Check out the GitHub repository for the latest files, documentation, and development updates.

A external enclosure for the ducky mist maker with recycled food container.

Overview

This is an open-source documentation of a low-cost, small-form-factor ultrasonic mist maker. These designs are rarely well-documented online, especially when it comes to understanding their electronics and power needs. This project, created by Shuang Cai and David Yang, aims to make mist-making circuits more accessible for creators, artists, educators, and engineers. By openly sharing tested designs, PCB files, and instructions, we hope to contribute to the open hardware community and enable more people to explore mist as a material.

A close up look of the PCB board design.

A close up look of the wired up PCB board design with piezo disc, inductor, and Xiao MCU.

Project Goals

• Demystify how ultrasonic mist makers work
• Provide a tested, open-source reference design
• Share lessons learned through prototyping and debugging
• Contribute to a more accessible and replicable circuit model

How It Works: Mist Maker Basics

Ultrasonic mist makers operate using high-frequency vibrations to atomize water into a fine vapor. The device integrates multiple subsystems—piezoelectric transduction, voltage amplification, and digital control—to reliably and efficiently generate mist.

A gif of all the work in progress board design for this mist maker project.

Working Principle

1. Ultrasonic Vibration:

   

   An illustrated close up look of piezo disc design from Ultrasonic Atomization Study.

   • The piezoelectric disc resonates at ~108.7 kHz.
   • When driven by a high-frequency signal, it oscillates rapidly, creating ultrasonic waves.
   • Water is pulled through small center holes in the disc, forming a cool mist.

2. Voltage Amplification & Resonance:

   

   An illustrated view of piezo disc water drop formation from Ultrasonic Atomization Study.

   • A 3-legged tapped inductor is used, commonly seen in commercial humidifier designs.
   • This inductor functions as a tapped autotransformer and LC resonator.

   

   An illustrated view of piezo disc driver design from Ultrasonic Atomization Study.

   • It boosts the voltage to the piezo, achieving ~80 Vpp from a 5V input.
   • The alternating voltage amplitude drives the piezo to move.
   • This behavior was confirmed experimentally and aligns with reverse-engineered humidifier schematics and BigCliveDotCom’s teardown.

3. PWM Switching:

   • A logic-level N-channel MOSFET (e.g., AO3400A) switches the circuit.
   • It is driven by an ESP32-C6 GPIO pin generating PWM at ~108.7 kHz.
   • The MOSFET toggles the grounded leg of the piezo-inductor loop.

4. Power Supply System:

   • The TPS61023 boost converter steps up LiPo or USB input to 5V.
   • V1.4 boards also include the MCP73831 for safe battery charging.
   • Reverse current protection and TVS diodes help prevent power path issues from inductive kickback.

5. Physical Design:

   • The piezo is placed inside a water reservoir made from recycled containers.
   • Only the piezo touches water; electronics remain sealed and dry.