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Working principle of rotary switch


Within a certain range, the resistance value is changed, and then there is a contact switch, which is the switch for old-fashioned televisions and radios. For fans, there are several gears, and several sets of lead wires from the fan winding are connected to change the speed by changing the number of wire turns. The principle is similar to that of a potentiometer, which usually consists of a resistor and a movable brush.

When the brush moves along the resistance body, it obtains a resistance value or voltage that is proportional to the displacement at the output end.

A rotary switch is a type of switch that uses a rotary handle to control the on/off of the main contact point. There are also two structural forms of rotary switches, namely single pole unit structure and multi pole multi position structure. Single pole unit rotary switches are often used in conjunction with rotary potentiometers in applications, while multi pole and multi position rotary switches are commonly used for switching working state circuits.

The common band switch and the gear shift switch of a multimeter are both rotary switches, with two types of structures: one is the BBM contact type, which is characterized by first disconnecting the front contact and then connecting the rear contact during shifting, with a state where both the front and rear contacts are disconnected.

Another type is the MBB contact type, which is characterized by a state where the moving contact is in contact with both the front and rear contacts during displacement. Then, the front contact is disconnected to maintain contact with the rear contact. In circuit design, the appropriate rotary switch should be selected based on the circuit purpose and circuit safety.

The rotary switch, due to its purpose, adopts a sealed structure as a whole, which has a certain waterproof effect and can basically reach the waterproof level of IP65. At the same time, it is necessary to use relatively hard and durable metal materials, with a difference in gear between 2nd or 3rd gear.