Johnson Electric - Sealed Microswitches

General Use Of Microswitches:
Microswitches have become indispensable in the sensing and control industry for controlling electrical signals. With years of experience, Johnson Electric has supplied billions of microswitches used in home appliances, industrial equipment, automotive applications, agricultural machinery, and control systems worldwide. In most applications, the requirements for the switches are quite simple: they consist of at least two contacts, a common contact with either a normally open contact or a normally closed contact, connected to a snap-action mechanism to switch between the contacts and turn devices on and off. While these switches can operate safely and reliably in general applications, they have limited capabilities in various harsh environments. For this reason, sealed microswitches emerged as a viable solution. Sealed microswitches are basically the same as un-sealed microswitches with the addition of a protection against dust or moisture to enter the switch and reach the contact system.

Microswitches in Home, Industrial, or Automotive Applications:
The requirements for switches, however, can be extremely demanding in environments with high humidity, such as certain household appliances (dishwashers, coffee machines, etc.) or in industrial and automotive applications. Besides water, oil and dust can have a major impact on the applications, sudden temperature changes can also affect the proper functioning. It requires a high degree of sealing to ensure that the switches work without any problems. For example, this sealing should not only withstand the standard temperature range of -40°C to +85°C, but also function at higher temperatures or unexpected temperature drops. These specific applications therefore require a balanced and customized solution in sealing technology, regarding materials, switch- and seal design.

Sealing Technology:
To achieve sealing against dust or water, a "flexible" membrane must be fitted on all switch parts that have an open connection between the internal mechanism of the switch and the outside world. Such parts may be the plunger, the housing parts, or the terminal outputs. In the case of the plunger, the membrane must be flexible; in other areas, a more rigid seal may be sufficient. Consequently, for the microswitch to be manufactured properly and to ensure its function for a long time in harsh environment, the choice of sealing materials is crucial. Adding a seal to a microswitch affects its operating characteristics. In the case of the plunger, adding a seal usually increases the operating force. On the terminals, the seal can limit the soldering time to prevent overheating.

To provide a high-quality seal, Johnson Electric uses either a seal ring mounted separately on the plunger or twin-shot technology to provide housing parts with built-in seals. Different technologies are used for the housing parts and terminals. For example, either by ultrasonic welding of housing parts or by applying a special glue. By applying these solutions, the microswitches can be qualified with the IP67 degree of protection. When open terminals are used, IP protection is limited to the top or plunger side.

Johnson Electric Offer:
Johnson Electric's qualified switches are used to accurately detect the position of mechanical components in industrial and household applications. Additionally, to ensure 360-degree protection of the microswitch, Johnson Electric offers the option of adding moisture protection on the terminal side with lead wires soldered to the switch terminals. These lead wires are then routed through a cable box and potted to ensure IP67 protection on the terminal side. If the switch is UL approved the wires must also be UL approved. The final microswitch product is an IP67-protected switch with an operating temperature range between -40°C and +85°C according to UL61058 and even up to +125°C on demand.

Sealed switches are available in a wide range of sizes and ratings. The most common series are L16, V4NS, F1NS, V3S, 4BR, V9N and TS sealed switch families. Except for the TS, all other switches can be supplied with regular levers or terminals. All mentioned switch families have a UL or/and ENEC approval.

Conclusion:
Johnson Electric can offer you a complete program of sealed switches. The features of these switches include compact size, high lifetime, a high level of protection, and increased electrical properties, etc. There are different types of microswitches, but their selection depends on the requirement. To support you with the correct switch selection please contact our sales department for more information.

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