Deep Drawing Forming Die For End Caps; Metal Stamping Die

I. Understanding the Basic Structure of a Micro Switch

A micro switch typically consists of a button, spring, and contacts. Its working principle is that pressing the button causes the contacts to close or open, thus controlling the circuit's on/off state. Before determining whether a switch is normally open or normally closed, we need to understand its structure.

II. Definitions of Normally Open and Normally Closed

Normally Open: When the button is not pressed, the contacts of the micro switch are in the open state; when the button is pressed, the contacts close, and the circuit is connected. Simply put, "no connection unless pressed, connection only when pressed."

Normally Closed: Conversely, when the button is not pressed, the contacts are in the closed state; when the button is pressed, the contacts open, and the circuit is disconnected. That is, "connection only when not pressed, connection only when pressed."

II. Determination Method

1. Observe the External Markings
Some micro switches will have markings indicating normally open (NO) or normally closed (NC) on their casing. 1. If your purchased microswitch has this marking, you can directly determine its orientation based on the marking. However, it's important to note that not all microswitches have clear visual markings.

2. Use a multimeter to measure. This is a more accurate method. Set the multimeter to the resistance range, and then touch the two probes to the two pins of the microswitch. When the button is not pressed, if the measured resistance is infinite, the contacts are open (normally open); if the measured resistance is close to zero, the contacts are closed (normally closed). After pressing the button, measure the resistance again and observe the change to further confirm the result.

3. Test with a practical circuit. If possible, you can connect the microswitch to a simple circuit for testing. For example, connect an LED in series with the microswitch and connect it to a suitable power supply. When the button is not pressed, if the LED lights up, the microswitch is normally closed; if the LED does not light up but lights up after the button is pressed, it is normally open.