JPS6349835Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a gas leak alarm, and in particular, a gas detection circuit that detects raw gas by a change in the resistance of a gas detection element, an alarm delay circuit, and an initial buzzer avoidance timer circuit that uses the charging time of a capacitor. The present invention relates to a gas leak alarm in which the output of the gas detection circuit is connected to the input of an alarm delay circuit together with the output of an initial buzzer avoidance timer circuit, and a buzzer connected to the output of the alarm delay circuit is sounded.

With conventional gas leak alarms, miscellaneous gas adheres to the gas detection element at the initial stage of energization, so
Even if there is no gas leak, the buzzer will sound to alert you. In order to prevent this, a long time timer (2 to 3 minutes) was used and the circuit was designed to not issue an alarm during this period. This timer circuit (hereinafter referred to as the initial buzzer avoidance timer circuit) has a large capacity,
A capacitor with a small leakage current was used, which was uneconomical. In addition, a piezoelectric buzzer is used for reliability, but its oscillation frequency is 2 to 3KH.
The sound was so high that it was harsh on the ears.

The purpose of this invention is to obtain a gas leak alarm that solves the above-mentioned drawbacks, and for this purpose, a pulse generation circuit that detects zero volts of the AC power supply and generates a pulse voltage is provided, and its output is input to the initial buzzer avoidance timer circuit. , an input of the alarm delay circuit, and a switching element, such as a transistor, for controlling a switching element, such as a transistor, of the buzzer.

An embodiment of the present invention will be described below with reference to the drawings. Reference numeral 1 denotes an AC power supply for applying power to a transformer 3 of a DC power supply such as a heater of the gas detection element 2 and a comparator to be described later. The output of the transformer 3 is connected to a diode bridge 4 to generate a full-wave rectified waveform, which is then smoothed by a diode 5 and a capacitor 6, and a constant voltage direct current is generated by a resistor 7, a transistor 8, and a Zener diode 9.
A gas detection circuit A is constituted by the gas detection element 2, resistors 10, 11, 12, and comparator 13.
The output of the diode bridge 4 is input, and the resistor 1
4, 15, 16, 17, 18, comparator 19
constitutes a pulse generation circuit D that generates a pulse voltage when the power supply voltage becomes zero volts, and resistor 3
An initial buzzer avoidance timer circuit C consisting of a transistor 37, a diode 20, resistors 21, 22, 23, a capacitor 24, and a comparator 25, which controls the transistor 34 which is the switching element of the buzzer 35 through the transistor 6;
8, 29, 30, a capacitor 31, and a comparator 32. The output of the initial buzzer avoidance timer circuit C and the output of the gas detection circuit A are connected to the capacitor 3 of the alarm delay circuit B.
Connect to 1. The output of alarm delay circuit B is resistor 3
3. A buzzer 35 is controlled via a switching element such as a transistor 34. The transistor 37 serves as a switching element for the transistor 34.

The effect of the above configuration is that immediately after the power is turned on, the gas detection element 2 has a low resistance value due to the adhesion of miscellaneous gases, so the output of the gas detection circuit A is at a high level. In the pulse generation circuit D, the full-wave rectified pulsating voltage outputs a high level near zero volts, and outputs a low level at other times, generating a pulse voltage with a frequency twice the power supply frequency.
Capacitor 24 of initial buzzer avoidance timer circuit C
is intermittently charged, but not enough, and the output is at a low level. Even if the transistor 37 is periodically turned on and off, the buzzer 35 does not sound. If you set the initial buzzer avoidance timer time to be longer than the time it takes for the miscellaneous gas on the gas detection element 2 to disappear, the gas detection element 2 will be activated after a certain period of time has passed.
The resistance value of the gas detection circuit A becomes high, and the output of the gas detection circuit A becomes low level. Thereafter, the output of the initial buzzer avoidance timer circuit C becomes high level. However, since the capacitor 31 is not charged, the output of the alarm delay circuit B is at a low level. Therefore, the buzzer 35 does not sound. This state continues if preparation is complete and there is no gas leak. When a gas leak occurs, the resistance value of the gas detection element 2 becomes low, the output of the gas detection circuit A becomes high level, the capacitor 31 is intermittently charged, and after a certain period of time, the output of the alarm delay circuit C becomes high level. level. Since the transistor 37 is intermittently turned on and off, the transistor 34 is intermittently turned on and off, and the buzzer 35 sounds intermittently.

As described above, according to the present invention, since both the capacitors of the alarm delay circuit and the initial buzzer avoidance timer circuit are charged intermittently, the capacitor capacity can be small, and the circuit that drives the buzzer intermittently can be shared without an oscillator. There are advantages. Furthermore, since the phases of charging the capacitors and driving the buzzer are reversed, there is an advantage that the shorter the charging time of both capacitors, the longer the driving time of the buzzer.

[Brief explanation of drawings]

The drawing is an electrical wiring diagram of a gas leak alarm showing an embodiment of the present invention. A...Gas detection circuit, B...Alarm delay circuit, C
...Initial buzzer avoidance timer circuit, D...Pulse generation circuit, 2...Gas detection element, 34, 37...
Transistor (switching element), 35...buzzer.

Claims (1)

[Scope of utility model registration request] A gas detection circuit that detects raw gas by the resistance change of the gas detection element, an alarm delay circuit, and an initial buzzer avoidance timer circuit based on the capacitor charging time are provided, and the output of the gas detection circuit is combined with the output of the initial buzzer avoidance timer circuit. In a gas leak alarm device connected to an input of an alarm delay circuit and a buzzer connected to an output of the alarm delay circuit via a switching element, a pulse generation circuit D is provided that detects zero volts of an AC power source and generates a pulse voltage, The output is connected to the input of the initial buzzer avoidance timer circuit C, the input of the alarm delay circuit B, and a switching element such as the transistor 37 that controls the switching element such as the transistor 34, and the capacitance of the capacitor 24 of the initial buzzer avoidance timer circuit C is A gas leak alarm device characterized in that a buzzer 35 intermittently sounds when the gas detection element 2 detects raw gas.