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A limit switch is an automatic sensor assembly that requires direct physical contact to detect the position of an object or material. Read on to learn more about limit switches.
A limit switch is an automatic sensor assembly that requires direct physical contact to detect the position of an object or material. It is typically used to monitor the presence/absence, proximity, and/or movement of items or materials within a system. Depending on the detected condition, the actuator opens or closes electrical contacts, automatically stopping or starting the flow of electricity to the connected device. This feature makes limit switches ideal for applications where tight restrictions must be adhered to.
What Is a Non-contact Magnetic Limit Switch?
Non-contact magnetic switches are similar to traditional limit switches but have the added advantage of operating without physical contact between the switch and actuator. This additional feature makes contactless magnetic switches perform better in harsh or dirty environments and are more difficult to cover. Non-contact magnetic limit switches also have a longer service life, reducing potential downtime for equipment repairs.
How Do Limit Switches Work?
The original purpose of a limit switch is to monitor the movement of an object or material within a system and stop its progress within preset limits without direct human intervention. They perform this function via an actuator that breaks the electrical connection when an object or material comes into contact with it. This stops the operation of the equipment and thus the movement of the load.
In other applications, a limit switch may establish an electrical connection when an object or material comes into contact with it. This activates the connected device or system, allowing it to perform necessary functions depending on the situation.
Components of Limit Switch
A standard limit switch consists of an actuator with an operating head, a switch body, and electrical terminals.
- The operating head transmits the linear or rotational force generated by contact with the triggering object to the actuator.
- An actuator opens or closes a switch in response to the application or removal of force.
- The switch body contains the switch contact mechanism, which opens or closes the connection between the electrical terminals.
- Electrical terminals connect the switch to the circuit it controls.
Industrial applications often require highly durable and reliable switches that can withstand heavy use without compromising accuracy. Limit switches can be customized to meet the needs of specific equipment and operations. By adjusting your switch's size, mounting, stroke frequency, electrical rating, and operating force, you can ensure reliable, safe operation of your equipment, even in harsh industrial conditions.
Types of Limit Switches
There are many types of limit switches, each with unique characteristics and suitable for different uses and environments. Based on the operating head design and driving method, they can be divided into four categories:
- Non-Contact Magnetic Limit Switches: Non-contact magnetic limit switches are highly responsive switches that are controlled using magnetic actuators on moving parts of the equipment (i.e. doors, gates, pistons). The switch is triggered when the actuator comes close to it. The switch can then electrically trigger an alarm, shutdown, etc. Non-contact magnetic limit switches have fast response times, making them an excellent choice for applications such as door switches, elevators, light switches, lifts, conveyor belts, pressure switches, and temperature switches.
- Whisker Limit Switch: A whisker limit switch has a long, flexible spring arm (i.e., a whisker) that flexes when actuation force is applied and springs back to its normal position when removed. Commonly used in conveyor and assembly line applications, they can monitor the flow and placement of materials and sound alarms if items are misplaced.
- Roller Limit Switches: Roller limit switches use rollers on a fixed axis to measure material flow or the number of items moving through a production line or conveyor. They measure the number of items, volume, or flow rate based on the number of drum revolutions.
- Lever Limit Switches: Lever limit switches are highly responsive switches that are controlled using a lever mounted on a rotating shaft. This lever allows movement to continue to preset limits. Once the lever pivots to its extreme point, the switch opens the circuit, triggering an alarm or shutting down. Lever limit switches have a very fast response time, which makes them ideal for use in door-opening indicators, elevators, lifts, conveyors, pressure switches, and temperature switches.
- Plunger Limit Switch: Plunger switches are equipped with a plunger that requires less physical effort to activate the plunger than other limit switches. The plunger is connected to a spring and electrical contacts to open or close a circuit when pressed. They are ideal for filling and conveyor applications that require fast response times.
Limit switches can also have designs that combine features of two of the four types mentioned above.
Applications and Uses of Limit Switches
Limit switches are incorporated into a variety of flow control, conveying, and sensing applications. They are durable, versatile, and accurate, available in a variety of designs, mounting systems, and sizes to meet the most stringent specifications. Some of the most common applications for limit switches include:
- Conveyors: Limit switches are used to monitor and control the position, speed, and quantity of materials and objects in conveyor applications.
- Assembly Line: Assembly lines use limit switches to monitor and control the location, location, quantity, and speed of components on the assembly line.
- Magnetic Control Circuit: Limit switches are used in electric motors to control start, stop, acceleration, and deceleration operations.
- Emergency Systems: Limit switches are used to notify operators of equipment malfunctions, overloads, temperature fluctuations, extreme pressures, housing openings, and other conditions that may affect operational safety.
- Appliance Lights: Limit switches are integrated into ovens, refrigerators, microwaves, and other household appliances and activate the lights when you open the door.
- Automotive Systems: Limit switches are used to turn on the interior lights when the door is opened. They are also incorporated into automobile manufacturing and assembly equipment.
- Counting Operations: Limit switches are used to count the number of products on conveyors in production, assembly, packaging, and other industrial and manufacturing operations.
- Filling Stations: For operations using buckets, baskets, boxes, and other containers, limit switches are used to automatically detect when a container is full for faster, more accurate filling operations.
UG Limit Switch
The UG series limit switches feature high-quality, easy-to-use multi-option switch boxes for rotary actuators. Our limit switches enable stable and reliable remote control operation in a compact and rugged design. Its die-cast aluminum housing is powder-coated for corrosion resistance and features an on/off visual indicator, a quick-setting cam, and an easy-to-operate terminal strip. Offering a wide range of switch, sensor, and transmitter options, these economical switch boxes can handle most applications and provide clear identification even in quite harsh and hazardous environments, as the explosion-proof and weatherproof design meets a variety of location monitoring needs.
UG is a professional custom valve actuators and accessories manufacturer. We leverage our engineering expertise and industry experience to continuously improve our products and strive to provide efficient solutions and competitive pricing. UG is also a global supplier of engineered actuators and accessories to the oil and gas, mining, chemical, pharmaceutical, water and power, food and beverage, and general industrial markets. If you want to purchase actuators and accessories, please contact us.