A limit switch is an electromechanical device, and it can be considered as a contact sensor that is widely used in many industries to detect the position or presence of an object. This device has good precision and repeatability and it is because these switches make direct contact. So these switches are used in many industries and they can be seen at the end of the mobile element such as a conveyor belt. This switch is capable to detect the presence or movement of an object, it can also determine the passing and end of travel of the object. The limit switch has an actuator so when the device is in contact with the actuator, then the contacts will be operated by the switch so that it can create or break an electrical connection.
What is the need for a limit switch?
These switches are widely used and they are used in many applications because it is very easy to install and they are reliable too. It can also detect the presence of an object or its passing. The position of an object can also be determined by using a limit switch. These switches have a high current capacity, this switch also has good precision, snap action operators and it can provide accurate operations. These switches are small in size so it can be used where space is a constraint.
How does a limit switch work?
When the object comes in contact with the actuator of the limit switch, then the actuator will move and it will move inside the limit switch. This actuator will be linked to a set of contacts. The position of the contact will be changed if the actuator lever is pressed by an object. So if a device has made a contact with the actuator then the contacts in the limit switch would make or break the electrical connection.
What are the components of the limit switch?
The major components in the limit switch are actuator, head, contact, terminal block, switch body, and base.
- Actuator – It is the part of the switch which will be in contact with the object that is being sensed
- Head – this part acts as a covering for the process in which the actuator movement is converted into contact movement
- Contact block – this part act as a housing for the electrical contact elements of the switch
- Terminal block – In this part, the electrical connection between the switch and the control circuit is done.
- Switch body – this part would house the contact block in a plug-in switch and the terminal block in a non-plug-in switch
- Base – the purpose of the base is to house the terminal block in a plug-in-switch, there is no separate base for a non-plug-in switch
How to select a limit switch?
- The electrical rating of the limit switch must match the system, in which it is installed
- These switches are available according to a variety of body and operating requirements so select according to your need
- We must consider environmental factors such as vibration, moisture, etc.
- It must be selected according to the required operating force and reset force
- It must be selected according to the over-travel and pre-travel
What are the types of limit switches?
Snap switch
The snap switch would trigger so quickly when the actuator moves, these switches can also work without an operator and these switches are mostly used for applications that require basic contact, these devices are used to detect short movements.
Gravity return
This type of limit switch is mostly used for the production line and also used for conveyor operations. The operation of this type of limit switch is depended on gravity, its contact switches are reset by using gravity and it is done by exerting force on the arm of the lever.
Miniature enclosed reed
This limit switch is really small and it costs very less and die-cast zinc is used to create it. This limit switch has a sealed reed contact and because of this it is capable of high contact reliability and it can also be used where environmental stress is high.
How to connect the limit switch to a CNC system
By using access lugs we can connect the wires from the limits witch to the computer and from there the CNC software can perform according to switch trips.
What are the advantages of a limit switch?
- It is very easy to install
- It can operate at high voltages
- It is not affected by static electricity because it doesn’t have magnets
- Good accuracy and repeatability
- Housing is durable
- It provides high resistance to different ambient conditions that are found in an industry
- It can be used to switch high power loads
- It provides immunity to electrical noise interference
- It doesn’t have any leakage current and the voltage drop is very low
What are the disadvantages of a limit switch?
- Contact life is less
- The mechanical parts would wear-out during time
- Contact sensing cannot be used for most of the applications
What are the applications of a limit switch?
- It can be used in high-speed production equipment
- It is used in automatic control circuits
- Elevators
- Conveyors
- Cranes
- It is also used in milling and boring machines
- It is used in pumping systems to control the liquid level
