Tag: limit switch

Limit switches are used to control the travel and limit protection of mechanical equipment. In actual production, the travel limit switch is installed in a pre-arranged position. When the module installed on the moving parts of the production machinery hits the travel switch, the contacts of the travel limit switch act to realize the switching of the circuit. Therefore, the limit switch is an electrical appliance that switches the circuit according to the travel position of the moving part, and its working principle is similar to that of a button. Limit switches are widely used in various machine tools and hoisting machinery to control their travel and perform terminal limit protection. In the control circuit of the elevator, the travel limit switch is also used to control the speed of opening and closing the car door, the limit of automatic door opening and closing, and the upper and lower limit protection of the car.

The limit switch is a commonly used small current master electrical appliance. It utilizes the collision of the moving parts of the production machinery to make or break the control circuit to achieve certain control purposes. Usually, this ATO limit switch is used to limit the position or stroke of mechanical movement, so that the moving machinery can automatically stop, reverse movement, variable speed movement or automatic round-trip movement according to a certain position or stroke.

Introduction of limit switch
Limit switch is a kind of sensor to detect and control the mechanical movement beyond the limit displacement. For example, the position limiter of electric rolling shutter gate ensures that the motor will stop working when the gate is opened or closed to the specified position, so as to ensure that the motor and mechanical components will not be damaged due to excessive work. The commonly used limit switches include all kinds of travel switches, micro switches, and photoelectric switches. In short, as long as the corresponding detection device is equipped and the functional requirements are completed, they can be used as limit switches.

The difference between limit switch and proximity sensor:

1. Proximity sensors are non-contact switches with a long life and are suitable for passing objects. Limit switches are contact switches. Due to the internal contacts, the working life is relatively shorter.
2. Limit switches are used for position detection in one direction. For two-way position detection, using a proximity sensor is better.
3. Use limit switch for protection function. Use a proximity sensor to detect when an object passes a certain point.
4. The limit switch usually has 1 NO + 1 NC contacts. Generally only one group of contacts is used, so there are 2 wires. Proximity sensors generally adopt 2-wire, 3-wire and 4-wire, so they have more wires than limit switches. Some proximity sensors have to confirm it is PNP or NPN based on the connected equipment.

Limit switch is a device that makes use of the collision of the machine moving parts to make the contacts operating to realize the control circuit is turned on or off, so as to achieve a certain control purpose. It cooperates with other devices to form more complex automation equipments in industry. Therefore, selecting more suitable limit switches will make the entire automatic control system becomes more reasonable and efficient.