Controlling of conveyors with interlock

PLC Program: Conveyor Sequence Control and Interlocking

Problem Description

A feeder drops material onto Conveyor 1, which then transfers the material to Conveyor 2 for further processing. The system must function automatically—conveyors should start based on material detection using load cells. The system must ensure sequence control and interlocking to avoid collisions.

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System Components and Setup

• PLC Type: Siemens S7-300

• Software: TIA Portal

• Material Detection: Load Cells (preferred over proximity or limit switches for higher reliability)

I/O List

Inputs

Address	Description
I0.0	START Push Button
I0.1	STOP Push Button
I0.2	Load Cell 1 (Conveyor 1)
I0.3	Load Cell 2 (Conveyor 2)

Outputs

Address	Description
Q0.0	Cycle ON Indicator
Q0.1	Conveyor 1 Motor
Q0.2	Conveyor 2 Motor
Q0.3	Feeder Motor

Ladder Logic Program Description

Network 1: System Start Logic

• When START (I0.0) is pressed and system is not in STOP mode (I0.1 not active), Cycle ON (Q0.0) is latched to keep the system running.

• This also starts the Feeder Motor (Q0.3) to begin dropping material.

Network 2: Conveyor 1 Activation

• If Cycle ON (Q0.0) is active and Load Cell 1 (I0.2) detects material, then Conveyor 1 Motor (Q0.1) turns ON.

Network 3: Conveyor 2 Activation

• When Load Cell 2 (I0.3) detects material (i.e., material has transferred from Conveyor 1 to Conveyor 2), then Conveyor 2 Motor (Q0.2) turns ON.

Network 4: Emergency Stop Logic

• If STOP Button (I0.1) is pressed, all outputs are turned OFF by resetting the Cycle ON (Q0.0) latch.

Functional Sequence (Interlocking Logic)

1. START Button Pressed (I0.0 = 1):

   • Q0.0 (Cycle ON) = 1

   • Q0.3 (Feeder Motor) = 1

2. Material Detected on Conveyor 1 (I0.2 = 1):

   • Q0.1 (Conveyor 1 Motor) = 1

3. Material Transferred to Conveyor 2 (I0.3 = 1):

   • Q0.2 (Conveyor 2 Motor) = 1

4. STOP Button Pressed (I0.1 = 1):

   • All outputs reset (Q0.0–Q0.3 = 0)

Runtime Test Cases

Inputs	Outputs	Physical Behavior
I0.0 = 1	Q0.0 = 1	Cycle ON Lamp turns ON
I0.2 = 1	Q0.1 = 1	Conveyor 1 Motor starts
I0.3 = 1	Q0.2 = 1	Conveyor 2 Motor starts
I0.1 = 1	All Q outputs = 0	System stops

Conclusion

This PLC program ensures automatic sequencing and interlocking of conveyor belts using load cell feedback. It minimizes manual intervention, improves reliability, and provides a robust material handling solution using Siemens S7-300 and TIA Portal.

Would you like me to also draw the ladder diagram or generate an image of the conveyor setup for better