Limit switches, also known as travel switches, are electrical switches used to restrict or detect the position of moving objects in mechanical devices. Its working principle is mainly based on the position sensing of objects or direct contact to achieve control of the circuit. The following is a detailed analysis of the working principle of the limit switch:

I. Overview of Working Principle

Limit switches sense the position of objects through mechanical triggers and are connected to electrical circuits through conductive contacts. When an object comes into contact with or approaches the limit switch, the mechanical trigger will be activated, causing a change in the state of the conductive contact. This change can be detected by the control loop and trigger corresponding operations as needed, such as stopping the equipment operation, changing the running direction or initiating other actions.

Ii. Classification of Working Methods

The working modes of limit switches can be divided into two types: proximity type and contact type.

Proximity limit switch

Principle: Determine the position of an object by sensing signals such as its magnetic field, infrared rays, and ultrasonic waves.

Working process: When an object approaches the limit switch, the sensing device will receive the signal and convert it into an electrical signal. This electrical signal is transmitted to the control loop, thereby triggering the corresponding operation.

Application scenarios: It is suitable for scenarios that require non-contact detection, such as avoiding mechanical collisions and improving detection accuracy.

Contact limit switch

Principle: Sense the position of an object through direct contact with it.

Working process: Install limit switches on the moving parts of mechanical equipment and limit position stop blocks on the fixed points of relative motion. When the mechanical contact of the limit switch touches the stop block, it will cut off or change the control circuit, causing the machinery to stop running or change its operation.

Due to the inertial movement of the machinery, this type of limit switch usually has a certain "over-travel" design to protect the switch from damage.

Iii. Composition and Characteristics

Limit switches are usually composed of trigger devices, conductive contacts and control circuits. Its characteristics include:

High precision: It can accurately sense the position of an object and trigger corresponding actions.

High reliability: It can maintain stable performance even in harsh working environments.

Easy to install and maintain: The structure is relatively simple, and installation and maintenance are both convenient.

Iv. Application Scenarios

Limit switches are widely used in various machine tools, lifting machinery, elevators and other equipment to control the travel of the equipment and provide terminal limit protection. In industrial automation control systems, limit switches also play an important role, being used to achieve functions such as sequential control, positioning control, and position state detection.

In conclusion, limit switches achieve position restriction and detection of mechanical devices by sensing the position of the object or direct contact. Its working principle is simple and reliable, and it plays an important role in the fields of automatic control systems and machinery.