Fretting switch in the selection of some insights, and in the current market so many brands, we must make more efforts in the selection, the following is Dongkun Electronics Technology Co., Ltd. Dongguan to do some introductions for you.
Since its inception in the 1930s, micro-switch has been continuously developed to meet various application requirements, including aerospace, household appliances, boiler control, medical equipment, spray system, test equipment, timers and vending machines. Fretting switch is usually used to detect temperature, position and liquid level.
Precision micro-switch usually has three specifications: basic type, with operating handle type, with operating handle and shell type. The micro switch is designed according to sincerity and spring.
Whether engineers are looking for temperature controllers for residential heating or industrial boiler control or liquid level switches for large oil tanks, they need to consider the following five key features: shape size, electrical requirements (voltage/current), reliability (mechanical/electrical life), environmental factors (dangerous environment, temperature range) and institutional certification. The following five key steps can help you choose the micro switch suitable for your specific application.
Step 1: Understand how the size of the switch affects other characteristics
Size is very important when choosing micro switch. Switch size is directly related to its characteristics, including current range, stroke and operating force. For example, the smallest micro-switch on the market today has a size of 0.50 inches x 0.236 inches x 0.197 inches (LxWxH). Although this tiny switch is suitable for detecting circuit states in compact circuit breakers, it usually cuts off only 0.1 to 3 amperes (A) of current and has a shorter trip.
Large switches are usually required for applications requiring larger currents. For example, in the application of fuel tank, the micro-switch used to detect liquid level needs to be able to provide large stroke and withstand large current. Usually in the application of liquid level switch, the switch should drive the pump directly and carry a large current. This requires a large microswitch with rated current of 20A or 25A at 125VAC or 250VAC voltage.
Tip: The smaller the size of the switch, the smaller the stroke and the current that can be interrupted.
In addition, the size of the switch also affects the operation force. Ideally, engineers need a switch with low operating power and high current capacity. But in fact there needs to be a compromise between the two parameters. In order to maintain good contact while providing a large current bearing range, the micro switch needs stronger spring, which will make the operation force and shape size of the switch larger. Operating force ranges from 2 grams in pressurized pneumatic applications to 8 ounces in solenoid valve applications (requiring greater operating force). The largest switch on the market is 1.94 inches x 0.69 inches x 1.3 inches (LxWxH).
Engineers should also pay attention to the differential stroke of the switch - the distance between the switch tripping position and the reset position. Its threshold varies according to different applications. For example, in the application of temperature switches, the on/off operating point should be as close as possible and the differential stroke should be as low as 0.0001 inches. However, in the application of liquid level pump, too close differential stroke may lead to too frequent start-up and shutdown of the water supply pump, shortening the service life of the pump.
Photo Description: Honeywell's MICRO SWITCH? Micro switch has a variety of configurations to choose from.
Be able to meet the specific needs of engineers.
Step 2: Understand your electrical requirements
Fretting switches can usually cut off the current from 5mA/5VDC to 25A/250VAC. The micro switch product line provides a range of products from low energy consumption to power load electrical type, which are suitable for various applications.
Engineers must know the rated current and voltage (AC or DC) required for specific applications in order to select the appropriate switch. Because all kinds of equipment in all industries are dedicated to low energy consumption, micro-switch must be able to work under low current (logic level load) and DC voltage.
However, there are also some applications that require switches that can cut off large currents and high voltages, such as industrial pump applications.
In addition to load requirements, engineers have to choose the right circuit. Switch contacts must be one of the constant open type (NO) and the normal closed type (NC). For NO contacts, there is usually no current passing between the contacts. When the switch operates, the contacts are closed and the circuit is connected. For NC contacts, currents usually pass between contacts. When the switch operates, the contact opens and the circuit is disconnected.
Step 3: Consider environmental conditions
Environmental requirements have a great impact on the selection of micro-switch, especially in high reliability and critical applications such as industrial control, medical equipment and so on. Understand the application of environmental conditions, including air pollutants that may enter the switch, the liquid in which the switch is located, and operating temperature requirements.
For applications in harsh environments, you need to choose a sealed switch with a wide operating temperature range. High reliable micro switch can work in the temperature range of - 65 (- 54 Celsius) to 350 (- 177 Celsius) and can easily handle various applications. At the same time, it should be noted that the protection level of the switch should be at least IP67 to prevent liquid intrusion. In this way, it is not necessary to spend a lot of time to design a shell that can achieve the same level of protection.
Step 4: Define service life requirements
The reliability of the switch is critical. You need to specify how many electrical and mechanical operations are required for an application.
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