Automatic control circuit diagram of the range hood:

Working principle: In the figure, the gas -sensitive sensor and W1 composition of the gas detection circuit. The AC 5V voltage output by the power transformer output heated the gas sensor.

Anti -phase F1, W2, thermistor RT composition temperature detection circuit. The high potential signals output by the two -way detection circuit are controlled by the isolated diode VD8 and VD9 control circuits consisting of F2, F3, R2, VT2, and J1.

The light -sensitive resistance CDS, W3, F4, R3, VT3, J2 and other composition of lighting control circuits; IC1 is a music alarm circuit, controlled by gas detection circuit.

The component is selected from the IC1 to select the KD9561 integrated circuit; the F1 ～ F4 uses the CD4069 integrated circuit. VT1 ～ VT3 uses 9013 triode. The optical resistance uses CDS optics resistance; 4 330Ω thermist resistance is connected in thermal resistance. QM-N10 is selected. Other components are selected as shown in the figure.