How To Distinguish The Function Of The Terminal Of Micro Switch

Micro switches typically have three terminals labeled as Common (COM), Normally Open (NO), and Normally Closed (NC). These terminals serve different functions in electrical circuits, allowing the micro switch to control and sense the state of devices or systems based on mechanical actuation. Here's how you can distinguish the function of each terminal:

Understanding Terminal Functions:

Common (COM):

Function: The Common terminal serves as the central connection point within the micro switch.

Usage: It is typically connected to the power supply or ground in the circuit, depending on the specific application's wiring configuration.

Role: The COM terminal provides a pathway for current flow that can be interrupted or allowed based on the micro switch's actuation state.

Normally Open (NO):

Function: The Normally Open terminal is connected to the Common terminal when the micro switch is in its default state (unactuated).

Usage: It is used to control devices or circuits that should be activated or powered when the micro switch is actuated.

Role: When the micro switch actuates (by pressing the actuator or triggering the mechanism), the connection between NO and COM closes, allowing current to flow through the circuit and activate the connected device or system.

Normally Closed (NC):

Function: The Normally Closed terminal is connected to the Common terminal when the micro switch is in its default state (unactuated).

Usage: It is used to control devices or circuits that should be deactivated or interrupted when the micro switch is actuated.

Role: In its default state, the connection between NC and COM is closed, allowing current to flow through the circuit and maintain the operation of the connected device. When the micro switch actuates, the connection between NC and COM opens, interrupting the current flow and deactivating the device or system.

Distinguishing the Terminals:

To distinguish the function of each terminal on a micro switch:

Labeling: Micro switches typically have labels or markings near each terminal indicating their function (COM, NO, NC). These labels help identify which terminal serves which role in the circuit.

Physical Configuration: Physically, the terminals on a micro switch may be arranged in a specific order or configuration that corresponds to their function. COM is often centrally located, with NO and NC positioned on either side or in a specific arrangement depending on the manufacturer's design.

Electrical Testing: Use a multimeter to test continuity or resistance between terminals. In the default (unactuated) state, there should be continuity between COM and either NO or NC, depending on the switch type. Actuating the switch should change the continuity pattern, confirming the switch's operation and terminal functions.

Understanding and correctly identifying the function of each terminal on a micro switch is essential for proper installation and integration into electrical circuits. This knowledge ensures that the switch operates as intended, providing reliable control and sensing capabilities based on mechanical actuation.