PLC Conveyor Sorting System using OpenPLC

Project Overview

This project implements an automated conveyor sorting system using OpenPLC Editor v4 and Ladder Logic (IEC 61131-3).

The system controls a conveyor belt, detects incoming boxes, identifies tall boxes using a height sensor, and automatically activates a reject mechanism after a configurable delay using a TON timer. The design also incorporates industrial safety features such as Start/Stop controls and an Emergency Stop circuit.

This project demonstrates the implementation of industrial PLC programming concepts commonly used in automated manufacturing and material handling systems.

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Features

• Start/Stop push-button control
• Emergency Stop (E-Stop) safety circuit
• Conveyor motor control
• Box detection using a sensor
• Height-based box classification
• Automatic reject mechanism
• TON (On-Delay) timer implementation
• Warning lamp indication during reject cycle
• Modular ladder logic implementation

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Software Used

• OpenPLC Editor v4
• OpenPLC Runtime v4
• Ladder Diagram (LD)
• Windows

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System Workflow

Start Button
      │
      ▼
System Starts
      │
      ▼
Conveyor Motor Runs
      │
      ▼
Box Detected
      │
      ▼
Height Sensor Checks Box
      │
      ├──────────────┐
      │              │
Normal Box      Tall Box
      │              │
      │              ▼
      │        Reject Cycle
      │              │
      │        TON Timer (2 s)
      │              │
      │              ▼
      │       Reject Pusher ON
      │              │
      │              ▼
      │       Warning Lamp ON
      │
      ▼
Continue Conveyor

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Inputs

Variable	Type	Description
StartPB	BOOL	Start push button
StopPB	BOOL	Stop push button
EStop	BOOL	Emergency stop
BoxSensor	BOOL	Detects arriving box
HeightSensor	BOOL	Detects tall boxes

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Outputs

Variable	Type	Description
ConveyorMotor	BOOL	Drives conveyor belt
RejectPusher	BOOL	Reject actuator
WarningLamp	BOOL	Indicates reject operation

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Internal Variables

Variable	Description
SystemRun	System latch
BoxDetected	Box detected flag
TallBox	Tall box identification
RejectCycle	Reject sequence trigger
TON0	TON timer instance
TimerPreset	Timer preset (2 seconds)

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Ladder Logic Networks

Network 1 — Start/Stop Latching

Implements the system start and stop logic with a seal-in (holding) circuit.

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Network 2 — Conveyor Motor

Runs the conveyor whenever the system is active and the Emergency Stop is not pressed.

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Network 3 — Box Detection

Detects the arrival of a box while the conveyor is operating.

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Network 4 — Tall Box Detection

Uses the height sensor together with the box detection signal to identify tall boxes.

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Network 5 — Reject Cycle

Initiates the reject sequence whenever a tall box is detected.

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Network 6 — Reject Pusher

Uses a TON timer to activate the reject pusher after a 2-second delay.

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Network 7 — Warning Lamp

Turns on a warning lamp whenever the reject cycle is active.

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Test Cases

Test Case	Expected Result	Status
Start Button	System starts	✅ Pass
Stop Button	System stops	✅ Pass
Emergency Stop	Conveyor stops immediately	✅ Pass
Conveyor Operation	Motor runs correctly	✅ Pass
Box Detection	Box detected successfully	✅ Pass
Tall Box Detection	Tall box identified	✅ Pass
Reject Cycle	Reject sequence initiated	✅ Pass
TON Timer	2-second delay before rejection	✅ Pass
Reject Pusher	Activates correctly	✅ Pass
Warning Lamp	Turns ON during reject cycle	✅ Pass

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Project Screenshots

Variable Declaration

See:

Media/Variables.png

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Networks 1 & 2

Media/network_1_2.png

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Networks 3, 4 & 5

Media/network_3_4_5.png

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Networks 6 & 7

Media/network_6_7.png

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Demonstration Video

A complete project demonstration is included in:

Media/PLC_ConveyorSorting_mp4.mp4

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Learning Outcomes

This project demonstrates practical experience with:

• PLC Programming
• Ladder Logic Design
• Industrial Automation
• IEC 61131-3 Standard
• TON Timers
• Safety Interlocks
• Conveyor Automation
• Sensor-Based Control Systems
• Sequential Logic Design

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Repository Structure

PLC-Conveyor-Sorting-System-OpenPLC
│
├── build/
├── devices/
├── pous/
├── Media/
│   ├── Variables.png
│   ├── network_1_2.png
│   ├── network_3_4_5.png
│   ├── network_6_7.png
│   └── PLC_ConveyorSorting_mp4.mp4
│
├── project.json
└── README.md

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Author

Aliya Rasheed

Mechatronics Engineering Student

NUST College of Electrical & Mechanical Engineering (CEME)

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License

This project is intended for educational and portfolio purposes.