[chbot] Shaft Encoder

[Synco Reynders]

Hi Richard,
Fridge Magnets. They are essentially N S N S... with about 4mm spacing. You 
can actually feel the corrogation when rubbing together with another fridge 
magnet. Then just cut into strips.
Hope this helps,
Synco

On Thursday 04 September 2008 08:34, Richard Jones wrote:
> Thanks Charles,
>
> The UGN3141 Hall effect sensor from South Island Components does look
> interesting, a little more expensive than optical.
>
> To ensure that the hall effect sensors get low enough gauss to release do
> magnets need to be alternated N S N S? That would mean an even number so to
> detect direction of rotation you need 90 degree separation between hall
> effect devices rather than 180 degree that works with an odd number. Where
> do you get your tiny magnets?
>
> I wonder if you might be able to place the hall effect sensor somewhere
> inside a brushed DC motor?
>
> Richard
>
> On Thu, 4 Sep 2008 07:38:10 +1200, "Charles Manning" <cdhmanning at gmail.com>
>
> wrote:
> > Hi Richard
> > There's an alternative that we are dabbling with using a Hall Effect
> > sensor
> > that is probably a lot easier to do than shaft encoders.
> > The Hall Effect sensor is just a 3-pin transistor like device that
>
> detects
>
> > a
> > magnetic field (eg. UGN3141 from South Island Components). The magnet can
> > be
> > one of those tiny 2.5mm Neodymium magnets embedded in a gear (Drill a
>
> hole
>
> > and glue it in). Since some of gears inside the gearbox rotate quite fast
> > you can get pretty good resolution.
> >
> > On Wed, Sep 3, 2008 at 10:06 PM, Richard Jones <rjtp at ihug.co.nz> wrote:
> >> I came across this shaft encoder arrangement for the Tamiya Twin-Motor
> >> Gearbox: http://www.noplabs.com/twinmotor/twinmotor.html
> >> This came via the HBRC mailing list. Andrew showed something along these
> >> lines at one of our robotics meetings several years back.
> >>
> >> Richard
> >>
> >>
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