Normally open (NO) & Normally close (NC) contacts Introduction

NO (normally open) & NC (normally close) contacts Introduction

Often you have found NO, NC & COM in the electrical circuits. Most of the electrical circuitry processes depends on “Normally open” & “Normally close” contact.

NO – Normally open contact.

NC – Normally close contact.

COM – Common contact for NO, NC.

For example we take a SPDT relay, which have two coil connections, 1 Common, 1 NO & 1 NC connection. We gives +12v on COM and relay coil is off mode, NC contact will have +12v also because it is normally connected to COM contact and NO contact will not have +12v because it’s normally disconnected to COM contact.

If we energize to relay coil, NO will be closed with COM contact and NC will disconnect to COM. If we talk about any push type switch, push action will same as active relay coil.

Where use NO & NC contacts

1. Electrical relay

 

2. Controller & PLC

3. Electrical Contactors

4. Switches

 5. Various types of measurement tools like pressure switches, Liquid level indication etc.