The household fuel gas alarm circuit

Published:2011/7/6 22:36:00 Author:qqtang | Keyword: household, fuel gas alarm | From:SeekIC

The working principle of the device circuit is shown in figure 1. The circuit consists of the power supply circuit, sensor circuit, voltage control oscillator and alarm circuit, etc. The 220V mains is dropped to 5.5V or so by the power supply transformer T1, which is taken directly as the heating voltage of the sensor QM－N10 without rectification and filter. The control circuit is powered after it is rectified by U and filtered by C1. The resistance of the air sensitive resistor sensor QM-N10 is about dozens of kΩ in clean air, when it contacts with harmful gas, the conductance will rise up.



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