Normally open (NC) contact concept.

Normally open (NC) contact concept.

This is PLC Program for NC contact.

Normally closed contact is known as NC contact. When the quantity has signal state 0, the NC contact allow signal flow and output result is 1.

When the quantity has signal state 1, the closed contact is not activated and therefore output state is zero.

If two NC contacts are connected in series, the power flows once all contacts have zero signal state.

If two NC contacts are connected in parallel connection, the power flows when one NC contact amongst all have zero signal state.

Example of the NC contacts.

In above example two NC contact are connected in series (tag 1 and tag 3). When both signal state are zero, output result is 1.

Motor ON/OFF application using on delay timer and ON delay timer application of the PLC.

Motor ON/OFF application using on delay timer and ON delay timer application of the PLC.

Problem Description

Motor ON/OFF application using on delay timer and on delay timer application of the PLC.

Problem Diagram

On delay timer means provide delay between two events. If we start any motor after some delay, we need to provide ON delay timer before motor.

We can provide physical ON delay timer or PLC timer for the motor. Take NO switch and connect timer and set the delay (5s ,10s etc.) and make the switch ON, after some delay motor will be ON.

In case of PLC, take NO contact for the switch and provide ON delay instruction between NO contact and output contact.

When NO contact signal state is 1, ON delay timer will be ON and after delay it will make output motor ON.