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I guess it depends how reliable it needs to be. If we must never exceed a fixed limit (e.g. if there is a fixed in-memory buffer limit) it would be better to dynamically partition the files. By that I mean, do not have a fixed time cut-over, instead start a new folder when the old one is full...

Hi Cor, Does the existing SD Library (or the new one) support the use of folders? If so, you could just store the list of folders and the contents of the current folder in RAM. For example if you set the limit to 200 (folders and files) you could save 40,000 files but still only need to keep...

That is an interesting paper. It gives rise to another enhancement request, as well as the stereo microphones, could stereo cameras be added with a 20-30Hz strobe trigger for a bank of flash guns? (Sorry, I know I am a day late for jokes!)

Many thanks Edwin, those answers make a lot of sense and I hopefully understand better how everything works. The comment about the sound pressure generated by a bat was just to highlight how impossible it is to work from the mic sensitivity figure. (Although I was not expecting an answer, it is...

No matter what I try, I cannot generate any signal through the microphone. (I can inject noise by touching various parts of the mic board.) That makes me think my initial guess that I broke the microphone was correct, so I have ordered a couple of replacements from Edwin. While waiting for them...

Sorry for the confusion, when I said "I hear nothing" I meant apart from noise. No signal from and sound or ultrasound I can generate. I'll try harder tomorrow, but tested quickly just now. With the mic attached, gain 30, there is gentle white noise and touching the AF in on the audio board...

Looks like that did the trick, as I now have some signal displayed, if I turn the gain up over 50. However, I hear nothing. (Tried rubbing fingers and jangling keys. I even tried gently rubbing the top edge of the mic board - as I thought that would be guaranteed to generate something.)...

I put an oscilloscope across the AF in on the audio board and touched the middle pin on the mic board and could see some nice noise ~1v peek to peek (not 0.2v as originally states, as someone had forgotten how to use the 'scope!). I assume that signal is large enough! (Jangling keys gives a...

Thanks for the suggestions, Edwin. The results are: Playing WAV file shows as expected in display (waterfall) and audible in headphones 3.3v good (well, 3.2v but hopefully close enough) both where you indicated and on the mic board Touching the mic (middle) pin produced no display Touching the...

That sounds like a good place for me to start! Do you know where I can find a suitable file? (If you have one you don't mind sharing, you could upload it to your GIT repo, with test instructions.) -- David

Thanks CorBee. You asked for software improvement suggestions before, perhaps a [self] test option, if you hold down the right push-button during power-on (like the reset option). Not 100% sure what exactly it would do, but could cycle through everything (encoder up/down/press, push-buttons)...

Some good news, after some shipping delays and illness, all the parts have arrived and have been put together and it turns on, can be programmed and even has a nice display. Not so good news is the actual bat detection bit does not work! In either spectrum or waterfall mode nothing is displayed...

For now I just plan to build the detector, but I will probably add some extra headers, so I can experiment when I have more time (probably next winter). A plug in Bluetooth audio transmitter may be a good initial addition.

That sounds interesting. I have been thinking about this while waiting for all my parts to arrive. Are you using a module like HC-05/06? I was wondering about using an ESP32 as a co-processor (it would relieve the teensy of extra load - I assume it is very busy with the DSP - and has WiFi as...

Thanks Edwin. That worked better. Your parts list has LP2950Z which produced no hits. I'll see is I can order the rest of the parts tomorrow and see if I can beat the bats.

Sorry I am so late to this party, but I only accidentally discovered this project last week. Actually, I was possibly too early as I had an idea to build a similar bat detector with FFT & frequency spectrum display, as an interesting project to use the Arduino Zero when it was released (2015)...