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Thread: Bat detector

  1. #526
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    Quote Originally Posted by aethertech View Post
    What is your ultrasound application?

    at
    Passive Acoustic Monitoring (PAM) on underwater glider (6-channel volumetric array)

  2. #527
    Quote Originally Posted by WMXZ View Post
    Passive Acoustic Monitoring (PAM) on underwater glider (6-channel volumetric array)
    I am imagining a boat, open water, sunshine and sun block. Must be fun...

    Can I assume you are monitoring biological sources? Do you do any spatial processing as well?

    What sort of hydrophone are you using?

    Awesome...

    at

  3. #528
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    Maybe people think we might still be struggling to get the device working properly. This is not the case, we are just looking to get it to work even better than it already does.

    The next path was investigating how much we could gain by not using mic-in but using line-in instead, so I did some experiments.


    I tied some tests with a tone ladder injecting signals on mic in and line in at 0, 10 and 20db
    I did not really see any difference, just one important difference was noticed. When ik signal generator was disconnected the noise level dropped after a few miliseconds. Looking like some "mute" function on the line input.

    After these tests I wanted to confirm what I found on a bat recording so I set op my dac and speaker and recorded using the SPU microphone and amplifier in the style I was used to. Amplification was set to 9db for both line-in and mic-in.

    This is an image of two recordings, the upper is on the line in, the lower is mic in.

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    You can see lighter vertical lines at the moments where no sounds are registered, they are similar to the lower noise signal i did see after disconnecting the signal generator in earlier tests.

    I took some spectrum images at different points. This one is the spectrum around the ping at about 0.07-0.08

    Line in
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    Mic-in
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    This piece is the silence between two "pings"at 0.08 - 0.18

    Line-in
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    Mic-in
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    These are the short pings (feeding sounds) at 0.33-0.36

    Line-in
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    Mic-in
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    Somehow the silences seem to be more silent but at the pionts where we are registering some sounds we can see almost no difference in the signals and the noise.

    To me it seems the mic in will get us recordings just as good as the line input.

    Edwin

  4. #529
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    Mic Diff AOP amplifier PCB ICS40740 40730

    After many weeks I try my small pcb with simple differential amplifier: Betters resuls for spurious at 27Khz.SMD small form-factor PCB: can be added to the input connectors.Design details*:
    AOP: ADA4807: low cost,low noise,low power,available farnell RS and LTC simulation.
    Gain: about 2 : can be adjust with 2 classical Resistor.
    Some filtering : simple input HPass to reduce intelligible audio voice and other noise.
    Low pass : mandatory for AOP stabilisation, simple first order.
    Differential Impedance seen by mic can be adjusted (750 ohm for this test, very close to ICS 40730 specification )
    I keep the modified single transistor input stage, at the output of this amplifier:I can compare many mic inputs by simple removing the front connector in live.

    Corbee, PE1pwf, if you want one Pcb,ask me. I can also provide some SMD parts for you.

    Design files : Be careful there is a mistake in my PCB, visible in schematic. See easy correction on PCB with through holes resistor. I remove the GBRfile from project

    Next step : Define the optimal impedance and amplitude at the codec line input with correct #define value in code.
    When this amplitude wil be well defined we can increase AOPdiff amplifier gain and remove first stage transistor amplifier.

    I’will also be interested to try the new ICS40740 and look at this 27Khz spurious signal.
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    Attached Files Attached Files

  5. #530
    Senior Member CorBee's Avatar
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    Congrats, good to see you did not give up hope I am interested to see how it works, did you allready try to record some bats ?

    regards
    Cor

  6. #531
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    Last evenings of busy bats, bad computers and struggling with Kicad.


    I think this sums up most of the activity here.
    My computer stared acting up telling me not to shut down but configuring stayed at 100% and did never finish. I don't quite understand why and how but somehow it is running again and I can use it I had some scary moments. Almost considering a new install of the OS.

    This weekend we had some warm evening after a few evening below zero but on these warm nights the bat's came out again and man they were busy.
    They sounded like pipistrellus but I did not check any recordings. This evening is not very cold and I heared one flying by the house again. I hope to be able to monitor te check out some old bridge foundations which were adapted so bats can use it during the winter. It would be nice if they actually start using it.

    Remis, your boards look nice, I just wondered why you are using tru hole resistors for R10 and R11
    I wanted to have a peak at the schematic, and I guess I should just have asked for it. I installed Kicad which took a while and I tried to work with it but I guess I am top much used to working in Eagle. Well I ventually got it to whork and I brushed up the schematic a little and for those that are wondering and did not install kicad yet this is what it looks like.

    Click image for larger version. 

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    I buit something similar but had the feeling I was nog very more pleased with this than with the SPU microphone.
    I did have the feeling that the microphone I was using had a "dip" in the sound registration around 70Khz.
    I wonder how it looks to you and if you had the time to test your bat detector.

    During the time I'm writing this I had seven fly-bys here in the garden.

    Kind regards,

    Edwin

  7. #532
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    Hello Edwin
    20 years ago i worked with my first PC , win, and eagle. Today my choice is: PC , Linux, and first project in Kickad. Easy, enough for our project, long term support. No cost. Kickad work also under win. A lot of shared libs and tutorials. LTC simulation works fine with wine. Arduino works under linux.

    I keep both SMD and trough hole resistor for gain adjustment You can choose. Throught hole technology is more easy to buy, found, and change. You can adjust the gain with same value for R10 and R11. With 5600 ohms the gain is ‘’low’’ and the output is connected to the transistor first stage input, without any saturation effect.

    I don’t see the 27Khz spurious. I hear some bats , but I don’t have enough around me, in this city.I don’t performed enough test to talk about this deep a 70Khz. Spectrum seem to be flat. And previous measurement, without mic, with generator confirm simulation. The High pass filter reduce the noise coming from classical sounds.

    Major interest of AOP in diff mode is the doubling voltage seen at the mic output : both signal are in opposite side. Thus, 6dB improvement. I can also adjust the differential impedance seen by the microphone for investigation. You can have few PCBs (without correction ) if you want.
    Remi

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