Schematic diagram of automatic exhaust switch circuit

Probe domestic switch needle KG-300K needle head diameter is 3.0mm normally open switch needle

Crystal oscillator 2.5*2.0mm 2520 0.67M~170M OSC can be supplied at any frequency

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The circuit works of the device: when the room is clean air, the conductivity of the gas-sensitive semiconductor tube HQ-II is very low, the voltage drop on R2 is small, and the voltage value cannot cause DW2 breakdown, so LSE 1, 2 The foot is disconnected. At this time, the 4 pin of the LSE outputs a low level, the relay J is in the released state, and the exhaust fan does not work. Once harmful gases are present in the room, the concentration gradually increases, resulting in an increase in the conductivity of the gas sensing tube HQ-II, so the voltage drop generated on R2 rises and rises to a certain value, DW2 (DW, the data warehouse) Is a topic-oriented, integrated, relatively stable, historically-changing collection of data used to support management decisions. This definition was written in the book Building the Data Warehouse by Bill Inmon, the father of the data warehouse, in 1991. It is proposed that the breakdown is turned on and the triode VT is also turned on. When VT is turned on, the resistance between pins 1 and 2 of the LSE becomes small, and the 4 feet of the LSE become a high level, so that the relay J is energized, the exhaust fan is turned on, and harmful gases are discharged to the outside in time.

Automatic exhaust switch circuit principle