Natural gas stove flame alarm

Description: After the gas stove ignition, closing switch S, the circuit is operational. The phototransistor VT1, exposed to flame, remains in a low resistance state. This causes transistor VT2 to enter saturated conduction. Transistor VT3 and the integrated circuit (IC) are connected to the collector, which keeps the trigger terminal of the IC at a low potential, preventing it from functioning, and the speaker BL remains silent. If, during the combustion process, the gas stove unexpectedly goes out, VT1 will no longer receive strong light irradiation, leading to an increase in its internal resistance. Consequently, VT2 exits saturation, and the trigger terminal of the IC rises to a high level, activating the IC. This allows the music signal emitted by the crystal tube VT3 to amplify, prompting the speaker BL to issue a birdsong alarm to alert the owner to close the gas valve. The transistors VT1 and VT2 are rated at approximately 500.

The circuit operates as a safety mechanism for gas stoves, utilizing phototransistor VT1 to detect the presence of flame. When the stove is ignited and switch S is closed, the circuit enters a normal operating mode. The phototransistor VT1, under the influence of the flame, maintains a low resistance, which ensures that transistor VT2 is in a saturated state. This condition allows the circuit to keep the IC's trigger terminal at a low voltage, thus preventing any output signal from being generated, and the speaker BL remains inactive.

In the event that the flame goes out unexpectedly, the lack of light causes VT1 to increase its resistance, which in turn leads to the saturation state of VT2 being disrupted. As VT2 exits saturation, the voltage at the IC's trigger terminal rises, allowing the IC to become active. This activation results in the generation of a music signal from the crystal tube VT3, which is then amplified and sent to the speaker BL. The output is designed to produce a birdsong alarm, effectively alerting the user to the dangerous situation of a gas leak, prompting them to take immediate action to close the gas valve.

The circuit incorporates transistors VT1 and VT2, which are specified to handle currents of approximately 500 mA, ensuring that they can manage the necessary power levels without overheating or failing. This design is crucial for the reliability of the safety system, providing a robust response to the loss of flame and ensuring that the user is promptly notified of any potential hazards associated with gas usage.After the gas stove ignition, closing switch S, the circuit is in working condition. Phototransistor VT1 by flame before irradiation, low resistance state, the transistor VT2: saturated conduction, VT3 and integrated sheet music collector connected to the trigger terminal of the IC at a low potential, lC does not work, the speaker BL does not sound. If the gas stove in the combustion process for some reason suddenly went out, VT1 lose strong light irradiation, the internal resistance increases, VT2 exit saturation tends deadline, 1C trigger terminal is at a high level, Ic work, the music signal emitted by the crystal tube VT3 zoom promote BL issued birdsong alarm to alert the owner to close coal gas valve. In addition to the figure stated, transistors VT1 and VT2 of ~ 500.