Detecting Horizontal Movement

[Atom058]

Darrel - Thanks for your response, but don't accelerometers just detect changes in speed? I would think that once speed was constant, there would be no signal until the speed changed again (sped up or slowed down). Jeff

[rsocor01]

Darrel - Thanks for your response, but don't accelerometers just detect changes in speed? I would think that once speed was constant, there would be no signal until the speed changed again (sped up or slowed down). Jeff

Yes, you are right. The acceleration of any object is defined as dv/dt, which is a change in velocity divided by a given amount of time. If the velocity doesn't change then the acceleration is zero. However, if you want to detect your own movement, running or walking, chances are that you won't be able to maintain a constant speed. There would be small fluctuations in your body speed that the accelerometer would be able to detect.

Robert

[Ioannis]

May be a gps module can help if the speed is over its lower detecting limit.

Ioannis

[mackrackit]

Add a compass and you have everything a "smartphone " has. They work very well for tracking movement.

[Ioannis]

But Dave, if you are moving to the direction the compass is showng, then I suspect no movement will be detected.

I have not used a compass, so this may not be true.

Ioannis

[mackrackit]

I have not used a compass chip but the coding I have done with Android shows the compass to be very sensitive. I can not move in a straight line without averaging. It would be interesting to see what a raw chip does.

[Atom058]

Thanks Guys - Price is a factor (of course), so GPS will probably be out. Rsocor01, you have a point about the "jarring" effect of walking and the use of an accelerometer to detect that, but now we are getting back to vibration... Not sure how reliable that will be - might still be an option. My dream sensor is something that could be aimed at the ground and can determine when what it is looking at has changed - as what happens when an optical mouse moves. If I could hold an optical mouse 3 feet off the surface and still have it detect movement, that would be ideal, but we all know that won't work...

[Acetronics2]

Hi,

Bo need to put your head under the sand ...

a location device will be necessary : moving at a constant speed doesn't produce any accelaration and compasses changes are too weak to be seen.

so:

1) a string fixed to a reference point ( the simplest ... )
2) a surveyor dog
3) a wheel on the ground
4) the RSSI indicator of a Rx chip ( need a Tx somewhere in a reference point ...)
5) a stupid GPS device ???

you already have locating devices on the market ( for dogs, old persons, cars ....) so, try to see how they work ...

Alain