This is an open source, programmable mist maker built as an expansion board for the Seeed Studio XIAO ESP32-C6. It mounts directly on the XIAO or QT PY, is powered over USB-C, and turns a piezo atomizing disc plus any small container into a mist device you control from code or your phone. This XIAO Extension version was designed from the ground up in KiCad 10 this year, and the whole project is Open Source Hardware certified (OSHWA US002742).

Why we made it

Almost every mist maker circuit online is an undocumented black box. This project fills that gap with tested reference circuits, full KiCad sources, an Arduino library, and honest notes about what went wrong along the way. It started by reverse engineering cheap commercial humidifier boards, then rebuilding them as clean, hackable, documented hardware. Built by shuang cai and David Yang.

How it works

The ESP32-C6 outputs a 108.7 kHz PWM (the disc's mechanical resonance) at up to 50% duty. A UCC27511A gate driver switches a logic-level power MOSFET that drives a 3-leg tapped inductor in a loop with the piezo disc. LC resonance plus the inductor's autotransformer action (roughly a 28 uH to 800 uH tap) boost the 5 V USB rail to the ~80 Vpp the disc needs.

An INA180A3 current-sense amplifier (100 V/V) reads a 30 mOhm shunt at 3.0 V per amp. No disc, a dry disc, and a disc in water each draw a different current, so one ADC pin gives you disc-presence detection and a water-level sensor for free. USB-C powered, no battery or boost converter on this board, which keeps it the simplest board in the family. The I2C bus (D4 / D5) is broken out for your own sensors. The piezo disc is a micro-perforated atomizer: a cotton wick feeds water to the back, and each oscillation at 108.7 kHz pumps water through microscopic holes as a cool, room-temperature mist.

Pin map

D0 (MIST_PWM_3V3): 108.7 kHz PWM to the gate driver

D2 (CS): INA180A3 current sense, 3.0 V per amp

D4 / D5 (SDA / SCL): I2C breakout, free for your sensors

Firmware

Flash the ExtensionKit_BringUp sketch to verify the board feature by feature, then use the MistMaker Arduino library (v1.1+):

#include <MistMaker.h> // Select the board variant MistMaker 

mist(MistMakerExtensionV01());

void setup() {
 mist.begin(); 
} 

void loop() { 
  mist.setLevel(180); // 0 to 255: PWM duty sets mist strength, like a dimmer 
  delay(5000); 
  if (!mist.waterPresent()) { // current-sense water check 
    mist.off(); 
  } 
}

Files and links

Docs: docs.byproductlab.com

Source (KiCad, firmware, library): github.com/Dav1dyang/Programmable-Mist-Maker

OSHWA certification: US002742

Safety and care

Water plus electronics plus time equals biology. Use distilled or clean tap water, clean the container regularly, and let the cotton wicks dry between uses. Never run the disc dry (it can overheat) and never drive the circuit without a disc attached (the MOSFET can overheat).