What are NO and NC? What is Normally Open or Closed Contact?

What are NO and NC, what do Normally Open and Normally Closed contact expressions mean? We will explain in detail with this blog post.

Before answering the question of what NO and NC are, it is necessary to look at the meanings of these concepts. NO and NC are abbreviations. They stand for Normally Open and Normally Closed, respectively.

 

These expressions often cause confusion. In fact, the reason is quite simple. For example, let's imagine that there is a power source and a LED fed by the source in a Normally Closed circuit. Since there is no open circuit on top of the circuit, meaning it is a closed circuit, the voltage from the power source reaches the LED and the LED lights up. So this circuit works. However, because the circuit is named closed, there is a perception as if the LED should not light up. This is a completely natural situation. Confusion arises entirely from this.

 

In an open circuit, since there is an open connection in the circuit, meaning the circuit is not complete, the energy from the power source cannot reach the LED. So the LED does not light up. You can find more detailed explanations for both circuit types in the continuation of the article.

 

Normally Open circuit (normally open) indicates that there is something in the mentioned electrical circuit that prevents the circuit from being completed.

 

 

As can be seen in the circuit example here, since the switch on the circuit is open, voltage does not reach the receiver. Therefore, the circuit is referred to as a normally open circuit.

 

Normally Closed circuit (normally closed) indicates that there is nothing in the mentioned electrical circuit that prevents the circuit from being completed.

 

 

As can be seen in the circuit example here, since the switch on the circuit is closed, voltage can reach the receiver. Therefore, the circuit is referred to as a normally closed circuit.