How to Program PLC Interlocking Program?

Interlocking in general is called protocol action. It means defined bunch action to be taken when certain conditions occur. In a view of PLC, Interlocking is an action that is defined in the PLC program to control the process when certain conditions occur f.e. temprature exceeding its limit, flow below requirement or any parameter exceeding beyond its safe operating limits.

The PLC interlock program and the relay (contactor) hardware interlock have the same logic function, that is, B cannot act when A acts, and A cannot act when B acts.

Differences between PLC and Relay

Do you know how to program the PLC interlocking program? Follwing the steps below and you will program it quickly.

• Establish external input I0.01 and output virtual intermediate relay W0.01, when I0.01 triggered externally, the intermediate relay W0.01 has output.
• Establish external input I0.02 and output virtual intermediate relay W0.02, at this time, the two procedures do not interfere with each other.
• Establish a virtual normally closed contact of W0.01 in series with the W0.02 program, the virtual normally closed xontact of W0.02 is also eatablished in series with the W0.01 program.
• Compile, and then simulation, set I0.01 to ON, W0.01 has output, and W0.01 normally closed contact is open. At this time I0.02 is turn ON, and the "current" cannot reach W0.02 through the normally closed contact of W0.01.
• Reset 10.01 & I0.02, trun I0.02 ON, W0.02 has output, and W0.02 normally closed contact is open. At this tiem, I0.01 is turned ON, and the "current" cannot pass through the W0.02 normally closed contact.

If you want to see more details about how to program PLC interlocking program, see the video below.