Benefits of using a humidifier


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Ultrasonic Mist Maker
I needed a simple mist maker/humidifier for a project that I was working on. I found lots of ideas on the internet, but they all lacked in one area or another, so I decided to design one. The following lays out my easy-to-build ultrasonic mist maker. It works fine and is, by far, the easiest ultrasonic mist maker/humidifier that I’ve ever had to get going.

The misty head
In an ultrasonic mist maker/humidifier (also called an ultrasonic atomizer), a piezo atomizer disc/transducer (ceramic humidifier) works by transposing high-frequency sound waves into mechanical energy that is transferred into a liquid, creating standing waves. As the liquid exits the atomizing surface of the disc, it’s broken into a fine mist of uniform micron-sized droplets, so the key component required for this little project is a particular (20-mm, 113-kHz) ultrasonic atomizer disc/transducer (see below).
When buying the transducer, make sure that is has a 113-kHz (±3 kHz) resonance frequency — another popular transducer has a 1.65-MHz (±0.05 MHz) resonance frequency, which is not compatible with this project!

Circuit diagram of the transducer driver
Below is the circuit diagram of the final part of the project — the transducer driver. As shown in the circuit diagram, it’s a tricky oscillator design based on the ubiquitous tiny time chip NE555P (IC1) to generate proper drive pulse train for the atomizer transducer. In the circuit, the 5K multiturn trimpot (RP1) can be used to set the oscillator frequency to 113 kHz (±5 kHz) (TP1). Even though the ultrasonic mist maker device is configured to run on a single 5-Vdc to 12-Vdc input, this transducer driver needs a 20-Vdc to 26-Vdc (V_DRIVE) power supply channel in addition to a 5-V regulated DC supply rail. So a dedicated power supply circuitry will be introduced later to fulfill that crucial requirement.