Entrance–Exit Door and Elevator Control System

PLC ladder programming provides:

• Automation Efficiency – Doors open/close automatically when a person approaches.

• Safety Control – Emergency stop and interlocks prevent accidents.

• Flexibility – Manual override for security guards or authorized staff.

• Scalability – Easy to extend for more floors or doors.

This application is common in offices, malls, hospitals, and industrial facilities.

PLC Inputs and Outputs

Inputs (I)

• I0.0 → Entrance Sensor

• I0.1 → Exit Sensor

• I0.2 → Emergency Stop (NC)

• I0.3 → Manual Override Switch

• I1.0 – I1.2 → Elevator Call Buttons (Floors 1–3)

• I1.3 – I1.5 → Elevator Floor Position Sensors

• I1.6 → Elevator Door Closed Sensor

Outputs (Q)

• Q0.0 → Entrance Door Motor

• Q0.1 → Exit Door Motor

• Q1.0 → Elevator Up Motor

• Q1.1 → Elevator Down Motor

• Q1.2 → Elevator Door Motor

• Q1.3 – Q1.5 → Floor Indicator Lamps

Internal Memory (M)

• M0.0 → Elevator Moving Status

• M0.1 – M0.3 → Floor Requests

Timers (T)

• T0 → Entrance Door Timer (5 sec)

• T1 → Exit Door Timer (5 sec)

• T2 → Elevator Door Timer (7 sec)

Ladder Logic Program Rung Analysis

1. Entrance and Exit Door Control

• Automatic Opening: When a person is detected (I0.0 or I0.1), the respective door motor (Q0.0 or Q0.1) runs.

• Timer Function: Doors stay open for 5 seconds using timers (T0, T1).

• Manual Override: Security guard can force open the entrance door via I0.3.

• Safety Interlock: Doors will not open if the elevator is moving (M0.0).

2. Elevator Control Logic

• Call Buttons: Requests stored in memory bits (M0.1 – M0.3).

• Movement: Elevator moves up or down (Q1.0, Q1.1) until it reaches the requested floor.

• Door Logic: When at the correct floor, the door opens (Q1.2) for 7 seconds (T2).

• Priority: Floor 1 → Floor 2 → Floor 3 (based on rung evaluation).

3. Safety Features

• Emergency Stop (I0.2):

  • Immediately closes entrance/exit doors.

  • Stops elevator at its current floor.

  • Keeps elevator door open for passenger safety.

• Interlocks:

  • Elevator won’t move unless the door is closed (I1.6).

  • Entrance/Exit doors won’t open while the elevator is moving (M0.0).

System Operation Sequence

1. Person Approaches: Door sensor detects presence → Door opens → Timer runs → Door closes.

2. Call Elevator: Passenger presses a call button → Elevator moves to requested floor.

3. Elevator Arrival: Door opens for 7 seconds → Door closes automatically.

4. Emergency Stop: All movements stop instantly, elevator remains safe.