| 摘要 |
A dust detecting circuit includes a sampling circuit and an alarm circuit. The sampling circuit has a first voltage amplifying circuit, a voltage comparing circuit, and a second voltage amplifying circuit. An input of the first voltage amplifying circuit is connected to an output of a dust sensor; two inputs of the voltage comparing circuit are respectively connected to a power supply for receiving a reference voltage and an output of the first voltage amplifying circuit. An output of the voltage comparing circuit is connected to an input of the second voltage amplifying circuit. An alarm circuit is connected to an output of the second voltage amplifying circuit. When the amount of the dust is more than a pre-determined threshold, a high level voltage signal is output from the sampling circuit to the alarm circuit, and the alarm circuit activates an alarm.
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