JPS6327278Y2 - - 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 resistance of a gas detection element, an alarm delay circuit, and an initial buzzer avoidance timer circuit based on the charging time of a capacitor. This invention relates to a gas leak alarm device in which the output of the gas detection circuit is connected to the input of the alarm delay circuit together with the output of the initial buzzer avoidance timer circuit, and the 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.
Even if there is no gas leak, the buzzer will sound to alert you. In order to prevent this, a device consisting of a timer circuit that uses a long timer (2 to 3 minutes) and does not issue an alarm only during this period was provided. This timer circuit (hereinafter referred to as the initial buzzer avoidance timer circuit) uses a capacitor with a large capacity and a small leakage current, and is therefore uneconomical. In addition, a piezoelectric buzzer was used for reliability reasons, and the oscillation frequency of this buzzer was as high as 2 to 3 KH, making it a harsh sound.

The purpose of this invention is to obtain a gas leak alarm that solves the above-mentioned drawbacks.To achieve this purpose, a power oscillation circuit is provided, and this output is connected to the input of the initial buzzer avoidance timer circuit, the input of the alarm delay circuit, and the buzzer. These are connected to each other.

An embodiment of the present invention will be described below with reference to the drawings. The AC power supply 1 is a power supply for a transformer 3 for the heater of the gas detection element 2, a diode 4, a capacitor 5,
A DC power supply A for a comparator, etc., which will be described later, consisting of resistors 6 and 7, a transistor 8, and a Zener diode 9.
becomes. Gas detection element 2, resistors 10, 11, 1
2. The comparator 13 constitutes the gas detection circuit B, and its output is connected to the resistors 15, 16, 17, 18,
Connect to the input of an alarm delay circuit C consisting of a capacitor 19 and a comparator 20. The output of the alarm delay circuit C is connected via a resistor 21 to a transistor 23 that drives a buzzer 22. Resistance 24, 25, 2
6, 27, 28, a capacitor 29, and a comparator 30 constitute a relaxation oscillation circuit D, and its output is input to an initial buzzer avoidance timer circuit E consisting of a diode 31, resistors 32, 33, 34, a capacitor 35, and a comparator 36. It is also connected to the input of the alarm delay circuit C, and to the transistor 23 via a resistor 37 and a transistor 38. The above is an intermittent sound circuit when issuing an alarm. The output of the initial buzzer avoidance timer circuit E is connected to the input of the alarm delay circuit C, ie, to the capacitor 19.

The effect of the above configuration is that immediately after the power is turned on, the resistance value of the gas detection element 2 of the gas detection circuit B is low due to the adhesion of miscellaneous gases, so the output of the gas detection circuit B is at a high level. . The relaxation oscillation circuit D periodically outputs high level and low level. The capacitor 35 of the initial buzzer avoidance timer circuit E is intermittently charged, but not sufficiently, and the output is at a low level. Therefore, the alarm delay circuit C
capacitor 19 is not charged. Therefore, the output of the alarm delay circuit C is at a low level. Although the transistor 38 is periodically turned on and off, the transistor 23 is turned off, so the buzzer 22 does not sound. Since the timer time of the initial buzzer avoidance timer circuit E is said to be longer than the time required for the miscellaneous gas attached to the gas detection element 2 to disappear, the resistance value of the gas detection element 2 increases after a certain period of time has passed. Therefore, the output of gas detection circuit B becomes low level. Thereafter, the output of the initial buzzer avoidance timer circuit E becomes high level. however,
Since the capacitor 19 is not charged, the output of the alarm delay circuit C is at a low level. Therefore, the buzzer 22 does not sound. This state remains if the preparation is completed and no gas leaks.

Next, when a gas leak occurs, the resistance value of the gas detection element 2 becomes low, the output of the gas detection circuit B becomes high level, the capacitor 19 is intermittently charged, and after a certain period of time, the alarm delay circuit C is activated. The output becomes high level and the transistor 23 is turned on. Since the transistor 38 is intermittently turned on, the buzzer 22 sounds intermittently.

As described above, according to the present invention, since both the capacitors of the circuits C and E are charged intermittently, the capacitor capacity can be small, making it economical, and since the buzzer 22 is driven intermittently, the alarm sound is not harsh to the ears. It has the effect of disappearing.

Note that the same effect can be obtained even if the alarm delay circuit C is replaced with a timer or the like other than the one in the embodiment.

[Brief explanation of the drawing]

The drawing is an electrical wiring diagram of a gas leak alarm showing an embodiment of the present invention. A...DC power supply, B...Gas detection circuit, C...
Alarm delay circuit, D...relaxation oscillation circuit, E...initial buzzer avoidance timer circuit, 2...gas detection element,
22...buzzer, 35...capacitor.

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 that is connected to the input of the alarm delay circuit and a buzzer is connected to the output of the alarm delay circuit, a relaxation oscillation circuit D is provided, and its output is connected to the initial buzzer avoidance timer circuit E.
is connected to the input of the alarm delay circuit C and the buzzer 22, and reduces the capacitance of the capacitor 35 of the initial buzzer avoidance timer circuit E, and also turns on and off the buzzer 22 by detecting raw gas of the gas detection element 2. A gas leak alarm that is characterized by a specific sound.