[chbot] Shaft Encoder

[Richard Jones]

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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