Simple_Elevator

This repository contains a simple elevator control project developed in CODESYS.
The system controls one elevator serving four floors (L0–L3) and demonstrates basic PLC control logic using Ladder Diagram (LD) and Structured Text (ST).

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System Description

• L0 – L3
  Floor request buttons, either pressed inside the cabin or from each floor.
• at_L[ ]
  Boolean array indicating the current floor position of the elevator.
• go_L[ ]
  Boolean array storing the target floor requests.
• A go_L coil is activated only when:
  • the corresponding floor button is pressed
  • the elevator is not moving
• Floor requests remain active until:
  • the elevator reaches the selected target floor

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Control Logic

• At the beginning of each PLC cycle: all movement commands are reset
• The controller:
  • detects the current floor using the at_L[ ] array
  • determines the target floor from the active go_L[ ] request
• Elevator movement is decided inside a POU action block:
  • Current floor < Target floor → elevator moves up
  • Current floor > Target floor → elevator moves down
  • Current floor = Target floor → elevator stops
• If no valid floor position is detected:
  • the elevator enters a safe stop state

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Implementation

• Ladder Diagram (LD) : Handles floor request detection and latching

• Structured Text (ST) : Implements the decision logic for:

  • current floor
  • target floor
  • movement direction (up / down / stop)

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• Programming languages:
  • Ladder Diagram (LD)
  • Structured Text (ST)