PLC Program to Reset all Non-Retentive Outputs

This is a PLC Program to Reset all Non-Retentive Outputs.

Problem Description

Reset all Non-Retentive outputs of a process. Implement this by using MCR instruction in PLC using Ladder Diagram programming language.

Problem Solution
  • By using Master Control Relay MCR instruction, we can solve this problem.
  • When this instruction is enable, line is energized, it turns on.
  • When MCR is OFF, the number of following ladder diagram lines specified are turned off.
  • In many PLCs, all outputs are turned off while in many PLCs, only Non-retentive outputs are turned off.
  • In PLCs such Allen Bradley and Siemens, all non-retentive outputs are turned off.
  • The MCR must be turned on to be inactive. If the function goes off for some reason, it is active and turns the specified lines off.
PLC Program

Here is PLC program to Reset all Non-Retentive Outputs, along with program explanation and run time test cases.

List of Inputs and Outputs
 I:1/0	= Activate MCR			 (Input)
 I:1/1	= Activate Non-retentive output1 (Input)
 I:1/2	= Activate Non-retentive output2 (Input)
 I:1/3	= Activate retentive output	 (Input)
 O:2/1	= Non-retentive output1		 (Output)
 O:2/2	= Non-retentive output2		 (Output)
 O:2/3	= Retentive output		 (Output)

Ladder Diagram to reset all non-retentive outputs (Allen Bradley)plc-program-reset-non-retentive-outputs-01

Program Description
  • As the theory of MCR describes, it needs to be turned on to be inactive.
  • When I:1/0 is high, all the rungs perform operation normally which are in between RUNG000 to RUNG004. Others are independent of MCR.
  • When I:1/0 goes low, it forces all the NON-RETENTIVE outputs O:2/1 and O:2/2 to be de-energized.
  • However O:2/3 is not affected by MCR since it is –(L)– instruction.
Runtime Test Cases

MCR inactiveplc-program-reset-non-retentive-outputs-02
MCR activeplc-program-reset-non-retentive-outputs-03


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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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