Sensing Motion with Piezoelectric Sensing: Tips & Tricks

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Discussion Overview

The discussion centers around sensing motion, specifically speed in one direction, using piezoelectric sensing methods. Participants explore the feasibility of using homemade solutions, such as piezoelectric crystals or buzzers, and consider alternative approaches to measure motion without requiring high accuracy.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Meereck inquires about sensing speed using piezoelectric sensing and expresses a desire for a low-cost, homemade solution.
  • Some participants clarify that piezoelectric sensors measure acceleration rather than speed, raising questions about their effectiveness for constant speed motion.
  • One participant asserts that it is impossible to detect uniform motion without external references, such as GPS, while noting that accelerometers can measure changes in speed through integration.
  • Concerns about the cost of accelerometers are mentioned, with some suggesting that individual chips are affordable, but complete modules may be pricier.
  • A creative alternative is proposed involving a string and a bell to indicate movement direction, which some participants find appealing as a low-cost solution.

Areas of Agreement / Disagreement

Participants generally agree that piezoelectric sensors measure acceleration rather than speed, but there is no consensus on the best method for sensing motion in one direction or the cost-effectiveness of different solutions.

Contextual Notes

Participants express uncertainty regarding the limitations of piezoelectric sensors for measuring speed, particularly in scenarios of constant motion. The discussion also highlights varying perspectives on the affordability and practicality of accelerometers versus alternative methods.

Who May Find This Useful

This discussion may be useful for hobbyists, DIY enthusiasts, or students interested in motion sensing technologies and low-cost experimental setups.

meereck
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Hello, I would like sense motion (speed) only in one direction. I don't need it to be accurate, I just want it to be a cheap solution (homemade).
I googled something about piezoelectric sensing with the help of a normal crystal (or piezo buzzer?).

Does anyone have more details on that?
Can I sense speed with it?
Thanx for hints,
Meereck
 
Engineering news on Phys.org
hello, thanks for the links.
It measures acceleration not speed, right. So If I move it at a constant speed, it will not work? Am I right?
Furthermore, I reckon it is quite expensive, isn't it?
cheers
 
meereck said:
So If I move it at a constant speed, it will not
cheers
No, it is impossible to sense that you are moving if the motion is uniform (this is one of the basic principles of physics) UNLESS you somehow use information from the environment, the most obvious example being a GPS.
However, if you have an accelorometer you can always tell when/how much your has speed changed and by integrating you get the speed.

Accelerometers are not very expensive nowadays, an accelerometer chip is only a few dollars. However, if you need a complete module it will obviously be more expensive.
 
Get a length of string, and a bell. Tie the string to whatever you want to sense the movement of, and tie the bell to the other. When the bell rings, your subject has moved. If your subject moves in the other direction, the string goes slack and the bell won't ring.
 
f95toli : thnx
brewnog : that is the cheapest solution. Pretty cool!:)
 

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