JPS632957Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gas leak alarm device suitable for home use.

This invention is equipped with a circuit that stabilizes the plate voltage of the gas detection element in order to improve characteristics changes due to fluctuations in the power supply voltage of the gas detection element, and prevents false alarms due to unstable operation of the gas detection element during initial energization. It is equipped with an indicator that emits light when the signal from the gas detection element exceeds the signal level corresponding to the alarm concentration and during the initial period until the operation of the gas detection element stabilizes. The switch is equipped with a circuit that suppresses the operation of the buzzer for a predetermined period of time from the time of gas detection in case a high concentration gas is detected, and the switch is equipped with a circuit that suppresses the operation of the buzzer for a predetermined period of time from the time of gas detection. It is an object of the present invention to provide a gas leak alarm device equipped with a circuit that modulates the buzzer sound intermittently in order to draw more attention to the sound of the buzzer.

Hereinafter, preferred embodiments of the present invention will be described in detail as illustrated in the accompanying drawings.

A gas leak alarm device generally operates using a gas detection element, a comparator that compares a detection signal from the detection element with a signal corresponding to an alarm concentration, and an alarm signal from the comparator. Basically, it is equipped with a buzzer.

In the drawing, the gas detection element 1 connects one of its heater terminals to the DC stabilization circuit 2 to stabilize the plate voltage, thereby preventing the operating point of the gas detection element 1 from shifting due to fluctuations in the power supply voltage. suppresses changes in characteristics.

The aforementioned comparator 3 receives at its inverting input the signal from the gas detection element 1 in a suitably divided form, and at its non-inverting input receives a level corresponding to the alarm concentration relative to the signal level given to the inverting input. is received as a reference signal.

The output of comparator 3 is connected to the base of transistor 4. The emitter of this transistor 4 is connected to ground, and the collector is connected to a power supply line stabilized by a stabilizing circuit 5 via a load resistor, as well as a light emitting indicator 6 and an alarm delay circuit 7.
connected to.

The light emitting indicator 6 consists of a transistor 8 and a light emitting diode 9, and when the comparator 3 detects a gas leak, its output becomes low level, and the transistor 4 turns on.
It acts to light the light emitting diode 9 while it is off. This light emitting indicator 6 is also connected to an initial energization delay circuit 10, which will be described later, so that the light emitting diode 9 is turned on while this delay circuit is operating.

The alarm delay circuit 7 includes a comparator 11, the inverting input of which is connected to a charging circuit made up of a resistor and a capacitor, and the non-inverting input connected to a reference voltage source made of a resistor. When waiting for gas leak detection, transistor 4 is on, so the current that should flow into charging capacitor 12 flows through diode 13 and transistor 4, so the inverting input of comparator 11 is always at a low level, and the output is at a high level. It's summery. When a gas leak is detected, transistor 4 is turned OFF and diode 13 is turned OFF as the cathode reaches a high level, so the charging circuit is activated, and after a predetermined period of time (for example, 20 seconds), the inverting input level exceeds the non-inverting input level. As a result, the comparator output level becomes low level.

A normally closed switch 14 to which the charging capacitor 12 is connected in series is used when inspecting this alarm device. That is, the switch 14 is opened in advance when the inspection gas is sprayed onto the gas detection element 1. For example, when the inspection gas container is inserted into the inspection port, the switch 14 is opened in conjunction with the insertion. In this case, no charging circuit is formed, so when gas is detected, the diode 13
OFF, the inverting input of the comparator 11 immediately becomes high level, and the output becomes low level. In other words, the alarm delay circuit 7 does not function.

The output of the alarm delay circuit 7 is connected to the oscillation circuit 15. The oscillation circuit 15 includes an oscillation suppressing transistor 16 and an oscillator using an operational amplifier 17, and operates when the transistor 16 is off. While waiting for a gas leak, the inverting input of the amplifier 17 is at a low level because the transistor 16 is ON, so the output is at a high level and the output transistor 18 is at a low level.
When ON, its collector potential is at a low level. When detecting a gas leak, the transistor 16 is turned off.
The high level of the output of the amplifier 17 starts charging the capacitor 20 via the resistor 19, and when the potential across the capacitor 20, that is, the inverting input level of the amplifier 17 exceeds the non-inverting input level, the output level is inverted and becomes low. Therefore, the charge in the capacitor 20 is discharged through the resistor 19, and when the inverting input level becomes lower than the non-inverting input level, the output level is inverted again and becomes a high level, and the oscillation operation is repeated.

The oscillation signal appearing at the collector of the output transistor 18 is applied to the buzzer driving transistor 24, causing the buzzer 25 to sound intermittently.

The energization delay circuit 10 includes a comparator 21 and a control transistor 22, and the inverting input of the comparator is connected to a reference voltage source, and the non-inverting input is connected to a charging circuit. This energization delay circuit 10 operates until a predetermined period of time (for example, about 3 minutes) has elapsed after the start of energization.
The purpose is to stop the function of this alarm device, and in reality, the control transistor 22 inserted in series in the circuit of the buzzer 25 is stopped for the predetermined period of time.
This is accomplished by turning it off. That is,
Since the inverting input exceeds the non-inverting input until a predetermined time elapses from the start of energization, the output of the comparator 21 is at a low level, and the transistor 22 is controlled to be OFF, and after a predetermined time the output is inverted and thereafter becomes high. level, and transistor 22 remains on. Note that the output of the comparator 21 is at a low level while the predetermined time has elapsed, so even if the transistor 8 is OFF, the circuit of the light emitting diode 9 (light emitting display 6) via the diode 23 is closed, and the light is displayed during this period. It turns out.

[Brief explanation of drawings]

The drawing is a diagram showing an example of a circuit of a gas leak alarm device according to the present invention. 1... Gas detection element, 2, 5... Stabilization circuit,
3... Comparator, 6... Light emitting indicator, 7... Alarm delay circuit, 9... Light emitting diode, 10... Energization delay circuit, 25... Buzzer.

Claims (1)

[Scope of utility model registration request] In a gas leak alarm device that includes a gas detection element, a comparator that compares a signal corresponding to an alarm concentration with a signal from the element, and a buzzer that notifies a gas leak, the plate voltage of the gas detection element is a stabilizing circuit; a power-on delay circuit that disables the circuit operation of the buzzer for a predetermined period of time during initial power-on to prevent false alarms due to initial unstable operation; and a power-on delay circuit that prevents false alarms due to initial unstable operation; an indicator that emits light for a period of time until the circuit elapses for a predetermined time;
an alarm delay circuit that disables the circuit operation of the buzzer for a predetermined period after the comparator detects a gas leak to prevent false alarms due to the passage of transient high concentration gas; The alarm delay circuit includes a switch for disabling the operation of the time delay circuit, and an oscillation circuit that controls the operation of the buzzer intermittently based on the alarm signal from the comparator given by the alarm delay circuit after a predetermined time has elapsed. Gas leak warning device.