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Registered Member #621
Joined: Sun Apr 01 2007, 12:37AM
Location:
Posts: 119
I've been wondering about this, I put my finger into a humidifier right above the metal disc that looks to me like a transducer of some sort, like a piezoelectric disc inside a siren, and my finger felt like it was heating up from the inside out! It actually hurt so I pulled it out fast LOL!
How do these things work, do they heat the water or just agitate it, and what frequency do you think it is? It was more like a hiss. Are the dangerous?
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
I had a weird lamp with one of those in it, plus LEDs. I put my hand in the water above the agitator and though i was getting shocked. I think its just a piezo disc in a water proof enclosure, probably anyone here could build one.
It was cool putting a couple drops of red food coloring in the water; see if you can guess what that does...
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
The frequency is in the MHz range. The elements break easily because of the large forces, so if you touch it with something else than water it might get damaged quickly. The lifetime is short even when run in water, after about a year the amplitude should be significantly reduced unless it is running far below the rated current. The drive voltage is often 100V+ so take care when playing around with the driver.
I have heard about people getting something that looks a bit like burns that were quite painful so it is probably not a good idea to keep the fingers very close to the element.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hey, I'm curious about these things.. I never found any real good information about them. From examination It appeared that there is a small, thin piezo speaker like those from toys and singing postcards driven by a little electronic circuit hidden in a box below.
The frequency is in the MHz range.
Are you sure about that? The entire thing just appeared cheap for a circuit that would continuously pump 10's of W at that frequency.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Yes, I am sure. I have seen frequencies between 1 and 3 Mhz, specific for the particular element used. With a resonant element and a prayer the driver probably can be quite simple.
Registered Member #180
Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187
I have one of those in my basement right now that I have been playing with (I'll get pics after work tonight). I wouldn't put your finger in... it hurts quiet a bit. You can even melt plastic with the stream of water that rises off of the element.
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Ultrasonic "fog" makers like in humidifiers
