How to Program Timers into a Washing Machine Using Siemens PLC

Key Takeaways

What is the importance of timers in washing machine automation?Timers control various stages of the washing cycle, ensuring precise operation and efficiency.
Which Siemens PLC models are commonly used?S7-1200, S7-1500.
What types of timers are used in Siemens PLC programming?ON-Delay (TON), OFF-Delay (TOF), Pulse Timer (TP), Retentive On-Delay (TONR).
What software is required for programming?Siemens TIA Portal.
What is a practical example of using timers in a washing machine?Using ON-Delay for the start, Pulse Timer for drum control, and OFF-Delay for rinse cycles.


ControlNexus, established in 2013, is a leading provider of Siemens PLCs, HMIs, and Inverters. At ControlNexus, we understand the vital role that programmable logic controllers (PLCs) play in industrial automation. Specifically, Siemens PLCs are renowned for their reliability and efficiency in automating complex processes like washing machine cycles. In this article, we will delve into how to program timers into a washing machine using Siemens PLCs.

Understanding Timers in Siemens PLC

Types of Timers

Timers are essential components in PLC programming, providing control over the timing of operations. In Siemens PLCs, there are four main types of timers:

  • ON-Delay Timer (TON): Activates after a set delay once the input is triggered.
  • OFF-Delay Timer (TOF): Deactivates after a set delay once the input is turned off.
  • Pulse Timer (TP): Outputs a pulse of a specified duration when triggered.
  • Retentive On-Delay Timer (TONR): Accumulates time across multiple inputs and retains the timing even after the input is deactivated.

Practical Applications

Timers are used to control the sequence and duration of various stages in a washing machine cycle. For example:

  • ON-Delay Timer: Used to start the washing cycle after ensuring the door is closed.
  • OFF-Delay Timer: Used to control the rinse cycle duration.
  • Pulse Timer: Used to control the pulsing action of the drum during the wash cycle.

Preparing for Programming

Necessary Hardware and Software

To get started with programming a Siemens PLC for a washing machine, you’ll need the following:

  • Siemens PLC: Recommended models include the S7-1200 and S7-1500.
  • Siemens TIA Portal: This software is essential for programming and configuring your PLC.

Basic Setup and Configuration

  1. Creating a New Project: Open TIA Portal and create a new project.
  2. Configuring the Hardware: Add your PLC model to the project and configure its hardware settings.

Step-by-Step Guide to Programming Timers

Step 1: Setting Up the Project in TIA Portal

  • Create a New Project: Launch TIA Portal, select ‘Create a new project,’ and enter the project details.
  • Configure Hardware: Add the S7-1200 or S7-1500 PLC to your project. Configure the necessary modules and assign IP addresses.

Step 2: Adding and Configuring Timers

  • ON-Delay Timer (TON): Drag and drop the TON instruction into your network. Set the delay time and assign input and output variables.
  • OFF-Delay Timer (TOF): Similarly, add the TOF instruction, configure the delay duration, and assign the necessary variables.
  • Pulse Timer (TP): Insert the TP instruction and configure it to generate a pulse for the specified duration.
  • Retentive On-Delay Timer (TONR): Add the TONR instruction to accumulate time across multiple inputs, ensuring the timing is retained even after deactivation.

Step 3: Creating the Ladder Logic for Timers

  • ON-Delay Timer Logic: Create a network with the TON instruction. This timer will activate the washing cycle after a set delay, ensuring all safety checks are completed.
  • OFF-Delay Timer Logic: Implement the TOF instruction to control the duration of the rinse cycle, ensuring it runs for the specified time after activation.
  • Pulse Timer Logic: Use the TP instruction to control the pulsing action of the drum, ensuring efficient washing with intermittent drum movements.
  • Retentive On-Delay Timer Logic: Add the TONR instruction to manage cumulative operations, such as prolonged heating cycles, that require accumulated timing.

Practical Example: Programming a Washing Machine Cycle

Step 1: Input and Output Configuration

  • Inputs: Define inputs such as the start button (I0.0) and door sensor (I0.1).
  • Outputs: Define outputs like the water valve (Q0.0) and drum motor (Q0.1).

Step 2: Programming the Wash Cycle

  • Initiating the Wash Cycle: Use an ON-Delay Timer to start the wash cycle after verifying that the door is securely closed.
  • Controlling the Drum Motor: Implement a Pulse Timer to control the intermittent movement of the drum, ensuring thorough washing.
  • Rinse Cycle: Use an OFF-Delay Timer to manage the rinse cycle, allowing it to run for the required duration.

Step 3: Incorporating Safety Features

  • Interlocks and Safety Checks: Use interlocks to ensure that the machine does not operate unless all safety conditions are met, such as the door being closed and locked.
  • Error Handling: Program the PLC to detect and respond to errors, such as an open door, by pausing the cycle and alerting the user.

Best Practices and Tips for Effective PLC Programming

Thorough Testing and Simulation

Testing and simulation are critical in PLC programming. By using the Siemens TIA Portal’s simulation tools, you can verify the correctness of your ladder logic before deploying it to the actual hardware. This process helps to identify and fix any issues early, ensuring a smoother operation when the PLC is implemented in the washing machine.

Keeping the Code Organized and Well-Documented

Maintaining organized and well-documented code is essential for future troubleshooting and updates. Use clear and descriptive names for variables and functions. Add comments to explain the purpose of each part of the program. This practice not only helps you but also assists others who might work on the project in the future.

Ensuring Flexibility and Scalability

Design your PLC program with flexibility and scalability in mind. This means creating a modular code that can be easily modified or expanded to accommodate additional features or changes in the washing machine’s functionality. For example, if a new washing cycle needs to be added, the program should allow for this addition without extensive rework.


Programming timers into a washing machine using Siemens PLCs is a sophisticated task that, when done correctly, enhances the efficiency and reliability of the machine. By understanding the different types of timers, setting up your project correctly in TIA Portal, and following best practices for PLC programming, you can create an effective and robust washing machine automation system.

At ControlNexus, we offer a wide range of Siemens PLCsHMIs, and Inverters to support your automation needs. Established in 2013, our expertise and comprehensive product line ensure that you have the tools and support needed for your projects. For more detailed guidance and additional resources, visit our website and explore our comprehensive guides and tutorials.

Additional Resources

By following this guide and utilizing the resources available at ControlNexus, you can confidently program timers into a washing machine using Siemens PLCs, achieving optimal automation and performance.


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