AVR-Chat

--- In AVR-Chat@yahoogroups.com, David VanHorn <dvanhorn@c...> wrote:
> At 08:05 PM 6/28/2004 +0000, Phil wrote:
> 
> >Some one did do just that.  check out this page - 
> ><http://www.portlandrobotics.org/robots/servo_encoder/index.html>
> >
> >but wouldn't an optical encoder simply tell you relative motion 
(not 
> >absolute)?  
> 
> Depends on the encoder. Gray code or binary units give absolute, 
quadrature gives relative.
> 
> >How important is it to know the initial position?  You can command 
a 
> >servo to a known position and go from there.  
> 
> Good point.

depending on the thing, it could be a problem.  A car or buggy is no 
problem, but robot of some sort could need to start where it left off 
and a re-zeroing could present a problem.

Encoders in the simplest form are disks with holes.  the can reveal 
direction.  The larger quantity of holes will offer higher resolution 
and typically encoders are used for speed and/or direction.

A Gray scale (for Frank Gray the first patent holder) encoder is not 
only incremental (direction, speed) but it is also Absolute.

With a Gray Scale encoder, you can know the exact posistion of the 
wheel.

Of course, the greater resolution means the higher number of sensor 
lights and patterns on the wheel.

a colored wheel could show relative posistion as could a pot.


Dave