After writing about ESPHome projects for what feels like an eternity, there is finally one with a creative name: The MIST-O-Matic 3000. This fun little device is exactly what you’d expect it to be: A smart, Wi-Fi connected humidifier. At the heart of the MIST-O-Matic 3000 is the beloved LOLIN (previously WEMOS) D1 mini (official AliExpress store) running firmware built using ESPHome. And it wouldn’t be an ESPHome project without any RGB illumination, right? To solve that problem, a NeoPixel Ring with 24 WS2812B LEDs is built into the base.

The MIST-O-Matic 3000, a smart and Wi-Fi connected ultrasonic humidifier

Different to many of the other projects I’ve featured in the past, this one started as an attempt at reverse engineering an existing humidifier. That however turned out to be too complicated due to the use of a custom controller. In the end the easiest option for the creator of this ESPHome project was to build the whole thing from the ground up using parts from AliExpress and our favourite Swedish furniture store, IKEA.

Parts needed for the smart and Wi-Fi connected humidifier

Besides the aforementioned LOLIN D1 mini, the smart and Wi-Fi connected humidifier needs a number of various parts. The mist is created using an ultrasonic humidifier. These use high-frequency sound vibrations to produce what is essentially very fine water mist. Unlike with an evaporative humidifier, there is no heat involved, as there is no need to boil any water for the mist. The ultrasonic modules can be found for little money on many online marketplaces, such as AliExpress.


To move the mist out of the container and in to your space, a small blower-type fan is used. This fan blows air in to the container so that the mist has only one place to escape: The opening in the top. To prevent the humidifier running out of water, a floating water level switch is placed in the water. These turn on or off, depending on how high the water is.

As you might have already guessed, this project uses multiple 3D-printed parts. Namely, the base and its cover, the diffuser base, the top cover, and the water level sensor. In the base there are also two buttons for manual control: One controls the humidifier and the other the LEDs.

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How the smart and Wi-Fi connected humidifier works

The wiring might look rather complex at first sight, however it is easily explained. The power supply for the Wi-Fi connected humidifier provides 24V, which is what the ultrasonic humidifier and the fan need. To not destroy the ESP8266 board and LEDs, .

The schematic for the smart and Wi-Fi connected humidifier using ESPHome

The fan and the ultrasonic humidifier do not have variable levels of operation. They are either on or off. To allow the ESP8266 board to toggle them, two TIP120 NPN transistors are used. The buttons and the water level switch are attached as you would attach any button.

How the smart and Wi-Fi connected ultrasonic humidifier could be improved

In my eyes, this ESPHome project is missing a humidity sensor. Using such a sensor, the whole thing could be configured to turn on whenever the humidity reaches a certain level. Then again, it might be better to measure the humidity at the other end of the room, to see how well the humidifier is performing.

While the exterior of the smart ultrasonic humidifier does look very clean, it could further be improved by using a capacitive touch switch. Though I can’t be sure these wouldn’t be triggered by the ultrasonic module.

Of course, you also have the option to build a larger smart humidifier. All you need is a larger water container and multiple ultrasonic modules.

Liam Alexander Colman, the author and maintainer of Home Assistant Guides.

About Liam Alexander Colman

Liam Alexander Colman has been using Home Assistant for various projects for quite some time. What started of with a Raspberry Pi quickly became three Raspberry Pis and eventually a full-blown server. I now use Unraid as my operating system and Home Assistant happily runs in a Docker container. My personal setup includes many Zigbee devices as well as integrations with existing products such as my Android TV box. Read on to find out more on how I got started with Home Assistant.

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