Why am I getting a "shark finn"-like signal?

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SUMMARY

The discussion centers on the analysis of a "shark fin"-like signal pattern observed when using a logic analyzer (Seleae) to measure voltage from a triboelectric tapping device connected to an Arduino and a pneumatic pump. Participants suggest that the irregular signal may result from sampling aliasing, noise from USB communication, or grounding issues. Recommendations include providing a schematic of the setup and experimenting with environmental factors, such as adding water to the triboelectric device to alter its resonant frequency.

PREREQUISITES
  • Understanding of triboelectric effect and its applications
  • Familiarity with Arduino programming and interfacing
  • Knowledge of logic analyzers, specifically the Seleae model
  • Basic principles of signal processing and noise analysis
NEXT STEPS
  • Investigate sampling aliasing in logic analyzers
  • Learn about grounding techniques for electronic circuits
  • Explore the effects of environmental changes on triboelectric devices
  • Study USB communication noise and its impact on signal integrity
USEFUL FOR

Electronics engineers, hobbyists working with Arduino, and researchers studying triboelectric effects will benefit from this discussion.

matteo_ianna
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Hello! My collegue and I are having hard time to understand what is happening. Basically we have a tapping device that work with Arduino and a pneumatic pump. The pump allows the tapping of two surfaces which perform triboelectric effect. We are connecting to those a logic analyzer (Seleae), to detect the signal and eventually quantifying the voltage produced. When we do it, we occour in this "shark finn" shape of the spikes, which pattern repeats all the time after n taps (see highlighted area in the picture). Do you have any idea why we are getting this pattern and no constant spikes?

Thank you so much in advance, really!

tribo problem.png
 
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Welcome to PF.

Ca you zoom in more on the signal? It may just be that you are getting some sampling aliasing in the displayed waveform.

Also, do you have a schematic and links to the datasheets for your components that you can share with us? Thanks.
 
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matteo_ianna said:
logic analyzer
What does your (desktop) oscilloscope says?
What's your grounding setup?

Ps.: for me this looks like noise from regular USB communication.
 
Last edited:
Is that trace of
1) one device
1) both of them electrically combined
2) both of the mechanically (acoustically) combined

Try putting a drop of water on one of the triboelectric devices to change its resonant frequency. That may well give clues to the cause.

Post the screen shot here so we can take some more wilda*s guesses.
 

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