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how to make an Ultrasonic Water Fogger for those creepy witch's cauldron effect? Answered

Also known as ultrasonic fogging devices, these consist of metallic plates which vibrates with ultrasonic frequency to nebulize the water molecules to form a vapour which appears as thick low lying fog. For the effect they are simply placed below a water body. Please provide complete details.



 As everyone says, it's easier to buy one than build.  If you want to explore building, google "ultrasonic fogger circuit."  

Foggers nebulize water with piezo transducer operating at ultrasonic frequencies.  The frequencies, 100's to 1000's of KHz, can be generated with a timer IC or crystal, but the problem is to amplify the ultrasound to a power output of several watts.  There is discussion of this on Google.

It's like Lemonie said.  This is one of those artifacts that would cost more in parts, time, and frustration, to build one yourself, than it would to just buy a new one in module form.  

If you want to know how these things work, the best I can do for you is a picture of the inside of an old ultrasonic humidifier. I don't have the picture with me on this computer, but I could find it if you're truly interested.  I  mean what you'll see is the transducer itself, a big beefy transistor, a circuit board, some wires, etc. I'm not sure what frequency they drive it at, or what voltage, how much current, etc. 

As I was saying before, if all you want is the water-fog, without caring too much about how it's made, it's easiest to just buy one of the modules and dunk it in some water, then plug it in.

Also a small air moving fan can be used  to keep the fog from just pooling up in one place.