Natural gas stove flame alarm

  
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
Natural gas stove flame alarm - schematic

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.




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