1、 Types of fan rotary switch:

There are two types of fan rotary switches. Today's fans generally directly adjust the number of motor coil turns to change the motor speed of the electric fan. This kind of fan is cheap and has a short service life. In the past, the electric fan switch was actually a transformer. Adjust the motor terminal voltage to change the motor speed of the electric fan. Now the fan has several gears. Change the fan speed through the fan rotation switch. The common fan speeds are: off low speed high speed off, or off low speed high speed off low speed + shake head high speed + shake head off.

2、 The working principle of switch

As the name suggests, the rotary switch is a kind of switch that uses the rotary handle to control the on-off of the main contact point. There are also two structural forms of rotary switch, namely unipolar unit structure and multipole multi element structure. Unipolar unit rotary switch is often used together with rotating shaft potentiometer in application, while multipole multi element rotary switch is mostly used for switching lines in working state.

Its working principle is: change the resistance value within a certain range, and then there is a contact switch, which is the switch of old-fashioned TV and radio. The current fan has several gears, which are connected with several groups of outgoing lines of fan winding, and change the speed by changing the number of turns. The principle is similar to that of potentiometer.

The common band switch and the shift switch of the multimeter are rotary switches, which have two structures: one is the BBM (break before make) contact type, which is characterized in that when shifting, the moving contact first disconnects the front contact and then connects the rear contact, in which there is a state disconnected from both the front and rear contacts; the other is the MBB (make before break) contact type, which is characterized in that when shifting, the moving contact has a state in contact with both the front and rear contacts. Then disconnect the front contact and keep in contact with the rear contact. In the circuit design, the appropriate rotary switch shall be selected according to the purpose and safety of the circuit.