How much do you know about limit switches?

Author: Geym

Jun. 18, 2024

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A limit switch is an electrical switch used to limit the movement limit position of mechanical equipment. This type of switch has contact and non-contact types. The contact type is more intuitive. A travel switch is installed on the moving part of the mechanical equipment, and a limit position block is installed on the fixed point of relative movement, or the opposite installation position. When the mechanical contact of the travel switch hits the block, the control circuit is cut off (or changed), and the machine stops running or changes its operation. Due to the inertial movement of the machine, this travel switch has a certain "overtravel" to protect the switch from damage. There are many non-contact forms, and the common ones are reed switches, photoelectric types, induction types, etc.


Limit switches, also known as travel switches, can be installed on relatively static objects (such as fixed frames, door frames, etc., referred to as static objects) or moving objects (such as vehicles, doors, etc., referred to as animals). When the animal approaches the static object, the connecting rod of the switch drives the contact of the switch to cause the closed contact to be disconnected or the open contact to be closed. The circuit and motor are controlled by the change of the open and closed state of the switch contact.


Limit switch is a commonly used low-current master electrical appliance. The collision of the moving parts of the production machinery is used to make its contacts move to connect or disconnect the control circuit and achieve a certain control purpose. Usually, this type of switch is used to limit the position or stroke of the mechanical movement, so that the moving machinery automatically stops, reverses, changes speed or automatically moves back and forth at a certain position or stroke. In the electrical control system, the function of the limit switch is to realize sequential control, positioning control and position state detection. Used to control the stroke and limit protection of mechanical equipment.


Structure: It consists of an operating head, a contact system and a shell. In actual production, the limit switch is installed in a pre-arranged position. When the module installed on the moving parts of the production machinery hits the stroke switch, the contact of the limit switch moves to realize the switching of the circuit.


Therefore, the travel switch is an electrical appliance that switches the circuit according to the stroke position of the moving part. Its working principle is similar to that of a button. The limit switch is widely used in various machine tools and lifting machinery to control its stroke and perform terminal limit protection. In the control circuit of the elevator, the travel switch is also used to control the speed of opening and closing the car door, the limit of automatic opening and closing of the door, and the upper and lower limit protection of the car. The limit switch can be installed on relatively static objects (such as fixed frames, door frames, etc., referred to as static objects) or moving objects (such as vehicles, doors, etc., referred to as animals). When the animal approaches the static object, the connecting rod of the switch drives the contact of the switch to cause the closed contact to break or the open contact to close. The change of the open and closed state of the switch contact controls the action of the circuit and mechanism.


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