JPS5852271B2 - Smoke detectors - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a smoke detector that detects smoke caused by a fire and obtains a switch output, and its purpose is to provide a smoke detector that shortens the time from power-on to transition to normal operation. The goal is to provide this with a simple configuration.

Figures 1 and 2 show the circuit configuration of a conventional smoke detector, where S is a constant voltage power supply section, and a time constant consisting of a resistor R1 and a capacitor C1 for delaying power-on time between a transistor Trl and a constant voltage diode ZD. It is connected to DC power supply B via a circuit.

Generally, when a smoke detector is connected to a plurality of lines, the purpose of providing such a time constant circuit is to solve the problem of an increase in rush current due to simultaneous power-on of each line.

By the way, in a smoke detector that is powered by a constant voltage power source S, when the DC power source B is turned on, a pulse signal is output from the oscillation circuit P, and a second pulse signal is sent to the output terminal of the field effect transistor FET via the ion chamber R. The voltage shown in the figure is generated and this voltage is applied to the non-inverting input terminal of the amplifier AMP of the amplifying section A2, but the inverting input terminal has a large capacitance due to the resistor R2 and low frequency AC amplification, so it is in a steady state. A capacitor C2 is connected which takes a considerable amount of time and therefore the voltage at the inverting input terminal charged through the feedback resistor R3 is
As shown in (■) in the figure, the power rises gradually from the power-on time t1 to the time t2.

The output voltage of the amplifying section A2 which receives the voltages (2) and (2) as input changes into a rising part, a linear part, and a falling part, as shown in FIG. A large change in the initial stage of FIG. 0 is taken out, and its integrated output is input to the comparator COM of the output section A4, where it is compared with the voltage of the constant voltage power supply section which rises as shown in FIG. 2 (2).

Therefore, the malfunction signal shown in FIG. 2 appears at the output of the comparator COM.

In order to eliminate such malfunction signals, the present invention provides a smoke detector that does not malfunction due to changes by bringing the output of the amplification section shown in FIG. 2C into a steady state in a short time.

Hereinafter, an embodiment of the smoke detector of the present invention will be described with reference to FIGS. 3 and 4, in which the same parts as in the conventional example are given the same reference numerals. Oscillator circuit P1 powered by voltage power source S1 Ion chamber R1 Smoke detection section A1 consisting of a field effect transistor FET, amplification section A2 that amplifies the output of the field effect transistor FET, and the difference between the non-detection signal and the detection signal. In the smoke detector, the amplifying section A2 is connected to an amplifier AMP and the output side of the amplifier AMP. An input resistor R2 and a capacitor C2 are connected to the original input terminal of the amplifier AMP, and a feedback resistor R3 and a diode d1 are connected between the output terminal and the inverting input terminal of the transistor Tr2.
This smoke detector is characterized in that it is connected through a parallel circuit.

According to the present invention, when the constant voltage power supply section S is connected, the operating output of each section will rise slightly at the initial stage as shown in Fig. 4 due to the time constant determined by the resistor R1 and the capacitor C1. , the amplifier AMP of the amplifier section A2 is
A resistor R is connected between the output transistor Tr2 and the inverting input terminal.
3 and a diode d1 through a parallel circuit, and a high-capacity capacitor C2 is rapidly charged through the same parallel circuit.

Therefore, the inverting input terminal is connected to the conventional resistor R shown in Figure 4 ■.
It starts up and stabilizes in a much shorter time than in the case of only 3.

Therefore, the output of the amplifier AMP becomes stable in a short time after the power is turned on, as shown in FIG. 4, and enters a steady state.

This change in the amplified output is integrated by the signal processing section A3 and compared with the output shown in Figure 4 (■) by the comparator COM of the output section A4, ensuring that no malfunction output from the comparator COM occurs.
Become.

As described above, according to the present invention, the smoke detection section, the amplification section, the signal processing section, and the output section are connected so that a power supply voltage is applied by a constant voltage power supply circuit including a time constant circuit, and the amplification section has a smoke detection section, an amplifier section, a signal processing section, and an output section. The amplifier output is fed back to an input circuit consisting of a resistor and a capacitor connected to one input terminal of the amplifier through a feedback resistor, and the output of the signal processing section, which extracts and integrates the output change of the amplifier section, is input to the output section. In the smoke detector thus constructed, by connecting a diode in parallel with the feedback resistor, the amplifier output can be brought to a steady state in a short time after power is turned on, and the smoke detector can operate normally. It is a smoke detector.

[Brief explanation of the drawing]

1 and 2 show a conventional example, where FIG. 1 is a circuit diagram and FIG. 2 is a time chart of the operation of each part. 3 and 4 show an embodiment of the smoke detector of the present invention, FIG. 3 is a circuit diagram, and FIG. 4 is a time chart of the operation of each part. S... Constant voltage power supply section, B... DC power supply, Trl... Transistor, ZD...
Constant voltage diode, R1... Resistor, C1...
...Capacitor, A1...Smoke detection section, P...
・・・・Oscillation circuit, R・・・・Ion chamber, FET・
...Field effect transistor, A2...Amplification section, AMP...Amplifier, Tr2...
Transistor, R3... Feedback resistor, dl...
...Diode, R2...Resistance, C2...
... Capacitor, A3 ... Signal processing section, A4
...Output section, COM...Comparator, R,, R, ...Resistance.

Claims (1)

[Claims] 1 A smoke detection section, an amplification section, a signal processing section, which are connected so as to apply a power supply voltage by a constant voltage power supply circuit including a time constant circuit,
and an output section, which feeds back the amplifier output of the amplification section through a feedback resistor to an input circuit consisting of a resistor and a capacitor connected to one input terminal of the amplifier, and extracts and integrates the changed output of the amplification section. 1. A smoke sensor configured to input the output of a signal processing section to an output section, characterized in that a diode is connected in parallel with the feedback resistor.