How to choose Omron micro switches?

1. Understand how the shape and scale of the switch affect other characteristics

The scale is important when choosing a micro switch. The switching scale is directly related to its characteristics, including current scale, stroke, and operating force. For example, the smallest microswitch on the market today measures 0.50" x 0.236" x 0.197" (LxWxH). While this tiny switch is suitable for detecting circuit status in compact circuit breakers, it typically only breaks 0.1 to 3 amperes (A) of current and has a short stroke.

Applications that require higher currents generally require larger switches. For example, in the case of fuel tanks, a micro switch used to detect the liquid level needs to be able to supply a large stroke and accept a large current. Generally, in the application of liquid level switches, the switches should directly drive the water pump and carry a large current. This requires a large micro switch with a current rating of 20A or 25A at 125VAC or 250VAC.

Tip: The smaller the switching scale, the smaller the stroke and the current that can be broken.

In addition, the size of the switch also affects the operating force. Ideally, engineers would need a switch with low operating force and high current capacity. But in fact, a compromise is required between these two parameters. In order to maintain a good touch while supplying a large current receiving scale, the micro switch requires a stronger spring, which will make the operating force and shape scale of the switch larger. Operating forces range from 2 grams in pressurized pneumatic applications to 8 ounces in solenoid valve applications that require higher operating forces. The largest switch on the market is 1.94" x 0.69" x 1.3" (LxWxH).

Engineers should also note the differential travel of the switch—the gap between the switch trip and reset directions. The thresholds vary depending on the application. For example, in the case of temperature switches, the on/off operating points should be as close as possible, and the differential travel should be as low as 0.0001 inches. However, in the application of liquid level pumps, too close differential stroke may lead to too frequent start and stop of the make-up pump, shortening the service life of the pump.

2. Understand your electrical requirements

Microswitches are typically capable of breaking currents from 5mA/5VDC to 25A/250VAC. The micro switch product line offers a wide range of products from low-energy consumption to power-loaded electrical types, suitable for a wide range of applications.

Engineers must know the current and voltage ratings (AC or DC) required for the specific application in order to select the appropriate switch. Since all types of equipment in all occupations are committed to low energy consumption, micro switches must be able to operate at low currents (logic level loads) and DC voltages.

However, there are also applications that require switching that can break high currents and high voltages, such as industrial pumps.

In addition to load requirements, engineers must also select the appropriate circuit. The switch contacts must be either normally open (NO) or normally closed (NC). In the case of NO-type contacts, in general, no current flows between the contacts. When the switch is actuated, the contacts are closed and the circuit is connected. In the case of NC type contacts, in general, there is an electric current passing between the contacts. When the switch is actuated, the contacts open and the circuit is disconnected.

3. Consider environmental conditions

Environmental requirements have a great influence on the selection of micro switches, especially in applications such as industrial control and medical equipment, which require high reliability and criticality. Understand the environmental conditions in which you operate, including the contaminants in the air that may enter the switch, the liquid in which the switch is located, and the operating temperature requirements.

When it comes to applications in harsh environmental conditions, you need to choose a sealed switch with a wide operating temperature range. The highly robust microswitches can operate in temperatures ranging from -65 degrees Fahrenheit (-54 degrees Celsius) to 350 degrees Fahrenheit (177 degrees Celsius), making it easy to handle a wide range of applications. Together, it should also be noted that the protection level of the switch should be at least IP67 to prevent liquid ingress. This eliminates the need to spend a lot of time designing an enclosure that achieves the same level of protection.

4. Clarify the requirements for the life of operation

The robustness of the switch is crucial. Do you need to know exactly how many times an electrical and mechanical operation is required? Different switches have different contact materials, housings and terminals to meet the electrical and mechanical life requirements of different applications.

A highly robust micro switch is capable of operating 10 million to 20 million times before mechanical failure and 50,000 to 100,000 times at maximum load before electrical failure.

As for the slim price difference between the different quality switches, you need to take into account the total cost of operation. Because you're not just paying for the switch, you're also paying for the long-term, trouble-free operation. In many cases, the nominal cost of a more robust switch is offset by the lower warranty cost over its lifetime.

5. Check the certification requirements of the organization

Selecting switches that meet a wide range of international electrical requirements can help you simplify your product design for different areas. Some of the primary regulatory certifications include UL certification in United States, cUL certification or CSA certification in Canada, ENEC certification in Europe, and CQC certification in China.

When choosing a microswitch, you need to consider a number of factors, such as form factor, load requirements, operating environment, and reliability, so it's important to understand the actual application requirements: What size of switch is needed? What is the power rating required? Is it a low-pressure application? Does the switch need to be sealed? Does the switch need to accept the pole temperature? Is there a need for certification from an international organization? Is it a critical application? Once these issues are understood, it is easier to choose the right switch for the application.

How to choose Omron micro switches?

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