On Mon, 07 Nov 2005 18:38:33 GMT, "CWatters"
wrote:


"CWatters" wrote in message
...

"Eric Meurville" wrote in message
...
It would be great if the position sensor output could toggle every
360/2^N°, with e.g. N=6 (that means every 5.625°). More would be better.

If the rotor is a two pole magnet, perhaps you could surround the rotor
with
say 64 hall effect sensors. Scan and convert the analog value of each
sensor
many times a second and "plot" a graph. Do averaging to improve S/N ratio
and curve fitting to look for the maximium and minimium flux positions
(indicating where the north and south poles are).

However I think I would investigate using something else in the rotor -
perhaps a directional antenna/coil that's externally excited? It's usually
better to start with an AC signal rather than a DC signal if you think you
are going to have S/N ratio problems.

I forgot to add...

You will need to deal with noise produced by whatever is spinning the rotor.
Hope you don't have an electric motor too close to it.

---
LOL, go back and read the thread. It's _part_ of an electric
motor!


--
John Fields
Professional Circuit Designer