EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: brue on March 06, 2012, 10:58:03 pm
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Hi
Im looking for a circuit of an "Bat Detector" who can convert ultrasonic sound in herable frequencies. We want to use it for our rats, they produce ultrasonic sounds as well. (20-200kHz)
I would prefer a circuit without a bandwith selector. Just convert the whole 20-100 kHz to hearable. Knows anyone a circuit?
Thanks
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Unless you have an 80kHz hearing span,you will have to separate the spectrum into useable portions,somehow.
It all depends on what you intend to use it for,
If it is just to detect the presence of the rats,you could find out the dominant spectra in their "speech",make a device tuned to the middle of that frequency range,& then convert this narrower band of frequencies into the audible spectrum.
If rats are anything like humans,their 'speech" is in two parts,--the lower frequency part forms the utterances into 'words" & the high frequency part gives it its character.
If you wish to hear all of this span you are stuck with using some form of tuning.
You could collect the sound with a wideband microphone,feed it into a mixer,the local oscillator of which is located within the frequency region of interest,then feed the resultant difference frequencies into your sound card.
There are several different versions of software which could give you a spectral display of this resultant range of frequencies-----Hams use them for Software Defined Radios (SDR).
The software allows you to "tune" to particular frequencies in this passband,using your mouse.
Of course,to cover the whole spectrum,you would need multiple crystal oscillators.
If you don't mind mixing them all up,you could use one oscillator with a lot of harmonics,but the result would not be very useful.
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20-100khz hearable , use a octave down ?
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This is a favorite project easily googled:
http://pw1.netcom.com/~t-rex/ (http://pw1.netcom.com/~t-rex/)
http://www.micro-examples.com/public/microex-navig/doc/077-picobat (http://www.micro-examples.com/public/microex-navig/doc/077-picobat)
http://www.batmanagement.com/Ordering/acoustic/hardware.html (http://www.batmanagement.com/Ordering/acoustic/hardware.html)
Just a few among so many.
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This was also in Nuts and Volts Magazine June 2011. It was a fairly simple OP Amp based circuit.