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📦 Automatic Conveyor Box Sorting System

A PLC ladder logic simulation of an automatic box sorting system built using CodeSys. The system runs a conveyor to detect boxes, uses a pneumatic cylinder to push detected boxes off the line, counts processed boxes, and includes full Emergency Stop fault handling.

📌 Project Overview

Field Details
Platform CodeSys (Simulation)
Language Ladder Diagram (LD)
Function Detects boxes on conveyor and sorts them using a pneumatic cylinder
Counting Tracks sorted boxes using CTU counter
Safety Emergency Stop with Fault Lamp and latched fault handling

🔌 I/O Table

Inputs

Variable Type Description
START BOOL Start button — initiates the conveyor
STOP BOOL Stop button — halts the system
E_STOP BOOL Emergency stop — triggers fault condition
BOX_SENSOR BOOL Detects a box on the conveyor
F_LIMIT BOOL Forward limit switch — stops cylinder extension
B_LIMIT BOOL Backward limit switch — stops cylinder retraction
RESET_FAULT BOOL Resets the fault lamp after E_STOP condition
RESET_CTR BOOL Resets the box counter

Outputs

Variable Type Description
CONVEYOR BOOL Conveyor motor
FAULT_LAMP BOOL Indicates fault condition (set by E_STOP)
Cylinder_Extend BOOL Extends the pneumatic cylinder to push the box
Cylinder_Retract BOOL Retracts the cylinder back to home position
STOP_REQUEST BOOL Internal flag — requests conveyor stop when box detected
COUNT_REQUEST BOOL Internal flag — triggers box counter

Timers & Counters

Block Type Setting Description
CTU_0 CTU PRESENT_VALUE := 10 Counts sorted boxes, preset to 10
CURRENT_VALUE WORD — Current box count
R_TRIG_0 R_TRIG — Rising edge trigger — fires once when cylinder reaches back limit

🔄 System Sequence

  1. START pressed → CONVEYOR turns ON
  2. BOX_SENSOR detects a box → STOP_REQUEST set → conveyor stops, cylinder begins extending
  3. Cylinder extends until F_LIMIT is reached → Cylinder_Extend resets, Cylinder_Retract sets
  4. Cylinder retracts until B_LIMIT is reached → Cylinder_Retract resets
  5. On reaching B_LIMIT, rising edge trigger fires → COUNT_REQUEST set
  6. CTU_0 increments the box count
  7. Cycle repeats for the next box

Emergency Stop Sequence

  1. E_STOP pressed → FAULT_LAMP set
  2. Cylinder_Extend and Cylinder_Retract both reset — cylinder halts immediately
  3. Conveyor stops (FAULT_LAMP blocks conveyor rung)
  4. RESET_FAULT pressed → FAULT_LAMP resets → system ready to restart

🧩 Ladder Logic — Rung Breakdown

Rung Description
1 START with seal-in (CONVEYOR + COUNT_REQUEST) energizes CONVEYOR. STOP_REQUEST, STOP, E_STOP and FAULT_LAMP all break the circuit
2 E_STOP sets FAULT_LAMP and resets both Cylinder_Extend and Cylinder_Retract — immediate safe stop
3 BOX_SENSOR sets STOP_REQUEST and sets Cylinder_Extend — begins push sequence
4 F_LIMIT resets Cylinder_Extend and sets Cylinder_Retract — cylinder reverses direction
5 B_LIMIT resets Cylinder_Retract. Rising edge on B_LIMIT triggers COUNT_REQUEST
6 COUNT_REQUEST increments CTU_0. RESET_CTR clears the counter
7 RESET_FAULT resets FAULT_LAMP, clearing the fault condition

🖥️ Visualization

A simple HMI was built in CodeSys with manual test buttons for START, STOP, E_STOP, FAULT RESET, CTR RESET, and simulated sensor inputs (F_LIMIT, B_SENSOR, B_LIMIT) along with three status indicator lamps.

📁 Repository Structure

conveyor-box-sorting-plc/
├── media/
│   ├── ladder_logic.pdf
│   └── visualization_screenshot.png
├── README.md

🛠️ Tools Used

  • CodeSys 3.5 — PLC programming and simulation
  • Ladder Diagram (LD) — Programming language
  • Soft PLC simulation — No physical hardware required

👤 Author

S Navaneeth Krishna B.Tech — Electrical and Electronics Engineering Muthoot Institute of Science & Technology, Kerala

GitHub

📜 License

This project is open source and available for educational use.

About

PLC simulation of an automatic conveyor box sorting system with pneumatic cylinder control built in CodeSys

Topics

codesysconveyorindustrial-automationladder-logicplcsequential-control

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