Sequential Motor Control with Time delay using Schneider M340 PLC

Introduction

Sequential motor control with time delay is a widely used industrial automation technique where multiple motors are operated one after another in a fixed sequence, with a programmed delay between each operation. Instead of starting all motors simultaneously, which can cause excessive current surges and mechanical stress, this method ensures safe operation, load management, and smooth functioning of machines.

The system is typically implemented using a Programmable Logic Controller (PLC), which provides flexibility, reliability, and easy modification of timing or sequence. Timers within the PLC are used to introduce delays between the starting of each motor, ensuring controlled and predictable operation.

This technique is essential in industries where multiple motors are part of a process, such as conveyor systems, pumping stations, HVAC systems, and automated manufacturing plants.

     Diagram: -

 

 

Problem Statement

In industrial environments, starting multiple motors simultaneously can lead to:

High inrush current, causing voltage dips and possible equipment damage.

Mechanical stress on connected machinery.

Reduced safety due to uncontrolled startup.

To overcome these issues, a sequential motor control system with time delay is required. This system ensures motors start one after another, with defined delays, improving safety, efficiency, and equipment lifespan.

 

Components Used

Start Push Button (NO – Normally Open): Initiates the process.

Stop Push Button (NC – Normally Closed): Stops the system instantly.

Relay Coil: Provides latching after pressing the start button.

Motors (M1, M2, M3, M4, M5): Represent different stages of operation.

Timers (TON_1, TON_2, TON_3, TON_5): Provide time delays between motor operations.

 

Ladder Logic Concept

The PLC program is designed using ladder logic. The Start button energizes the relay coil, which latches the system. Timers are then activated sequentially, each controlling the delay before the next motor starts. The Stop button breaks the latch, shutting down all motors immediately.

 

Working Principle

Step 1: System Start

When the Start button is pressed, the relay coil energizes and latches itself using its own contact.

The system remains ON even after releasing the Start button.

Pressing the Stop button breaks the latch, stopping all motors instantly.

Step 2: First Motor (M1) Operation

After the relay is activated, Motor M1 starts immediately.

No delay is applied before M1, making it the starting point of the sequence.

 

Step 3: Second Motor (M2) with Delay

Timer TON_1 is activated with a preset delay of 30 seconds.

After this delay, its output turns ON Motor M2.

M2 starts 30 seconds after M1.

 

Step 4: Third Motor (M3) with Additional Delay

Timer TON_2 is used for Motor M3, with a delay of 40 seconds.

Once the timer completes, M3 is turned ON.

M3 starts after M2 with a defined delay.

 

Step 5: Fourth Motor (M4)

Timer TON_5 controls Motor M4 with a delay of 50 seconds.

After the timer finishes, M4 starts automatically.

This ensures proper sequencing and avoids overload.

 

Step 6: Fifth Motor (M5)

Finally, Timer TON_3 with a delay of 60 seconds is used to start Motor M5.

M5 is the last motor in the sequence and starts after all previous motors.

 

Interlocking Concept

Interlocking is a critical safety feature in ladder logic. Contacts of other motors (M2, M3, M4, M5) are used in series or parallel to ensure:

Motors start in the correct order.

A motor will not start unless previous conditions are satisfied.

Prevents unsafe operations and system faults.

 

Advantages of Sequential Motor Control

Reduced Starting Current: Motors do not start simultaneously, avoiding high inrush current.

Improved Safety: Controlled and predictable operation.

Energy Efficiency: Prevents power spikes and optimizes load distribution.

Extended Machine Life: Smooth startup reduces mechanical wear and tear.

Flexibility: Timing and sequence can be easily modified in PLC programming.

Applications

Conveyor Belt Systems: Motors start sequentially to move products smoothly.

Industrial Production Lines: Ensures machines operate in the correct order.

Pumping Systems: Controls multiple pumps with delays to manage water flow.

HVAC Systems: Sequential startup of fans and compressors prevents overload.

Automated Manufacturing Plants: Provides safe and efficient motor operation.

Conclusion

Sequential motor control with time delay is a fundamental automation technique in modern industries. By using PLC ladder logic and timers (TON), multiple motors can be controlled efficiently in a fixed sequence.

The system ensures:

Smooth operation

Enhanced safety

Efficient use of electrical power

Longer equipment lifespan

The project demonstrates how motors M1 to M5 are started one by one using different time delays (30s, 40s, 50s, 60s). This method is reliable, flexible, and widely applicable in industrial automation.

Learning Outcomes

Understanding of timers and sequencing in PLC programming.

Practical exposure to ladder logic design.

Application of interlocks and latching for safety.

Real‑world implementation of automation principles.

 

 

Automatic Fan and AC Control using Schneider M340 Programable Logic Conrtroller

In many places like classrooms, offices, and small halls, fans and air conditioners are often left ON even when there are no people inside. This leads to unnecessary power consumption and higher electricity bills. Also, manually switching devices ON/OFF every time someone enters or leaves is not efficient. So, there is a need for an automatic system that can control fan and AC based on the number of people present in the room.

Schematic:

The system consists of two IR sensors placed at the entry and exit door. These sensors are connected to a PLC. The PLC is also connected to output devices like a fan and an air conditioner through relays or contractors. A display unit can also be connected to show the number of visitors inside the room.

LADDER DIAGRAM:

Solution:

The solution is to design a PLC-based visitor counter system. When a person enters, the entry sensor detects and increments the count. When a person leaves, the exit sensor detects and decrements the count. If the count is greater than zero, the PLC will turn ON the fan. If the count increases beyond a certain number (for example, more than 3 people), the AC will also turn ON. When the count becomes zero, both fan and AC will turn OFF automatically.

 

PLC Program (Ladder Diagram Description):

-  Use two inputs: I0.0 for Entry Sensor and I0.1 for Exit Sensor

-  Use one counter for counting number of persons

-  Increment counter on I0.0 signal

-  Decrement counter on I0.1 signal

-  If counter value > 0, turn ON output Q0.0 (Fan)

-  If counter value > 3, turn ON output Q0.1 (AC)

-  If counter value = 0, turn OFF both outputs

 

Explanation:

In this system, PLC plays the main role in controlling the entire operation. The IR sensors detect movement and send signals to the PLC. Based on these signals, the PLC program updates the count value using up and down counting logic. This count is then used as a condition to control output.

 

When at least one person is inside the room, the fan is automatically turned ON to provide ventilation. When more people are present, the temperature may rise, so the AC is also turned ON for better comfort. When all people leave, the system automatically turns OFF all devices, saving energy.

 

This system is very useful in real-life applications like classrooms, meeting rooms, and offices. It reduces human effort, saves electricity, and increases efficiency. The project also helps in understanding PLC programming, sensors, and automation concepts in a practical way.

 

Sequential Light control using Schnieder M340 PLC

In many decorative and industrial applications, multiple lights are used to create visual effects or indicate process status. Controlling these lights manually is inefficient, inconsistent, and prone to human error. A PLC‑based sequential light control system automates this process, ensuring precise timing, repeatability, and flexibility.

This system turns ON lights one after another in a defined sequence, maintains them for a set duration, and then turns them OFF in the same or reverse order. Such automation is widely used in advertisement displays, event lighting, runway indicators, and process signalling systems.

Schematic:

The system consists of:

- PLC

- 6 Output

- Start Push Button (Input)

- Stop Push Button (Input)

- Timer blocks inside PLC

Solution

A PLC-based sequential light system is designed using ladder logic. When the Start button is pressed, the lights turn ON one by one with a time delay between each light. After all lights are ON, they either turn OFF sequentially or the cycle repeats. The Stop button stops the process anytime.

 

PLC Program (Ladder Logic):

 

Explanation:

Initially, when the Start push button is pressed, the system is latched using an internal memory bit (M0). This latch ensures continuous operation until the Stop button is pressed. Once latched, the first timer (T1) is activated.

After a delay of 5 seconds, Timer T1 completes its cycle and turns ON Light 1 (L1). The activation of L1 triggers the next timer (T2), which after another 5‑second delay turns ON Light 2 (L2). This sequential process continues — L2 activates T3, L3 activates T4, and so on — resulting in a smooth, timed lighting sequence.

The Stop push button is used to break the latch (reset M0), immediately halting the entire process and turning all lights OFF.

System Highlights

Sequential Operation: Lights turn ON one after another with precise timing.

Programmable Delay: Timing between lights can be easily modified in the PLC program.

Safe Control: The latch ensures controlled operation and immediate stop when required.

Flexible Design: Sequence can be reversed or looped continuously.

Applications

Decorative lighting systems for events and exhibitions

Advertisement and display boards

Runway or pathway lighting

Industrial indication and signalling systems

Advantages

Flexibility: Timing and sequence can be adjusted without hardware changes.

Reliability: PLC ensures consistent and error‑free operation.

Ease of Modification: Logic can be updated quickly for different patterns.

Educational Value: Demonstrates timers, sequencing, and ladder logic fundamentals in PLC programming.

 

Conveyor Sorting System Schneider M340 PLC

In modern industrial manufacturing, automatic sorting of products is a critical requirement. A Conveyor Sorting System is used to separate different types of products on a conveyor belt and direct them to their respective output lanes without any manual effort. This system uses proximity sensors, pneumatic pushers (sorters), a conveyor motor, and a Programmable Logic Controller (PLC) to identify and sort products automatically. In this assignment, the Conveyor Sorting System is designed to sort three types of products: Plastic Bottles, Aluminium Cans, and Steel Cans. The animation was designed to simulate real-life operation using counter values for product position tracking.

SYSTEM OVERVIEW: -

The Conveyor Sorting System consists of one main conveyor belt and three separate output lanes, one for each product type. The three products handled by the system are:

1. Plastic Bottle

2. Aluminium Can

3. Steel Can

Each product has its own dedicated pneumatic sorter (salter), sensors, counters, and indicator in the PLC program. The operator selects the product type by pressing the corresponding button on the control panel. Once selected, the product appears on the conveyor and moves toward its designated sorting lane.

COMPONENTS USED: -

Programmable Logic Controller (PLC)

Control Panel / Operator Interface

Conveyor Belt Motor

Pneumatic Sorter / Salter (3 units - one per product)

Proximity Sensors (Sensor0 and Sensor1 for each product)

CTU (Count Up) and CTUD (Count Up-Down) Counters

TON Timer

Push Buttons: MAIN_START and MAIN_STOP

Product Selection Buttons: Plastic_Bottle, Aluminium_Can, Steel_Can

WORKING: -

When the MAIN_START button is pressed, the system becomes active and the main indication light turns ON. The operator then selects the product type by pressing one of the three product buttons on the control panel.

Once a product is selected, the corresponding product animation appears on the conveyor belt. The PLC uses CTU counter values to track the horizontal and vertical position of the product on the conveyor. As the counter value increases, the product moves forward on the belt toward its assigned sorting station.

When the product reaches the sorting position, the virtual Sensor0 detects the product, and the salter (pneumatic pusher) begins to move downward. Sensor1 confirms the product position, and the salter pushes the product off the main conveyor into the correct output lane box. The CTUD counter values control the up and down movement of the salter.

After sorting, the product counter for that lane increases by one, the salter retracts upward, and the system resets for the next product cycle. The MAIN_STOP button can be pressed at any time to stop all operations immediately.

HMI SCREEN VIEWS: -

Fig. 1: Conveyor Sorting System - Initial State

 

Fig. 2: Conveyor Sorting System - Sorter Activated

 

Fig. 3: Conveyor Sorting System - Product Sorted

 

PLC LOGIC DESCRIPTION: -

The PLC logic for this system is divided into separate sections for each product. The key logic elements used are:

CTU (Count Up) Counters: Used to count the horizontal (Ho) and vertical (Vo) movement of the product on the conveyor. When the horizontal counter value reaches the preset value, the product is considered to have reached the sorting station.

CTUD (Count Up-Down) Counter: Used to control the salter position. The salter counts up to move down and counts down to retract upward. This simulates the pneumatic cylinder extend and retract operation.

TON Timer: A 0.5 second ON-delay timer (TON_1) is used to control the speed of the conveyor animation and product movement cycle.

Virtual Sensors (Sensor0 and Sensor1): These are not physical sensors but are simulated using comparison instructions (EQ and GE) applied to counter values. Sensor0 triggers when the horizontal count equals 6, and Sensor1 triggers when the vertical count equals 3, to replicate sensor detection logic.

Product Counter (CTU): After the sorting is complete, a separate counter records the total number of products sorted into each output lane.

PLC LOGIC:-

CONCLUSION: -

The Conveyor Sorting System demonstrates the practical application of PLC programming in industrial automation. The use of counter values to simulate product movement and sensor detection is an innovative approach that allows realistic operation without physical hardware. The system successfully sorts three different product types, Plastic Bottles, Aluminium Cans, and Steel Cans, into separate output lanes using pneumatic sorters controlled by PLC logic. This project helped in understanding the use of CTU, CTUD counters, TON timers, and comparison instructions in real-life automation scenarios.

 By Vicky