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Ultrasonic Wall of Sound

Julf

Facts are our friends
Winter is coming, so rodents try to move indoors. As I was thinking of how to discourage them, I came across some piezo tweeter horns being dumped really cheaply (less than € 2.50 each). Add a surplus class D amp and a Raspberry Pi, and you have the Ultrasonic Wall of Sound.

Finally a valid use for a 96 kHz sample rate.

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Hmmph... Seems the forum doesn't grok Google Photos. Here is a link:

https://photos.app.goo.gl/2yUkFdTbc3j6H4DS2
 
It does - you just have to use the link to the original large images and the insert image button. The images are rather large though


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What's the capacitance of one piezo unit, Julf?
With that much 'C' as a load, if you couldn't just use a mosfet and small inductor or two off the supply, and just do away with the rasppi and amp: free-running ultrasonic power oscillator.
 
What's the capacitance of one piezo unit, Julf?
With that much 'C' as a load, if you couldn't just use a mosfet and small inductor or two off the supply, and just do away with the rasppi and amp: free-running ultrasonic power oscillator.

One unit is something like 0.13 uF. Pretty sure the commercial rodent repellent devices use a simple circuit, but I like the fact that I can make the signal more complex (random, dissonant frequencies at random intervals).
 
..until you get bigger, harder rats coming round demanding you play them nosebleed techno...

Uh oh - I already ensured the signal was dissonant and random to allay the concerns my wife had that I might end up as an (electronic) pied piper of Hamelin...
 
Obviously this will only work for young rodents, the older ones will not know what the kids are complaining about.
 
These cheap piezos are widely sold in SE Asia to attract cave swiftlets. People "farm" them in shoplot roofs for the edible (and expensive) nests
 
Isn't this what the Americans accused the Cubans of doing at the American embassy in Havana, if so I'm sure the Cubans were only trying to get rid of any rats :)
 


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