Exploring Limit Switches; Your Essential Guide

A limit switch is a highly robust device that uses the contact of a moving part to activate the switch actuator which triggers the electrical contacts, allowing the circuit to be turned on or off for a specific control purpose.

Limit switches are simple cost effective devices with highly predictable and consistent performance. They can switch high inductive loads and are not affected by electromagnetic noise. Understanding and selecting appropriate limit switches will improve the overall efficiency and logic of the control system.

Here are some key points for choosing limit switches:

The Switch body

The material of the limit switch body varies depending on the environment it is being used in and the frequency of use. For commercial applications and low frequency use, the body is typically a type of plastic. For industrial applications and high frequency use, aluminium is the go to spec. For extremely harsh environments, stainless steel may be the best option.

The Switch Actuator

Different actuators are selected according to the shape and movement direction of the detection target. Common types of actuators include roller plunger, top plunger, roller lever, adjustable roller lever, simulated roller lever, adjustable rod, fork lever, coil spring, and more.

Electrical Requirements

Select the limit switch according to the rated voltage and current of the control circuit. Most limit switches are rated to 250Vac switching 5 Amps. Heavier switching capacities of 15 Amps are possible.

Contact Blocks

According to different needs, contact block options are typically single pole normally open and normally closed with double pole possibilities also available. Most limit switches are fitted with both a normally open and normally closed contact block.

Ingress Protection (IP rating)

Choose the ingress protection based on the installation environment: Environmental considerations such as ambient temperature, vibration and shock resistance, and protection class should also be taken into account when selecting a limit switch. Open type limit switches are typically rated to IP40 with enclosed types rated to IP65. IP67 limit switches available, typically supplied with a factory installed lead. You can learn more about IP ratings clicking here

Operating Frequency

Calculate the operating frequency, normally measured in activations per minute. If this operating frequency is exceeded, the limit switch may malfunction or be damaged.

Operating Force

Determine the force required for triggering the switch. Heavier duty switches will have operating forces in the hundreds of grams. Whereas small micro-switches will have operating forces in the low tens of grams only. Using a microswitch in a heavy duty environment will destroy the microswitch.

Service Life

The service life may be divided into machinery working life and electrical working life. The typical mechanical service life of limit switches is 10 million operations with the electrical service life being around 500,000 operations.

Switches Plus carry an extensive range of limit and micro switches. You can see our range here

Can't find what you need contact us and we will do our best to help you.

Our Limit Switches are manufactured in Taiwan by Moujen. You can download a catalogue here or visit their website here