How to Replace a Linear Actuator Micro Limit Switch

Linear Actuator Micro Limit Switch

If you have some mechanical experience, you might know about linear actuators. If not, these are devices that create a movement along a straight line.

Manufacturers often include actuators in pneumatic or hydraulic machinery, and they can be either electrical or mechanical. Though linear actuators can be large enough to operate a swing boom crane, a small linear actuator can fit inside little nooks and tight spaces.

The actuator is a crucial component of limit switches or micro limit switches for the smaller variety. Here, we take a closer look at the switches for a small linear actuator and see how to replace them under various conditions.

What Are Limit Switches?

A limit switch is an electromechanical device that detects the presence or absence of an object. The purpose of the component is to create an endpoint an item can travel before it stops. The switches can also monitor an object’s movement limits and indicate if it has exceeded its limitations.

How Do Limit Switches Work?

Standard limit switches consist of a mechanical actuator with connections to multiple electrical contacts. When the object or target touches the actuator, the component’s plunger’s movement causes the contacts inside the switch to close its electrical connection for a normally open circuit. Likewise, it can open the connection for a normally closed circuit.

The limit switch controls or alters the state of the electrical switch with the actuator plunger’s movement. Unlike photoelectric, inductive, or capacitive proximity sensors that can perform the same function without making direct contact with a target, a limit switch requires a connection. Most limit switches have a mechanical operation, and their electrical contacts alternate between higher currents than proximity sensors.

Micro Limit Switches

A micro limit switch is a type of limit switch you can usually find on control circuits. They are much smaller than the standard variety, resulting in the need for a small linear actuator. Ideally, you can install micro switches in narrow spaces that other models could not fit inside.

The micro switch has two components operating on one terminal. One switch is to open the current (normally closed) and one to close it (normally opened). The technical configuration for the switch is Single Pole Double Throw or SPDT.

Most micro switch limit switches contain an actuating plunger near its top that travels a small distance to make contact with the target and trigger the electrical contacts to open or close. The switch will depress the plunger for a predetermined number of times before it starts an action.

It’s possible to change the micro switch’s contact positions because they allow for a small degree of movement. Also, a spring-loaded mechanism allows the contacts to snap into different places as needed.

Micro switch designs include a range of activating arms and electrical connections of around 250 volts of alternating current. They often have fixing holes for users to mount them to a fixed surface quickly.

Types of Limit Switches

Limit switches typically fall into one of these four categories.

Whisker

These sensors operate similarly to animal whiskers, hence the name. The guitar string sensor attached to the head of the switch can detect nearby objects within its environment. When something disturbs the sensor, it sends a pulse to the switch to either stop and retract the actuator or stop and extend it.

You can find these micro switches in robotics or within assembly lines.

Roller

Bin filling and conveyor systems often include roller limit switches within their operations. The plunger has a roller operating head that can perform a horizontal or vertical motion to trigger the limit switch. Most roller switches include cams or rotating wheel bumps that actuate the switch contacts when the cam touches the roller.

Lever

This limit switch uses a physical lever to operate an electrical switch to perform a simple on and off function. The level or toggle can move back and forth to activate or deactivate the limit switch by allowing its electrical contact points to touch together and complete the circuit.

Lever limit switches can range in size to control mechanical functions, but they are usually large and can control anything from turn signal to cruise control in vintage cars with modern amenities.

Plunger

Plunger limit switches work by pushing down on the linear actuator with rollers, pushbuttons, or pins. They are ideal for products with small spaces, and you can typically find them on assembly line operations.

Snap Action Micro Switch

The most common type of micro limit switch is the snap action variety. It uses an actuating lever to create a fast switch with minimal pressure on the actuator. It’s sufficient enough to produce at least a million operations, and you can find them in lamps, motors, and pressure switches.

Applications for Various Micro Limit Switches

You can find uses for these switches throughout various aspects of everyday life, including industrial equipment, consumer devices, building automation, and security applications. Their design requires them to be sensitive to pressure changes and movement, making them common in equipment that requires precise movements or measurements. These switches can also detect temperature.

Here are some of the practical applications for micro switches:

  • Microwaves: Manufacturers often include micro switches in devices, like microwaves, that use interlocking doors. For microwaves, a user must close the appliance’s door before they can turn it on.
  • Elevators: Micro switches are inside elevator doors to act as a safety switch.
  • Copiers and Printers: The device can detect when paper jams a copier or printer and signal the machine to stop until someone removes the clog.
  • Vending Machines: A switch can act as a leveling device to help vending machines disperse goods to consumers.
  • Washer and Dryer Machines: The switches in these appliances detect when the doors are open or closed so that the machine can turn off or on, respectively.

Other applications for these devices include:

  • Access control panels
  • HVAC units
  • Micro robotic applications
  • Timer controls
  • Turning mechanisms on surveillance cameras

How to Replace Small Linear Actuator Micro Limit Switch

These switches are simple, inexpensive, and generally require no maintenance during their long lifespan. Some models can last up to 10 million cycles.

However, if you need to replace a small linear actuator micro limit switch that isn’t functioning correctly, you can dismantle the device’s mounts and install a new one that fits your specifications.

It is worth noting that sometimes you may need to adjust the linear actuator’s stroke length to stop it before it fully retracts or extends and not replace the entire device. Because of a small linear actuator’s size, it may have an end-switch to cut the device’s power when it hits the end of its stroke in either direction or have an adjustable limit switch at all.

If the actuator doesn’t have the means to stop its power at the end of its stroke, the device can sustain damage as it burns out its motor and wears down its physical components.

External Limit Switch Kits for Linear Actuators

For linear actuators without a means to prevent damage to themselves from overworking, you can install an external limit switch kit to keep the device from burning out.

The limit switch kit consists of two switches with an external mount to connect to a control circuit to operate the actuator. You can adjust your actuator’s stroke with the equipment as long as any moving part of the mechanism makes contact with the switch, whether it’s a rod, block, or the actuator.

To install a small linear actuator limit switch kit, you will need:

  • A small linear actuator
  • An external limit switch kit
  • A power source
  • Your choice of a control switch
  • Wire stripper
  • Soldering iron or crimp connectors
  • Heat shrink tubing (for soldering connections only)

Connecting the external limit switch kit to the linear actuator is a simple process. To begin:

  1. Mount the external limit switches within the desired parameters for your actuator.
  2. Connect the control panel to the power source.
  3. Retract the actuator until the tip of the actuator is within these parameters.
  4. Connect the external limit switch to the ground cable within the kit. You can find this point between the linear actuator and the control source. Solder connections in place, if you wish, or use crimp connectors to prevent unintentional movement.
  5. Test the linear actuator’s movement to ensure that it retracts and extends when it touches the limit switches and doesn’t move farther than those parameters.

Looking for a Small Linear Actuator? Contact Us Today

A small linear actuator and limit micro switch have an abundance of everyday uses, whether you’re working with robotics, household appliances, building automation, or industrial devices.

If you would like more information about these devices or know what type of actuator you need, contact our Creative Motion Control team. Our team of expert technicians, researchers, and engineers make the best linear motion products on the market. To speak with a team member about your needs or request a quote, call (425) 800-8045 today.

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