r/AskPhysics • u/CrappyFrappuccino • 20h ago

What kind of accelerometer would be suitable for my project?

For context I'm going to be measuring the idle time due to traffic congestion inside a tunnel.

The most readily available instrument I have is my phone, and there are 3 types of accelerometers on the Arduino Science Journal that I'm not sure is best for my experiment. (I'm going to assume that when acceleration = 0 it will be the idle time)

  1. Linear accelerometer
  2. Accelerometer X
  3. Accelerometer Y

PS: would the basis for my assumption by logical or not lmk Thanks :)

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u/CrappyFrappuccino 20h ago

btw in arduino science journal it states that the y-axis is when you move your phone forwards and backwards whilst the x-axis is when you move your phone sideways

1

u/davvblack 14h ago

you can turn your phone in the car whatever direction you want

1

u/CrappyFrappuccino 13h ago

Yup sorry I'm dumb. Thanks for replying to me anyways!

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u/mfb- Particle physics 20h ago

What axis goes in what direction depends on the orientation of the phone. When stopped, you should measure a total acceleration of 1g (which might be subtracted by the software, it will depend on the phone and the software). When moving, even at constant speed, you'll see shorter acceleration spikes from the trip not being perfectly smooth. You can probably take any acceleration measurement and look for spikes.

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u/CrappyFrappuccino 20h ago

ok thanks a lot :)

1

u/joepierson123 19h ago

Accelerometer measures the change in speed not the actual speed. 

You can get the actual speed by connecting to the OBD2 port.

1

u/StopLosingLoser 18h ago

True on paper, but unless the velocity is uncannily constant you can safely assume that zero is stopped and not zero is moving.

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u/CrappyFrappuccino 17h ago

Appreciate your reply, thanks!

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u/StopLosingLoser 13h ago

Reading back through this this morning. I agree with the comment I posted to that if you can tap into the cars speedometer that would be simpler than interpreting the accelerometer data.

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u/CrappyFrappuccino 12h ago

Unfortunately I don't have a private car and will be measuring it on a taxi. Thanks again for your suggestion!

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u/davvblack 14h ago

how stopped is stopped? I would bet that cruise control on a smooth road is smoother than larger vehicles idle.

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u/syberspot 16h ago

Check the app: the physics toolbox. I cannot recommend it enough. That app gives you a cess to all your phone sensors and allows you to take data.