Washing Machine Panel based on Embedded Systems using STM32NUCLEO-L476RG

02 · Project Introduction

This project involved the design and implementation of a simulated washing machine control panel using the STM32L476RG Nucleo-64 microcontroller development board.

The system provides two primary control modes:

• Fully Automatic Mode

• Manual Adjustment Mode

The control panel integrates buttons, LED indicators, a timer display, a pressure sensor, a water temperature sensor, a photoresistor, a thermistor, a potentiometer, and a buzzer. Users can control the power, select an operating mode, execute a washing cycle, monitor sensor parameters, and check the current operating status.

The system also communicates with a computer through a serial interface, allowing operating parameters, button inputs, and washing machine status information to be monitored in real time.

03 · Project Objectives

The project aimed to develop a complete washing machine control system with the following functions:

• Switch the washing machine on and off

• Select between different washing modes

• Indicate the currently selected mode

• Measure parameters such as water temperature and pressure

• Make operating decisions based on sensor readings

• Start and complete the selected washing cycle

• Notify the user when the cycle is complete

• Display the operating status through a serial interface

Beyond the basic requirements, the project introduced automatic and manual operation, safety checks, abnormal-condition alerts, and cycle pause functionality.

04 · Hardware Components

The washing machine control panel consists of the following components:

• STM32L476RG Nucleo-64 development board

• Power button

• Start button

• Confirmation button

• Return button

• LED status indicators

• Timer display

• Pressure sensor

• Water temperature sensor

• Photoresistor

• Thermistor

• Potentiometer

• Buzzer

• Serial communication interface

The buttons are used for power control, mode selection, program activation, confirmation, and return operations. The LEDs indicate the current operating stage, while the sensors collect temperature, pressure, and other environmental parameters.

The buzzer provides audible notifications when a washing cycle is complete or when the system detects an abnormal condition.

05 · System Functions

Power Control

The user can switch the simulated washing machine on or off using the power button.

When the system is powered on, it initializes the buttons, LEDs, sensors, buzzer, and serial interface before entering the mode-selection stage. When the power is switched off, the current operation is stopped and the status indicators are disabled.

Washing Mode Selection

The system supports two operating modes: fully automatic mode and manual adjustment mode.

The user can switch between these modes using the control buttons. LED indicators and serial messages are used to confirm the currently selected mode.

Parameter Monitoring

Before and during a washing cycle, the system reads data from the sensors and checks parameters such as water temperature and pressure.

The measured values are used to determine whether the system can operate safely. If an overload, excessive temperature, or another abnormal condition is detected, the washing process is paused and the buzzer alerts the user.

Cycle Execution

After confirming the operating mode and washing program, the user can press the start button to begin the cycle.

The system controls the simulated water inlet, washing, draining, and spinning stages according to the selected mode. LEDs indicate the current stage, and the buzzer notifies the user when the complete cycle has finished.

Serial Status Interface

The system communicates with a computer through a serial connection and displays the operating status using a serial monitor.

The interface can display:

• Current power status

• Selected operating mode

• Current washing stage

• Sensor readings

• Button inputs

• Program running time

• Abnormal conditions and warnings

• Cycle completion notifications

The serial interface supports both real-time monitoring and software debugging.

06 · Fully Automatic Mode

In fully automatic mode, the system completes the entire washing process according to a predefined sequence.

The primary workflow is:

1. Power on the washing machine

2. Initialize the control panel and sensors

3. Check pressure, temperature, and other input parameters

4. Select a washing cycle

5. Execute the water inlet stage

6. Execute the washing stage

7. Execute the draining stage

8. Execute the spinning stage

9. Complete the cycle and notify the user

The system automatically moves between the different stages without requiring the user to control each operation individually.

During operation, the sensors continuously participate in safety monitoring. If the system detects an overload or excessive temperature, the program pauses immediately and activates the buzzer. The user can also manually pause the washing cycle by pressing the relevant control button.

07 · Manual Adjustment Mode

Manual adjustment mode gives the user greater control over the washing process.

After the system has started and completed its sensor checks, the user can manually select a washing cycle or choose a specific operation to perform independently, including:

• Water inlet

• Washing

• Draining

• Spinning

This mode allows the user to adjust the washing process according to their requirements without completing the entire predefined automatic cycle.

Manual mode retains the same safety-monitoring, abnormal-condition alert, and pause functions as automatic mode. If an overload, high temperature, or another unsafe condition is detected, the current operation is paused and the user is notified.

08 · Software Design

The system software was primarily developed in C++ using Mbed Studio or Keil Studio.

The program applies several fundamental programming concepts:

• Loops

• Conditional statements

• Functions

• Input and output control

• State evaluation

• Mode switching

• Sensor data processing

• Serial output

To improve readability and maintainability, the system was divided into relatively independent functions for power control, mode selection, sensor monitoring, washing-cycle execution, exception handling, and serial communication.

Loops are used to continuously monitor button inputs and sensor states. Conditional statements determine the next system operation according to user inputs and measured parameters.

09 · Input and Output Control

The project integrates the digital input, digital output, and analog input capabilities of the microcontroller.

Input Components

The system reads data from:

• Control buttons

• Water temperature sensor

• Pressure sensor

• Photoresistor

• Thermistor

• Potentiometer

Output Components

The system controls:

• LED indicators

• Buzzer

• Timer display

• Serial status messages

• Simulated washing-process states

By combining input monitoring with output control, the system can respond to user operations and changing sensor conditions in real time.

10 · Safety and Exception Handling

Several safety-checking and protection mechanisms were added to improve the reliability of the simulated washing machine control system.

These mechanisms include:

• Checking sensor parameters before starting a cycle

• Continuously monitoring water temperature during operation

• Detecting whether pressure or load exceeds the safe range

• Automatically pausing the program under abnormal conditions

• Activating the buzzer to alert the user

• Displaying fault information through LEDs and the serial interface

• Allowing the user to pause and resume the program manually

These functions enable the system to make decisions based on external inputs instead of only following a fixed sequence.

11 · Development and Testing

The project was developed using an incremental implementation and integration approach.

Individual components-including the buttons, LEDs, sensors, buzzer, and serial interface-were tested separately. After each component was confirmed to operate correctly, it was integrated into the complete washing machine control program.

The development process included:

• Planning the system functions and operating workflow

• Building the hardware control panel

• Testing individual input and output components

• Developing basic control functions

• Implementing fully automatic mode

• Implementing manual adjustment mode

• Adding sensor checks and safety functions

• Implementing serial status output

• Integrating, testing, and optimizing the complete system

This incremental method made it easier to identify individual module problems before full system integration and provided stable versions of the program throughout development.

12 · Debugging and Optimization

A significant part of the development process involved troubleshooting and debugging.

The main issues included:

• Unstable button-input detection

• Logical conflicts between control conditions

• Incorrect transitions between washing stages

• Sensor values affecting program decisions

• Loops preventing the system from responding promptly

• Inconsistencies between LEDs, buzzer alerts, and serial messages

• State-transition problems between automatic and manual modes

To address these issues, I repeatedly inspected and restructured the code. Individual module testing, serial output observation, and conditional-logic adjustments were used to improve the stability of the complete system.

13 · Project Demonstration

The final presentation demonstrated the primary functions of the washing machine control panel, including:

• System power control

• Automatic and manual mode selection

• Washing-cycle selection

• Simulation of water inlet, washing, draining, and spinning

• Sensor data acquisition

• Abnormal-condition detection and buzzer alerts

• Manual cycle pausing

• LED status indication

• Serial status monitoring

• Cycle-completion notifications

The demonstration highlighted the interactions between the hardware components and showed how a user could operate the complete washing process through the control panel.

14 · Project Outcome

Through this project, I developed a stronger understanding of the relationship between input, processing, and output in an embedded system. I also improved my ability to develop microcontroller software using C++.

The project provided practical experience in:

• STM32 microcontroller development

• Digital input and output control

• Analog sensor data acquisition

• Button and LED control

• Buzzer notifications

• Serial communication

• C++ function design

• Loops and conditional statements

• Control-flow design

• Software debugging and code optimization

The development process demonstrated that embedded-system projects require more than controlling individual hardware modules. Multiple components must operate reliably according to a unified control logic.

Troubleshooting problems related to program logic, state transitions, and component interactions also strengthened my engineering problem-solving and debugging abilities.