Therefore, by intermittently synchronizing the light emission of the light-emitting element and the output of the light-receiving element, the shorter the length of the light-emission period of the light-emitting element is, the more likely it is to malfunction in response to noise that is thought to occur randomly over time. It is possible to significantly reduce the probability of smoke occurrence, and to stably detect smoke generation without being affected by disturbance electrical noise.
Furthermore, even if the one-shot circuit is driven due to coincidental noise synchronization, in order to gradually change the output level in the next-stage integrating circuit, the driving of the one-shot circuit once is at the level required to drive the level detection circuit. Therefore, the one-shot circuit and the integrating circuit have the advantage of intermittent synchronization of the light emission of the light-emitting element and the output of the light-receiving element, as well as greatly reducing the probability of false alarms of smoke detection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a time chart of a conventional example, where 1 is a light emitting element, 2 is a light receiving element,
3 is an oscillation circuit, 6 is an I/I one-shot circuit, 8 is an integration circuit, 9 is a level detection circuit, 10 is an alarm circuit, and A is a smoke.

Claims (1)

[Scope of utility model registration request] In a photoelectric smoke detector, the light from a light emitting element is emitted onto smoke introduced into a dark room, and the light transmitted or reflected by the smoke is detected by a light receiving element. , an oscillation circuit that outputs an output pulse synchronized with the intermittent light emission of the light emitting element, a one-shot circuit that outputs a signal for a certain period of time only when the output of the light receiving element and the output pulse from the oscillation circuit exist simultaneously; A photoelectric smoke detector comprising an integrating circuit that integrates the output of a shot circuit, and a level detection circuit that detects the output level of the integrating circuit and drives an alarm circuit.