Detecting Horizontal Movement

[Atom058]

Darrel - Thanks for that very nice example! I completely understand what you are trying to get across now. One last question... will this be sensitive enough to tell if you slooowwwwllllly coast to a stop?

Thank you to all of you who replied to this post! I hope everyone has a safe and happy New Year! Jeff

[Atom058]

Just did a quick look at Sparkfun for accelerometers and found that they have a bunch that look like they could easily be used with PICS. They have a nice comparison here:

http://www.sparkfun.com/tutorials/167

FYI - Jeff

[Darrel Taylor]

That depends on how slowly you coast, the resolution of the sensor, maximum speed and other factors.

You never really gave us an idea of what you are doing, other than moving over different surfaces, so I can't say.

[Atom058]

Darrel - Unfortunately, you just about know as much as I do. The person that wants me to do this is being pretty secretive. Here is a little more... I am assuming it is a motorized vehicle and the position of the wheels will not always be the same, so they can't be used for indication. This will be in an outside environment, moving over any type of surface from very smooth to rough (grass, dirt, pavement, snow, etc.) at a pace that can range from 1/2 normal walking speed and up. Ideally, they are looking for something that they can just aim at the ground and determine that it is moving. They are not concerned about speed or direction, just movement. Height of sensor can be about 3 feet. Oh yeah, and cheap (duh) ... I am leaning towards a vibration sensor, but I don't know enough about the end system to be able to say that it would be 100% reliable - I have not tossed out the accelerometer, thanks to you... So there you have it... And again, thank you for your input. It is appreciated! Jeff

[mackrackit]

At first I thought this was a "person carry" project.

I wish to detect my movement over ground

Mounting to a vehicle has more possibilities.
These a very nice units.
http://www.dickey-john.com/product/radar-ii/

[Ioannis]

Wow, nice sensor! And heavy too, over 2kg !

Darrel, i was thinking about the integration of accelerometer and humbly appologize for my doubts. The spikes in the oscilloscope snapshot clicked me.

Ioannis

[rsocor01]

Darrel, i was thinking about the integration of accelerometer and humbly appologize for my doubts. The spikes in the oscilloscope snapshot clicked me.

Ioannis

Well, I had my doubts too, but not anymore after studying Darrel's program .

There are a couple of things that I wanted to mention. First, for this program to work properly it is assumed that the initial speed of the integration is zero. In other words, it is assumed that when the program is started the speed that we want to measure is zero. Second, referring to Alain's comment

Try this into an elevator ( or an automated train ) and I promise you will stay a moment in it calling for help ... !!!

Alain

You have a point there. So, it is necessary to obtain all the 3-axis acceleration components (X, Y, and Z) and calculate the resultant acceleration vector to obtain a valid result for the speed. There shouldn't be any problems with this program.

Robert

[Ioannis]

it is necessary to obtain all the 3-axis acceleration components (X, Y, and Z)

Darrel noted that too.

Ioannis