Five key steps of selecting the micro switch

Microswitch, which is a small electromechanical switch since the advent of the 1930s, continuously development to meet the requirements of different applications, including aerospace, household appliances, boiler control, medical equipment, spray system, test equipment, timer and vending machines and other. Micro switch is usually used to detect temperature, position and liquid level.

The precision of the micro switch usually has three kinds of specifications: basic type, with a handle type, with a handle and shell type. The micro switch is used in pressing and spring design.

Engineers have to look at the control of residential heating or industrial boiler temperature control device, or applied to a large tank of liquid level switch, all need to consider the following 5 key features: appearance size, electrical requirements (voltage / current), reliability (mechanical / electrical life), environmental factors (hazardous environment, temperature range) and institutional certification. The following 5 key steps can help you choose the micro switch for your specific application.

Step 1: understanding the size of the switch is how to affect other properties of

Select the size of the micro switch is very important. The switch size is directly related to its characteristics, including current range, travel and operating force. For example, the current market size of a micro switch is 0.50 inches x 0.236 inch x 0.197 inch (LxWxH). Although this tiny switch is suitable for detecting circuit states in compact circuit breakers, it can only be divided into 0.1 to 3 AMP (A) current, and the stroke is shorter.

Larger switches are required for larger current applications. For example, in the application of the fuel tank, the micro switch for detecting the level of the liquid level is required to provide a large stroke and withstand high current. Usually in the application of liquid level switch, switch to direct drive pump and carry large current. This requires a large micro switch with a rated current of 20A or 25A at 125VAC or 250VAC.

Tip: the smaller the switch size, the smaller the stroke and the ability to break the current.

In addition, the shape of the switch is also affected by the operating force. Ideally, engineers need a switch with a low operating force and a high current capacity. But in fact there is a tradeoff between these two parameters. At the same time to provide large current range of the same time to maintain good contact, the micro switch will require stronger spring, and this will make the operation of the switch and the size of the big change. Operating force range can be from 2 grams of the application of the pressurized pneumatic type, to the application of the solenoid valve (need for a greater force) in the 8 ounces. The largest switch in the market size is 1.94 inches x 0.69 inch x 1.3 inch (LxWxH).

Engineers also should notice the distance between the switch's differential travel, the trip position and the reset position. Its threshold value according to different application will be different. For example, in the application of temperature switch, on / off the operating point should be as close as possible, the differential trip should be as low as 0.0001 inches. But in the application of liquid level pump, the differential travel is too close, which may cause the pump to be too frequent and shorten the service life of the pump.

Caption: Honeywell MICRO SWITCH micro switch has a variety of configuration options,
Able to meet the specific needs of engineers.

Step 2: know your
The micro switch is usually capable of breaking current from 5mA/5VDC to 25A/250VAC. The micro switch product line provides a series of electrical products from low energy consumption to power load. It is suitable for various applications.

Engineers must be aware of the specific application of the required rated current and voltage (AC or DC), in order to select the appropriate switch. Since all industries are dedicated to low energy consumption, the micro switch must be able to work under low current (logic level load) and DC voltage.

However, there are also some applications that need to be able to break the high current and high voltage switch, such as industrial grade pump applications.

In addition to the load requirements, engineers must also select the appropriate circuit. The switch contact must be one of the normally open (NO) and normally closed (NC). For the NO type contact, there is usually no current passing through the contact. When the switch is off, the contact is closed and the circuit is connected. For NC type contact, there is usually a current through the contact. When the switch is open, the contact is opened and the circuit is disconnected.

Step 3: consider the environmental conditions of

Environmental requirements for the choice of the micro switch, especially in the industrial control, medical equipment and other requirements of high reliability and critical applications. Understanding of the application of environmental conditions, including the air may enter the switch of pollutants, the switch is located in the liquid as well as working temperature requirements, etc..

You need to choose a wide operating temperature range seal type switch for the use of harsh environmental conditions. High reliability of the micro switch can be in -65 degrees Fahrenheit (-54 degrees Celsius) to 350 degrees F (177 degrees C) temperature range, can easily cope with a variety of applications. At the same time, but also pay attention to the protection level of the switch should be at least IP67 level, to prevent the liquid intrusion. This will not have to spend a lot of time to design a shell that can reach the same level of protection.

Step 4: clear work life

The reliability of the switch is very important. You need to clear an application in the end how many times the electrical and mechanical operating life of different switches with different contact materials, shell and terminals, can meet the different applications of electrical and Mechanical