What are the uses and types of Limit Switch?

You’ve probably heard of the term ’limit switch’’ if your work deals with electrical machinery. It is a piece of electromagnetic equipment that has an actuator having a series of contacts. It regulates machine operations having moving parts with a connection to a switching action mechanism.

The contacts permit the limit switch to sense the presence or absence of an object or material. Based on the detection of contact defects, an actuator is moved by the sensor that changes the condition of an electrical circuit. This movement shows that some set ‘limit’ has been achieved.

Domestically, limit switches are used in the home. Imagine these simple applications:

1- What makes the microwave stop whenever you open its door before the timer ends?
2- Alternatively, what keeps it from starting before shutting the door?
3- What makes the washing machine stop when the load is unbalanced?
4- Why does the dome lights in your car light up when you open the door?
5- What turns the light of the refrigerator on whenever you open the door or off whenever you close it?

These are non-industrial, home-based uses of limit switch in the home and place of work.

Different Uses of Limit Switch

Within the industries, limit switches are used in some industrial applications. Some of the cases of its usage are in packaging, food and beverages and fire safety.

1- Packaging

Stationery boxes approach the end of the packaging line, set to be piled on pallets ten boxes high. A suction-cup gripper palletizer picks a box swinging it to a waiting pallet. How does the unit stops when it reaches ten layers of boxes?

The pivot arm reaches the top of the vertical travel, and the hook hits a limit switch. The switch then signals the system to put the pallet down to resume the process.

2- Works in Dangerous Places

Logs are quickly reduced in a sawmill to construction beams by a high-speed saw. This production process makes the environment dusty from wood chips and dust making breathing impossible without personal protective equipment as a mask. An inspection would be impossible even with the use of goggles. So, a production department can devise an inspection system by using limit switches. Remotely, an operator configures the switches to be cut in the desired dimensions.

3- Fire Safety

In some buildings such as banks, or tall buildings, rooms are usually quickly closed in case of a fire incident. These doors move fast at a speed that will destroy itself without the use of limit switches. It slows it down before it’s fully opened or closed.

Types of Limit Switches

There are different types of limit switches depending on operation requirements, rotary arm styles, and environmental factors. Other factors you can use to select a limit switch is the reset force, operation force, pre-travel, over-travel and safety needs.

There are four significant types of limit switches as discussed below.

1- Global Limit Switch

They have a variety of actuators, terminations, electrical specifications, seal ratings, and circuitry. You will find the global limit switch in injection molding machinery, escalators, elevators and moving stairs, textile and packaging equipment, electronic assembly equipment, industrial doors and so on.

2- Medium-duty Limit Switch

They have a variety of actuators, terminations, sealing ratings and circuitry. You can find medium duty limit switches in overhead cranes and hoists, stamping machines, textile machinery, conveyors and farm machinery.

3- Heavy-duty Limit Switch

Epoxy-coated for protection, they have a die-cast body. This limit switch has a variety of mounting and actuator options. They can be used in the presence or absence in harsh environments such as power generating plants, welding and food, and beverage industries.

4- Safety Locking and Unlocking Style

This limit switch protects people and equipment by determining the position of moving components. You can find Safety limit switches in the following places:

• Hinged guards
• Cable-operated emergency stop
• Key-operated interlock and
• Solenoid locking

Benefits of Limit Switches

Limit switches offer several benefits. It serves the following purposes by:

1- Controlling multiple loads
2- Switching high inductance loads
3- Uses little electrical energy
4- Can be applied in almost all industrial environments
5- Their repeatability and accuracy is very high