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Everything posted by svorkoetter

  1. Indeed, the piezos that I used when originally developing Watch-O-Scope uses piezos taken out of a greeting card's speaker as their microphones.
  2. What I find interesting is to ask questions about the circuit with only a circuit board layout instead of an actual schematic.
  3. You quoted my entire original post from 6 years ago, pictures and all, to add this (incorrect) bit of information?!? Hint: I've been a professional software developer for 31 years. https://lmgtfy.com/?q=featuritis
  4. Hi @MatteoB, this forum probably isn't the place to get into such details, but very briefly, the input is first filtered (if filtering is enabled) using a 4th order infinite impulse response bandpass filter. After that, the software tracks an envelope of the signal, looking for the three distinct sounds making up each tick (as mentioned by @guidovelasquez). The time of the start of each sound is recorded, and the watch performance computed from those. Statistical analysis is applied to all the ticks within the averaging period. This, together with the initial filtering, is what produces stable
  5. There's a big difference between a preamp and a headphone amp. In the simplest terms, a preamp takes a very weak signal (or in the case of a watch mic, a very very very weak signal) and turns it into just a weak signal. A headphone amp turns a weak signal into a strong signal. Amplifiers also do impedance matching. A piezo element's impedance is primarily capacitive (around 27pF for the one I use), whereas a sound card's input impedance is resistive, typically around 10kΩ. A suitable preamp has corresponding input and output impedances. A headphone amplifier on the other hand takes a sign
  6. Yes, you can just download the new version and it will update your installed version without messing up your license.
  7. Hi All ... I just wanted to let you know that I've just released Watch-O-Scope 1.3, with the following improvements and new features: Built-in volume boost, adjustable via scope and manual adjustment modes, requiring less external amplification. Long term test improvements: Ignore extreme outliers (±4σ) for better immunity to non-timekeeping noises (e.g. the date wheel clicking over at midnight, doors slamming, cars crashing outside). Clip graphs to three standard deviations (±3σ). Highlight one standard deviation (±σ). Support for manually selected beat rates
  8. So far, the kit that Eland posted seems to be a good option for someone who doesn't want to start from scratch. I will pick one up when I'm in Germany later this month, and give it a try. The thing I like about it is that it doesn't use a proprietary part. The LF351 is generic, has multiple sources, and has been around for a long time. I just haven't had any experience with it before now.
  9. Yes, so long as neither the input (not likely) nor output signal is more than about 2V peak-to-peak.
  10. The gain of that circuit is only about 100 (40dB), which probably won't be adequate, and despite what the manual says, it won't run off of 3V. At 3V, the input signal is biased at 1.5V, which is of course only 1.5V below the chip's supply voltage, a point above which it will not operate. Put another way, there is zero headroom if operated at 3V. The only thing it will amplify without severe distortion is total silence.
  11. Unlike a capacitor microphone, a piezo doesn't need a power source. And a dynamic microphone is a power source.
  12. I agree with JerseyMo in principle, but of course those aren't the rules here. However, I don't see how buying a cheap knockoff piece could be "too cheap". You have a cheap knockoff watch, so why would that be any different than the original missing piece? A real Rolex piece would indeed be expensive, they won't sell you one anyway, and it probably wouldn't fit.
  13. That contact mic is a piezo, and is also known to work. However, it's not very practical for working on an opened watch. The brass pin idea is sort of what we already use, except we use a pin attached to the watch movement (more commonly referred to as the winding stem and crown). It might be worth trying to cover the piezo disk with foam though, leaving a hole for the crown to go through.
  14. Those bimorph sensors are the ones I was referring to. I may try just gluing one to an alligator clip to see if that works.
  15. An actual vibration sensor, as discussed somewhere earlier in this thread, and of which I've ordered some but not yet used, would probably work even better. Guido, I wonder if your sensor would be improved by cutting down the piezo disc into just a strip?
  16. Hence the smiley in my post. If it's a lapel mic, it's not a piezo. It's an electret condenser mic. These have a built-in preamp. We tend to avoid those because they have DC current running through them, and could, in theory, magnetize your watch.
  17. Are you sure you were using a piezo mic? If a piezo mic clips on your PC's input, a regular mic would blow up the computer. Yes, WOS will work with USB audio devices. If the device is visible to Windows, WOS can use it.
  18. Yes. A piezo microphone produces a much lower signal level than a condenser mic, on the order of microvolts. Very few sound cards work with such low levels, even if they have a dedicated mic input (which most laptop sound card inputs actually are). Some amount of amplification is needed for a mic input, and even more for a line level input.
  19. Guido is right. If you are denting the piezo without the plastic there, then you are pressing the watch too tight against the piezo.
  20. The resonance is probably caused by a combination of factors. Perhaps with some watches, the yellow plastic dish vibrates against the plastic of the watch holder? I would suggest removing that dish entirely, since its shape will cause echoes, and the edges can easily vibrate.
  21. From the pictures, I suspect that the resonance you are getting is physical, not electronic. That yellow plastic around the microphone might be resonating, or whatever is behind it might be. Did you use a bare piezo element, or is it enclosed in some sort of plastic housing. If it is enclosed, _that_ might be resonating.
  22. I just ran your echo recording through a spectrum analyzer, and the buzzing echo sound is at 581Hz and multiples thereof. The peak is at the seventh harmonic and it goes down from there in both directions. That's the same sort of spectrum a bowed string instrument has, so there's probably something thin resonating in your watch microphone or stand.
  23. The resonance might be in your microphone stand. If the stand is not good and solid, it might resonate at certain frequencies.
  24. Maybe something is resonating? Is your watch microphone stand good and solid?
  25. I just listened to your recording, and it sounds to me like your laptop's microphone is still on too. Which audio device have you selected in Watch-O-Scope's settings window? If it is Microsoft Sound Mapper - Input, then make sure all other microphones are turned off via the Windows control panel. Alternatively, you may be able to select just the correct microphone in Watch-O-Scope.
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