45. DIY Zelfbouw Teensybat-VLEN Bat detector/recorder (Vleermuis) Open Source

Samen met Cor Berrevoets heeft Edwin Houwertjes een ‘open source’ zelfbouw vleermuisdetector/recorder ontwikkeld op basis van een Teensy 3.6 developmentboard die ook spectrogrammen weergeeft van de geluiden die je ontvangt. Deze geluiden worden hoorbaar gemaakt in

Heterodyne, Auto Heterodyne, Time expansion.

De Time expansion is min of meer live, de geluiden die je hoort worden afgespeeld in de pauze's tussen de geluiden. Dus geen tien seconden opnemen en dan 100 seconden luisteren, maar direct na een geluid van 4ms dat in 40ms afspelen.
Met het toestel kan je op een hoge samplerate opnemen en kun je hem gebruiken als logger, dus automatisch opnemen (in WAV-file) als er een ultrasoon geluid wordt gedetecteerd.
Het hele apparaatje kost qua materiaal nog geen 150 euro, time expansion was nog niet eerder zo goedkoop.

Cor is de man achter de software, Edwin is van de hardware (printplaat ontwerp) en het verbeteren daarvan en het doen van verschillende tests/upgrades. https://www.youtube.com/watch?v=VdvLUm_KueM

Meer informatie voor het bouwen:

https://drive.google.com/drive/u/1/folders/1NRtWXN9gGVnbPbqapPHgUCFOQDGjEV1q

1. Building Teensy bat detector
2. Handleiding voor de software
3. Manual Teensy Bat detector
4. Microphone enhancements
5. Teensy final.zip
6. Teensybat schematic
7. Ultrasonic test sound
8. Updateing software.pdf

.

Github link naar de laatste software.

Forum link voor discussie.Teensy audio board to higher rates

https://forum.pjrc.com/threads/38988-Bat-detector
PJRC is the fabrikant van de moederboard

With the new possibility to set the sample rate of the Teensy audio board to higher rates, it should be possible to build a bat detector with the Teensy 3.5/3.6. Thanks chip and Pete for your suggestions and Frank B for the higher sample rate possibilities! :-)

Bats use echolocation with ultrasound and use frequencies from** 12 to 125kHz. Most bats, **however can be detected, if you use a sample rate of 192ksps, that means the usable upper limit frequency is < 96kHz, which is quite nice and covers the vast majority of the bat species occuring worldwide (with the exception of most horseshoe bats). [Audio frequencies > 96kHz are very heavily attenuated in the air anyway, so you would have to be very close to a bat calling at 100kHz (a few meters!) to detect it]: --> so, I think a bat detector detecting frequencies < 96kHz is a very useful thing.

It would be very cool, if we could use the** basic Teensy 3.5/3.6 [sorry, probably not possible with Teensy 3.2 and smaller] with its Teensy audio shield plus an electret mic** (those tiny little ones) without further hardware to detect bats!

First, I think, we have to look at some basic questions, before starting to program the Teensy:

the samples come in such a high rate from the audio lib in that sample rate, that we can only do some very light audio processing, we have only (128/192000) = 667µsec for a block of 128 samples. [FFT256point should be possible, but a 512point or 1024point FFT is probably not possible]
Is there an analog anti-alias filter in front of the ADC of the SGTL5000 Teensy audio board? **If yes, we do not need to work any further in this thread, because that would make it impossible for us to process audio > 48kHz through the audio board.
To lower the processor usage, we could do the following: sample at 192ksps, decimate the audio, process the audio, and interpolate.
Zoom FFT: To get high resolution to look at the bat calls, we need many many points in the FFT, > 1024. That is of course not possible in that high sampling rate, even with the fast Teensy 3.6. We could use a technique called Zoom FFT to have a detailed look at only a small portion of the frequency spectrum with a small FFT (say 256 points). **ZOOM_FFT
Before doing all that, a first start could be: get the audio at 196ksps (queue object) --> software DDS or sinewave object with user adjustable frequency (12 – 96kHz) --> multiply that with the incoming audio --> hear batsound at 0-20kHz : that is called a heterodyne detector

What do you think about this? Any answers to the above questions or any further suggestions/ideas greatly acknowledged!

Frank

Last pressentation is in English
Open Source Software
https://www.youtube.com/watch?v=z5C3wLsyGdE&t=47m (OpenSource Introduction)

Software and Bats

https://www.youtube.com/watch?v=z5C3wLsyGdE&t=47m (OpenSource Introduction)
Tadarida Open Software Toolbox
https://www.youtube.com/watch?v=z5C3wLsyGdE&t=59m (English)

DIY Zelfbouw Teensybat-VLEN Bat detector/recorder (Vleermuis) Open Source (45)
https://openresearchsoftware.metajnl.com/articles/10.5334/jors.154/

Publicado el diciembre 19, 2020 08:00 TARDE por ahospers