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Thread: Bat detector

  1. #201
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    Hi CorBee,

    The purpose of my developments is slightly different. I go to different people in France who study bats and they face hardware problems. Finance is becoming scarce and the equipment remains very expensive. Or, they have needs that do not exist such as accurate species monitoring. It is with this in mind that I started the development of detectors with the provision of a manufacturing files and setting up participatory workshops. In this context, I developed the following detectors:
    - RhinoLogger to monitor the activity of the bands of Rhinolophus, mainly ferrumequinum. About 40 devices were built at several workshops and they equip sites in western and central France. With Passive Recorder, this device will now be used for this type of study.
    - PiBatRecorder, a recorder for active Heterodyne listening and passive recording. Built with a Raspberry Pi A + card and an audio card the sampling frequency was only 192kHz. We built 12 copies before the audio card was no longer available. As a result this project is abandoned.
    - Passive Recorder, based on the Teensy 3.6 card, offers up to 500kHz sampling frequency and, in addition to the classic passive recording, offers recording modes specific to the Vigie-Chiro project. About 55 copies exist today, at least 20 in Germany and 35 in France (the last 10 built yesterday during a workshop) and I still have 3 workshops of 10 copies planned by the end of April. Given the price (105 €), demand is strong. The main brake is to come to manufacture in the FabLab at Chemillé in Anjou (near Angers). Several projects are trying to carry out workshops elsewhere in France but, for the moment, only Frank has succeeded in Germany (naturalists are not technicians). I do not despair that some people, after participating in one of my workshops, can reproduce elsewhere.
    - Bat Player, an ultrasound reader based on the Teensy 3.6 card. It allows replaying wav files recorded with other recorders. It is intended for debugging and verification of recorders, assisting with acoustic training or bat animations. 15 copies exist, 12 of which were made during a workshop and one by Frank in Germany. It is essential for the development of my detectors.

    I have heard at least 1 copy of these devices but I do not use much, except for the development. They are mainly used by amateurs or professionals. Consequently, except for the RhinoLogger, they must respect the method used in France for the acoustic identification developed by Michel Barataud in his book "Ecologie acoustique" which is the bible in France for this type of study.

    Regards,

    Jean-Do.

  2. #202
    Senior Member CorBee's Avatar
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    Hi Jean-Do,

    We have one common goal, make studying bats with detectors easier. I was on the path of the piBatDetector also but the moment I had time to build that the audiocard was gone. I am happy it did ... that way I kept looking around and finally found the work Frank had done allready. I am mainly working on the software as my hardware skills are limited, I have build several heterodynes in the past but cant handle tiny components like some of you do

    I am currently changing the code I have worked on last autumn to become easier to use, that work will be mainly on the menu and the way you can make selections etc. But I do have plans to improve the auto_TE part of the detector further.

    regards
    Cor

  3. #203
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    Hi Cor,

    Concerning the management of modifiers of parameters and modes of operation, I realized a library which allows me to manage this part very easily. It is Teensy and ESP32 compatible. It normally handles any type of screen but I tested only on 2 OLED types 128x64 pixels. I have not published it yet but I will do it soon.

    For Surface Mounted Components (SMD), I had no skill ... before trying! Unfortunately, we are forced to use them, the classic components being rare for some.
    And, in fact, while remaining within reasonable dimensions, it's quite easy to solder, even MEMS microphones that have an unreachable solder (between the component and the PCB), are quite easy to solder with an air soldering iron as explained in the document "FabMicroMEMS.pdf". I just tested the assembly of a new MEMS found by Frank and the technique works.

    Concerning live auto_TE listening, I am not convinced by this technique that I have experimented with an EM3+. It's already complicated at home in front of the computer (especially me with my old ears), so I prefer the heterodyne which gives an idea of the species and allows to decide if the operator must register it for subsequent analysis. Of course, I only ask to be contradicted!

    I prefer to test automatic determination methods to either memorize the activity as on the RhinoLogger with easy-to-determine species, or trigger recordings on suspicions of species to target particular species. I think the future is for this type of recorder that allows long poses (several weeks to several months) to sample at length certain species and thus facilitate studies of behaviors. And this type of recorder does not present a sufficient market for interested professional builders.

    Regards,

    Jean-Do.

  4. #204
    Senior Member CorBee's Avatar
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    Hi Jean-Do,

    I suggest just trying the Auto_TE the current setup can deliver. I can walk through my garden listening to several species of crickets and suddenly notice that a bat is flying around. Alternatively on a holiday location I suddenly realized that there were not only two different bats flying around but they were also different species as the audible clicks where very different and easy to distinguish in auto_TE. Next step then was to record them and look at the real data. Auto_TE is not necessarily the best instrument to detect/identify (you can even miss temporary clicks) but it can be helpfull and for new-bat enthusiasts it brings more information than listening to clicks. Its more like listening to birds, there songs are very different but if you were to only look at their silouet (never tried heterodyne on them they are more difficult to distinguish. But this is my view after playing around with this for some time.

    regards
    Cor

  5. #205
    Junior Member Polly's Avatar
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    Hi All,

    I've been directed over here by Paul and defragster https://forum.pjrc.com/threads/55386...osteoarthritis. I'm trying to do something similar but also completely different for my PhD. I'm trying to detect the ultrasound produced in knees when moving to predict whether a knee has osteoarthritis.

    I'm trying to learn to code (I've only used matlab before for signal processing) and also get my filtering and amplification right before my signals reach the teensy (3.6). What I want to do I don't think is as complicated as what you are achieving with the Bat Detector! All I want to do is put the signals through an ADC conversion and write them to the SD card in an accessible format for processing later.

    I know what I want to achieve but I'm struggling to figure out how to do it!

    My signals will be filtered to be between 20kHz to 300kHz and amplified to be 0 to +3V.
    I need the sample rate to be as fast as possible, but a minimum of 1.8MHz would be best, I can't seem to find a straight answer on how fast this actually is capable of going but my supervisor seems to think it'll be ok
    I'm going to use a trigger for recording but want to record a small amount of signal before the trigger is tripped.
    Once the trigger has started recording it will record I think for a set time period and stop, but I'm not sure yet.
    BUT I don't know whether it would just be better to record a full 10s activity as one file and do a tonne of post processing to look for hits and waveforms.
    I'm thinking that the best file for me to write to the SD card too will be a .csv with a column for time and and column(s) for the signal.
    I'm also not sure of the data transfer rate of SD cards.

    As you can see, I'm a bit lost so any help/ideas/suggestions would be greatly appreciated!

    Best Wishes Polly

  6. #206
    Senior Member DD4WH's Avatar
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    Hi Polly,

    I do not think that it is possible to record ultrasound files to SD with a sample rate of 1.8MHz with the Teensy 3.6 . . .

    We use a maximum sample rate of 500kHz with 12bit resolution (internal ADC) and that is quite fast already.

    The other solution with the audio board is used with sample rates up to 352kHz for the codec. And that is already a multiple of the allowed spec of the codec. Also not anything near 1800kHz !

    Why would you need 1.8MHz if you have signals that range from 20-300kHz and are already nicely filtered by an antialias filter, as you say? I would say that a sample rate of a little bit more than 600kHz would be sufficient in that case ?

    Have a look at the search function of the forum for your questions on speed of SD recording.

  7. #207
    Junior Member Polly's Avatar
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    Hiya,

    Sorry typo 1.2MHz, still fast though!

    No, this is what I am worried about, and as I've not really had to do anything like this before it's almost like I don't even know the search term required. I am learning A LOT though, so that's a bonus.

    I have been told by colleagues, that I should be aiming for 3 or 4 times the highest frequency (which is where I get the 1.2MHz), they are worried that I will lose so much of the signal if I go to just double, even though it should be fine with Nyquist, I again am not sure about this, but typically on the static systems they use they tend to capture lots of data and then get rid of lots (I believe).
    I just want to look at when we get a waveform in comparison to the gait (walking) cycle.

    Thanks for the speedy response

    Polly

  8. #208
    Senior Member+ Frank B's Avatar
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    There are new 64MBIT (8 MBytes) SPI PS-RAMS - It should be possible to use such a RAM as fast buffer, before writing to the SD Card.
    I have some of them on my desk, since yesterday. Could not do much more than a quick test so far, all I can say is "it will work with a Teensy". I think, with one or two of these chips, it will be much easier.

  9. #209
    Senior Member+ defragster's Avatar
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    Quote Originally Posted by Frank B View Post
    There are new 64MBIT (8 MBytes) SPI PS-RAMS - It should be possible to use such a RAM as fast buffer, before writing to the SD Card.
    I have some of them on my desk, since yesterday. Could not do much more than a quick test so far, all I can say is "it will work with a Teensy". I think, with one or two of these chips, it will be much easier.
    Frank - those 8 MB RAM's are the same outline and pinout as the FLASH chips that worked with your prior PCB's? That would be single SPI access - not quad?

  10. #210
    Senior Member+ Frank B's Avatar
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    yes.
    They can work in both modes.

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