AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Richard" <richardt.bradshaw@...> wrote:
>
> Hi everybody I have been hanging around here for a while, great forum.
> Do any of you have any experience with accelerometers? I am thinking of 
> a project using an accelerometer to measure angles. The idea is this: 
> the accelerometer will be on the outer edge of a wheel. As the wheel is 
> turned the position of the accelerometer will move then using a bit of 
> grigonometry I can calculate the angle that it has moved through. My 
> question is how much accuracy can I get. I will be looking to measure 
> fractions of a degree on the wheel aprox 4 inches or 100mm in diameter. 
> Doing the maths gives a movement of about .88mm/degree so I would like 
> to be able to detect movement of about 0.2mm is this realistic?
> Cheers Rich
>

Accelerometers are typically dynamic "sensing devices".  They sense
"change" and are not a good choice for your electronic protractor
device.  A cheap way to go is to use a resistive potentiometer ( a
simple POT ) with a weighted pendulum.  A more sophisticated method of
measuring the tilt angle you desire is to use an optical encoder who's
shaft has a pendulum with a mass at the end. You could get "uber"
fancy with gyroscopes and such, if you wanted to make a real science
project out of it.

M5