# Help choosing sensor for project

Hi guys,

This is my first time posting here so idk much about rules and the usual structure of this kind of posts, but anyway.
I'm planning on doing a project that involves meassuring the speed of an object that falls through a tube (which is filled with a liquid) and i have two major issues:

1. I can't think of a proper sensor to meassure the speed since the object is actually inside the tube and in the water and therefore i guess the usual proximity sensor would just detect the glass and not the object itself.

2. I only need the constant velocity, considering that the object will accelerate during the fall until it reaches it's maximum velocity, therefore it's the maximum velocity that i'm looking for.

Any ideas on how to do this using arduino UNO?

leonel_robledo:
Hi guys,

This is my first time posting here so idk much about rules and the usual structure of this kind of posts, but anyway.
I'm planning on doing a project that involves meassuring the speed of an object that falls through a tube (which is filled with a liquid) and i have two major issues:

1. I can't think of a proper sensor to meassure the speed since the object is actually inside the tube and in the water and therefore i guess the usual proximity sensor would just detect the glass and not the object itself.

2. I only need the constant velocity, considering that the object will accelerate during the fall until it reaches it's maximum velocity, therefore it's the maximum velocity that i'm looking for.

Any ideas on how to do this using arduino UNO?

You don't want to "measure" the speed. You want to know the time it takes to pass two points, then you compute the speed. Since you seem confused in #2 as to what speed you want, and you will never get a
"constant velocity", I guess you want to terminal velocity.

I see the tube is glass. Is it transparent? Is it round or some other shape? can you shine a light through the glass and water? Can you use a light detector the see the light? Then can you obscure the light with the object? If so, you can use two light sources and two detectors a measured distance apart and connect the Arduino to the light sensors and program it to determine the time for your object to pass from one detector to the other. From that time, you can compute the speed.

Paul

Most proximity sensors are pretty good at sensing metal and poor at glass and plastic. If there's a gram or two of iron in the falling object, it will be easy to detect from outside the glass.

Paul_KD7HB:
You don't want to "measure" the speed. You want to know the time it takes to pass two points, then you compute the speed. Since you seem confused in #2 as to what speed you want, and you will never get a
"constant velocity", I guess you want to terminal velocity.

I see the tube is glass. Is it transparent? Is it round or some other shape? can you shine a light through the glass and water? Can you use a light detector the see the light? Then can you obscure the light with the object? If so, you can use two light sources and two detectors a measured distance apart and connect the Arduino to the light sensors and program it to determine the time for your object to pass from one detector to the other. From that time, you can compute the speed.

Paul

Yeah i was thinking of a photoresistor and a led, but i'm uncertain of how good the measurement will be. Do you know what information the ArduCam provides? I was told by a friend that i could use that, but i don't know if that cam can detect objects or whatever data it provides.