Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Troubleshoot Allen Bradley PLC Logic
Share
Notification Show More
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > PLC Tutorials > Troubleshoot Allen Bradley PLC Logic

Troubleshoot Allen Bradley PLC Logic

Last updated: March 4, 2021 3:51 pm
Editorial Staff
PLC Tutorials Practical Questions
No Comments
Share
3 Min Read
SHARE

A engineer needs to write a program for an Allen-Bradley CompactLogix PLC to control a pressure relieving solenoid valve in a gas processing system.

Contents
Allen Bradley PLC LogicAnswer :

A pair of high-pressure control switches signals the PLC when to open the solenoid valve: one telling the PLC to open the valve after a 3-second time delay and the other (called the “high-high” switch, with a higher trip setting) telling the PLC to open the valve immediately.

A pushbutton switch serves as a manual override to open the solenoid valve immediately when pressed.

In all cases, the solenoid vent valve will remain open (energized) until pressure falls below the setting of a low-pressure gas switch.

The operating statuses of these switches are listed here:
  • Override pushbutton (normally-open): open when unpressed, closed when pressed
  • Low gas pressure (normally-closed): closed when pressure is less than 10 PSI, open when pressure exceeds 10 PSI
  • High gas pressure (normally-closed): closed when pressure is less than 30 PSI, open when pressure exceeds 30 PSI
  • High-high gas pressure (normally-open): open when pressure is less than 40 PSI, closed when pressure exceeds 40 PSI

Allen Bradley PLC Logic

The engineer’s first attempt is shown here, but it contains a serious error. Identify and correct this error:
Troubleshoot Allen Bradley PLC Logic

Answer :

The High pressure contact instruction should be drawn as normally-closed rather than normally-open as shown in the engineer’s first draft of the PLC program.

This particular switch signals a high-pressure condition by opening its contacts, since the real-world switch is normally-closed (NC).

We want the 3-second timer to begin timing when this switch senses a high pressure, and so we need the contact instruction to color when the real-world high-pressure switch trips (opens).

A PLC contact instruction that colors when it senses a “0” bit condition is a normally-closed (NC) instruction.

Share Your Answers

If you liked this article, then please subscribe to our YouTube Channel for PLC and SCADA video tutorials.

You can also follow us on Facebook and Twitter to receive daily updates.

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

PLC Example with Switches
Count the Number of Cartons in a Storage Area PLC Logic
How to Create New Project in Studio 5000?
PLC Program for Fish Feeding System
How to Operate a Group of Induction Motors using PLC Logic?
Resistance Temperature Detector (RTD) Questions – 1
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
Leave a Comment

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

What is PID Controller?
Smart Spray System using Wecon PLC
UPS Selection Factors for a Control System
How to Add Unspecified CPU in Tia Portal?
VFD Pros and Cons – Variable Frequency Drives
CX-Programmer Tutorial: 1 Button To Activate 4 Different Machines
How to use FIFO Block in TIA Portal? – Siemens PLC Programming
PLC Logic for Analog Alarms using Functional Block Diagram

Keep Learning

Basics of Sinking and Sourcing

Basics of Sinking and Sourcing – Automation System MCQ

PLC Code to Start & Stop Motor and Pump as per Logic

PLC Code to Start & Stop Motor and Pump as per Logic

4 TO 20 MA ANALOG CURRENT SIGNALS

Basics of 4 to 20 mA analog Signals

Practical Control Systems Questions & Answers

Practical Process Control System Questions & Answers – 3

Comparator used in Siemens S7-1200 PLC.

Siemens PLC Comparator Logic

Types of Instructions in PLC Programming

Types of Instructions in PLC Programming

PLC Program

PLC Program to Heat and Bend Glass Tubes

Start the Counting from a Preset Value in PLC

Start the Counting from a Preset Value in PLC

Learn More

Troubleshooting Ultrasonic Flow Meter Common Problems

Troubleshooting Ultrasonic Flow Meter Common Problems

Contact-Type-GWR-Level-Transmitter-Working-Animation

Probe Type GWR Level Transmitter Working Animation

What is an Actuator - Different Types of Actuators

What is an Actuator? – Different Types of Actuators

Transmission Lines Protection Questions Answers

Transmission Lines Protection Questions Answers

Timer-based vacuum cleaner in Schneider PLC

Schneider Electric PLC Timer Problem: Vacuum Cleaner

PlantPAx Select Add components into Project

How to Import PlantPAx Library?

Bottle’s Capping with Rotating Mechanism

PLC FBD Program for Bottle’s Capping with Rotating Mechanism

PLC based 4 Way Traffic Light Control System

PLC based 4 Way Traffic Light Control System

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?