1.What is the Limit Switch?
A limit switch is a type of switch used to limit the movement of certain moving parts in a structure or a system. It is structured like a normal electrical switch, still has the function of opening and closing, but there is an additional need for impacting for moving parts to change the state of the contact inside it.
The purpose of the limit switch is to convert mechanical movements into electrical signals.
One feature of this type of device is that it does not save status. That means when it no longer works, it will return to the original state.
A common example is the limit switch installed in the refrigerator, when opening the door, lights up, when the door is closed, the light goes out.
2. Structure of Limit Switch
Normally, a stroke switch will be made up of 3 main parts:
- Transmission unit: this is a fairly important part of a stroke switch, which makes the difference between them and other types of switches. They are mounted on the top of the switch that receives the action from moving parts to activate the switch.
- Switch body: the body of the switch will consist of internal components with a plastic (or iron) casing, protecting the internal circuits from physical impact agents.
- Connection terminal: this is considered as an output signal for the switch because it is responsible for transmitting signals to other devices when affected by the transmission unit.
3. The working principle of Limit Switch
In principle, the operation of the stroke switch is quite simple. Usually a switch will have the following operating parts: levers, COM, normally closed (NC) and normally open (NO) pins. In normal state, there is no effect to the transmission part of the switch, the contact between COM pin and NC pin will be matched. But when there is an impact on the actuator will cause the COM pin NC pin to split later and the COM pin will act on the NO pin. This will activate the operating status and control the output signal of the switch.
4. Limit Switch Classification
Currently on the market there are many different types of travel switches. Each type will have its own advantages and disadvantages depending on the needs and scope that we use. However, in this article plc247.com will only classify according to the commonly used formats on the market. If divided according to the outer shape, we have the following forms:
+ Wheel type limit switch
It is a plastic body type limit switch, IP65 standard, one-way impact type, capable of operating with a voltage of 500VAC, rated current up to 10A, with a contact of 1 NO and 1 NC.
+ Wheel type limit switch with lever
The limit switch has a body and wheel (roller level) is designed plastic body, IP67 waterproof standard, operating temperature at 70 degrees C, works with a maximum voltage of 500VAC, rated current 1A, go comes with NO and NC quick-acting contacts, with a two-way lever.
+ Metal body type limit switch
Limited switch version with a body made of metal, IP66 waterproof standards, the design needs impact can increase or decrease the length of flexible with two-way action. Operate with voltage up to 500VAC, 10A with voltage 24VDC, operating temperature -25 > 70 ‘C, Contact 1NO + 1NC release impact type
+ Limit pull type limit switch
A type of switch that works by pulling up through a metal ring on the top, used in emergency systems, or in sliding door applications, metal body design, IP65 watertight standards, contact points fast NO, NC 10A, voltage 500VAC, Operation cycle 3600 times an hour.
+ Limit switch type spring
Design switch with two versions of plastic body and metal body, for plastic body, it reaches IP65, metal body reaches IP66. In general, both types can be used outdoors very well.
1NO + 1NC contact type fast acting. The difference between this type of switch and other types is that there is a spring on the head that receives the impact from the transmission.
+ Other limit switches
Besides, there are many different types of journeys on the market, with different input impact structures and different parameters, structure, scope of activities and applications. And because plc247.com’s knowledge is limited, it will not be able to list more fully for you.
4. Advantages and disadvantages of limit switches
Each type of switch will have different advantages and disadvantages, but overall, a journey switch will have strengths and weaknesses that we need to be concerned about. This is useful in equipment and investment for production lines or production support devices, in particular, they have the following advantages and disadvantages:
Advantages:
- Consume less electric power
- Usable in most industrial applications
- Can control multiple loads
- Good response to conditions that require strange accuracy and repeatability
Disadvantages:
- Limited to devices with relatively low movement speeds
- Must be in direct contact with the device
- Due to contact, the mechanical parts are worn out
5. Application of limit switches
Limit switches are used a lot and are popular in both industrial and residential applications, helping to detect:
- Detect contact of object
- Count
- Motion range detection
- Detect position and limit motion
- Circuit breaker when having trouble
- Speed detection
With the advantages of ease of use, high accuracy and high convenience, the travel switches are used a lot. There are things that we encounter every day that use a cruise switch without realizing it:
- Limit switches used in refrigerators
- Limit switches used in rolling doors
- Limit switches used in elevators
- Limit switches for industrial use
In factories, this switch is used a lot like: on the production line, conveyor belt, conveyor belt …
Through this article plc247.com hope you can better understand what a switch is and the knowledge related to it. Hopefully, with the above sharing, help you somewhat supplement your knowledge. The article certainly has many shortcomings, you can contribute more comments by commenting below
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