This week I worked on networking and communications, developing a Bluetooth-controlled networking scent diffuser system. The device uses ultrasonic sound generated by a piezo disk vibrating at 108kHz to convert water into water vapor. By soaking the water with essential oils, we are able to customize and create a scent display that can be controlled wirelessly via Bluetooth. This assignment demonstrates how Bluetooth networking can be implemented to enable remote control of devices, allowing multiple scent diffusers to be coordinated and controlled from a central interface. The networking capabilities transform the scent diffuser from a standalone device into a networked system that can be controlled remotely and integrated with other devices.

The scent diffuser system consists of several key components working together: Ultrasonic Piezo Disk: The core of the scent diffusion mechanism is an ultrasonic piezo disk that vibrates at 108kHz. This high-frequency vibration creates ultrasonic waves in the water, causing it to break apart into fine water vapor particles. The piezo disk is driven by an electronic circuit that generates the precise 108kHz frequency needed for efficient vaporization. Water and Essential Oil Mixture: The water reservoir contains water that has been soaked with essential oils. When the ultrasonic vibration converts the water into vapor, the essential oil molecules are carried along with the water vapor, creating a scented mist. Different essential oils can be used to create different scent profiles, allowing for customizable scent displays. Bluetooth Control: The system is controlled wirelessly via Bluetooth, allowing remote operation from smartphones, tablets, or computers. Bluetooth provides a convenient way to control the diffuser without physical contact, enabling features like scheduled operation, intensity control, and scent selection. Modular System Design: The system is designed with a modular architecture, allowing multiple diffusers to be set up and controlled independently or as a coordinated network. This modularity enables creating distributed scent displays where different scents can be active in different locations simultaneously.

Bluetooth was chosen as the communication protocol for this project because it provides wireless connectivity without requiring a network infrastructure, making it ideal for standalone scent diffuser units. The Bluetooth implementation enables: Remote Control: Users can control the scent diffuser from their smartphones or other Bluetooth-enabled devices, adjusting settings like intensity, duration, and scent selection without needing to physically interact with the device. Multiple Device Control: The Bluetooth networking allows a single control interface to connect to and manage multiple scent diffusers simultaneously. This enables coordinated control of a network of diffusers, each potentially diffusing different scents. Real-Time Communication: Bluetooth provides low-latency communication, allowing for responsive control and real-time status updates from the diffuser units. This ensures that commands are executed promptly and users receive immediate feedback. Low Power Consumption: Bluetooth Low Energy (BLE) can be used to minimize power consumption, making the system suitable for battery-powered or energy-efficient operation. The Bluetooth implementation required configuring the microcontroller to act as a Bluetooth peripheral, defining communication protocols for commands and status updates, and developing a control interface that can connect to and manage multiple devices.

The ultrasonic vaporization system uses a piezo disk to generate high-frequency vibrations at 108kHz. This frequency is specifically chosen because it efficiently creates cavitation in water, producing fine mist particles without heating the water. The process works as follows: 1. Piezo Disk Activation: An electronic driver circuit applies an alternating voltage to the piezo disk at 108kHz, causing it to vibrate at this ultrasonic frequency 2. Cavitation: The ultrasonic vibrations create microscopic bubbles in the water through cavitation, where rapid pressure changes cause water molecules to separate 3. Mist Generation: The cavitation bubbles collapse, releasing energy that breaks the water surface tension and creates fine water vapor particles 4. Scent Dispersion: The essential oils dissolved in the water are carried along with the water vapor, creating a scented mist that diffuses into the air The 108kHz frequency is optimal for this application because it provides efficient vaporization while remaining within safe ultrasonic ranges. The piezo disk must be precisely driven at this frequency to achieve consistent mist production.

Based on feedback from Quentin, the simplest ultrasonic scent diffuser can be built using the following core components and principles: Microcontroller: Used to generate the necessary high-frequency signal. The microcontroller's timers and PWM (Pulse Width Modulation) features are capable of producing the required 108kHz frequency, as confirmed by datasheet specifications. Power Switching Component - MOSFET: A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is used as a switch to control the high-current/high-voltage supply for the mist maker. • Connection: The microcontroller output (GPIO pin) connects to the Gate of the MOSFET • Function: The MOSFET switches the high-current/high-voltage supply for the mist maker, driven by the low-current signal from the microcontroller. This allows the low-power microcontroller to control the higher-power ultrasonic atomizer safely and efficiently Atomizer Component: A simple mist maker module is used, specifically the DC 5V Mist Maker Atomizing Module Kit DIY USB Humidifying Driving Circuit Board. This kit is chosen for its ease of use and integrated driver circuitry, simplifying the build significantly compared to sourcing individual components. The integrated driver circuit handles the complex signal generation needed for the ultrasonic atomization. Target Frequency: The required ultrasonic operating frequency for atomization is 108 kHz. This frequency is totally doable using standard microcontroller timers and PWM features, making it feasible to implement with common microcontroller platforms. This component selection and design approach provides a straightforward path to building a functional ultrasonic scent diffuser, balancing simplicity with effectiveness.

The scent diffuser system uses a modular architecture that allows multiple units to be deployed and controlled independently or as a coordinated network: Individual Unit Control: Each scent diffuser operates as an independent Bluetooth peripheral, allowing it to be controlled individually. Users can select specific scents, adjust intensity, and set operating schedules for each unit separately. Multi-Device Network: Multiple diffusers can be connected to a single control interface, enabling coordinated control of an entire network of scent diffusers. This allows for creating complex scent displays where different scents are active in different locations simultaneously. Scent Selection Interface: The control interface provides a scent selection system that allows users to choose which essential oil or scent profile to activate in each diffuser. This customization capability enables creating personalized scent experiences. Centralized Control: A central control terminal or application can manage all connected diffusers, providing a unified interface for monitoring status, adjusting settings, and coordinating operation across the network. This modular architecture provides flexibility in deployment, allowing systems to scale from a single diffuser to networks of multiple units, each contributing to a larger scent display experience.

The development process involved several stages of testing and refinement: Bluetooth Connection Testing: Initial testing focused on establishing reliable Bluetooth connections between the control interface and the scent diffuser units. This involved testing connection stability, range, and data transfer reliability. Control Interface Development: A control terminal was developed to provide an interface for managing the scent diffusers. The interface allows users to connect to devices, select scents, adjust settings, and monitor status. Multiple Device Coordination: Testing with multiple Bluetooth devices verified that the system could handle multiple simultaneous connections and coordinate control across a network of diffusers. Ultrasonic System Verification: The piezo disk vibration system was tested to ensure it operates correctly at 108kHz and produces consistent mist output. This involved verifying the drive circuit, frequency stability, and vaporization efficiency. Integration Testing: Full system integration testing verified that Bluetooth control, ultrasonic vaporization, and scent dispersion all work together seamlessly to create the desired scent display functionality.

The essential oil customization system enables creating personalized scent displays: • Scent Selection: Users can choose from different essential oils to create various scent profiles, from floral to woody to citrus
• Intensity Control: The system allows adjusting the vaporization intensity, controlling how much scent is released into the air
• Timing and Scheduling: Users can set schedules for when scents are active, enabling time-based scent displays
• Multi-Scent Coordination: With multiple diffusers, different scents can be active simultaneously in different locations, creating complex scent landscapes
• Real-Time Adjustment: Bluetooth control allows real-time adjustment of scent settings, enabling dynamic scent displays that can change in response to user preferences or environmental conditions This customization capability transforms the scent diffuser from a simple device into a creative tool for designing scent experiences and displays.

Modular System Setup

Modular scent diffuser system setup showing multiple units that can be controlled independently or as a coordinated network


Modular system setup with scent selection interface, demonstrating the customizable scent display capabilities

Bluetooth Control Interface

Bluetooth control terminal interface for managing and controlling the scent diffuser network

Bluetooth Networking Tests

Bluetooth networking test showing connection status with light indicator on the Xiao microcontroller

Scent Diffuser Control Testing

Testing the scent diffuser control system with the Xiao microcontroller, verifying Bluetooth communication and device control


Testing multiple Bluetooth-controlled scent diffusers simultaneously, demonstrating the network's ability to coordinate multiple devices

This week focused on networking and communications through the development of a Bluetooth-controlled scent diffuser system. The assignment demonstrated how wireless networking can transform a simple device into a networked system with remote control capabilities and multi-device coordination. Working with Bluetooth networking provided valuable experience in implementing wireless communication for embedded systems. The process of configuring Bluetooth connectivity, developing control interfaces, and testing multi-device networks required understanding both the hardware and software aspects of wireless communication. The ability to control multiple diffusers from a single interface opened up possibilities for creating coordinated scent displays. The ultrasonic vaporization technology using the 108kHz piezo disk was a fascinating aspect of this project. Understanding how ultrasonic vibrations can efficiently convert water into vapor without heating demonstrated the power of precise frequency control in creating physical effects. The integration of essential oils to create customizable scents added a creative dimension to the technical networking work. The most significant learning was understanding how Bluetooth networking enables both individual device control and coordinated network operation. The modular system architecture allows the system to scale from a single diffuser to networks of multiple units, each contributing to a larger scent display experience. This flexibility demonstrates how good networking design can support both simple and complex use cases. The challenges of Bluetooth connection stability, multi-device coordination, and ensuring reliable communication highlighted the complexity of wireless networking systems. However, the ability to control devices remotely and coordinate multiple units makes these challenges worthwhile, enabling the creation of sophisticated networked scent display systems. The customizable scent display capabilities, enabled by essential oil selection and intensity control, transform the technical networking work into a creative tool. Users can design personalized scent experiences, coordinate multiple scents across different locations, and create dynamic scent displays that respond to their preferences. This week's work emphasized how networking is fundamental to modern connected devices. The Bluetooth-controlled scent diffuser demonstrates how wireless communication can enhance user experience, enable remote control, and support multi-device coordination. Understanding networking protocols and implementation is essential for creating devices that can participate in larger systems and provide enhanced functionality through connectivity.

Note: This assignment documentation website was created with assistance from Cursor AI.

3D Model - Scent Hardware Rack (.stl)
3D Model - Scent Hardware Rack Fusion 360 File (.f3d)
ESP32 BLE Server - Arduino Code (.ino)
Computer Client - Python Bluetooth Control Script (.py)

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