How does limit switch work

Limit switches are a practical solution for sensing in most situations. There are, however, a few disadvantages to using limit switches.

Some of the strengths and weaknesses are listed below:. Pretravel : the distance or angle that the actuator must go through to trip the contacts.

Operating Point : position of the actuator at which the contacts snap to the operated position. Release Point : the position of the actuator at which the contacts return to their original state. Initial Position : position of actuator when no external force is ap-plied to the actuator.

Minimum return force torque : minimum force required to return actuator to its initial position. Repeat Accuracy : ability of a switch to repeat its characteristics precisely from one operation to the next operation.

The actuator is the part of the switch which physically comes in contact with the target. In some limit switches, the actuator is attached to an operating head which translates a rotary, linear, or perpendicular motion to open or close the electrical contacts of the switch.

While there are a number of different styles of limit switches available in the market today, this manual will describe two classes of limit switches — standard industrial oiltight and precision switches.

Levers and roller levers actuate radially, that is they rotate on an axis. Roller levers are tipped with a roller to lessen the friction and the force required to activate the lever. Levers spring-return to neutral when the force is removed.

This is one of the most popular styles of switch operators. Similar to a standard roller lever, but the length of the lever is adjustable anywhere from a few millimeters to up to 5 centimeters. The rollers are also available in various diameters.

Plunger heads come in many varieties and sizes. Plungers are actuated by a perpendicular force applied directly to the end of the plunger. A linear actuator is a common electro-mechanical component used in many applications. The unit is highly customizable and can be modified to fit into different environments and meet various functional demands. There are many sensors available to utilize linear actuators positional feedback feature.

In this article, we will discuss how a linear actuator with a limit switch works and linear actuator limit switch wiring to fully understand feedback control. How does a limit switch work and what is the function of a limit switch inside a linear actuator? A mechanical limit switch is a component that is responsible for ensuring the device does not extend nor retract outside its mechanical dimension.

An electric linear actuator moves as its motor spins, which drives the acme screw to push the shaft rod out or pull it in. The direction of the motor spin determines the direction of the shaft rod movement. However, without a mechanical limit switch, there are no stop points on neither end of the travel.

The motor will only stop when the user manually turns off the power to the unit. This could cause a safety concern if the actuator travels to its mechanical limitation, but the motor is still running.

The motor will stall when it can no longer rotate, causing a high current draw, and eventually burning out the motor. To prevent this, a set of mechanical limit switches or hall effect sensors are installed in all Progressive Automations actuators.

A linear actuator with a limit switch implements a mechanical trigger at either end of the travel, and the trigger causes the motor to shut off at the end of its travel. The circuit below is how our linear actuators are connected to limit switches.

Instead of using the mechanical trigger to shut off the motor, the application prefers to have an analog signal as part of an integrated control system. Currently, Progressive Automations offer two different configurations when it comes to limit switch feedback. The extended limit switch and the retracted limit switch will provide an individual signal of normally open and closed to the users. Save my name, email, and website in this browser for the next time I comment.

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