MIST MAKER
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.
How do you find out the resonance frequency of an “unknown” ultrasonic transducer?
An ultrasonic transducer is a lump of metal and ceramic that has a particular resonant frequency. To operate the transducer at resonance, it must be driven with a high-frequency AC signal. The best way of determining the resonant frequency is to plot an impedance spectrum of the transducer. Anyone interested in taking part can get in touch with me through the comments box below. Engineers always want things not to be good but to be perfect every time! This is usually done with very expensive network analyzers, but it can also be done with a simple USB oscilloscope and sweep frequency generator if the oscilloscope software has suitable capabilities.
For a very quick in-lab experiment, just omit 78L05 and MC34063 ICs from the circuit. Then power up the oscillator circuit (NE555) from a regulated 5-Vdc power supply and use regulated 20/24/26 Vdc for feeding the driver circuit (IRLZ44). You will need a dual-channel lab power supply to proceed with the minimal lab test setup.