Re: Rotary encoder


John Fields wrote:
> On Mon, 19 Dec 2005 22:20:57 GMT, no-one@xxxxxxxxxxxxxxxx (Robert
> Scott) wrote:
>
> >On 19 Dec 2005 12:07:30 -0800, "Pete" <designelect@xxxxxxx> wrote:
> >
> >>Hi,
> >>
> >>I need to make a rotary encoder which fits onto a motor shaft from
> >>which I will read the amount of movement in both directions.
> >>
> >>The way I want to do this is by using a mechanism similar to that found
> >>in a ball mouse where a slotted wheel interrupts the light to a pair of
> >>sensors.
> >>
> >>I've taken apart a couple of mice but can't find any markings on these
> >>devices (phototransistors). If anyone could point me in the right
> >>direction for a manufacturer, I would be very grateful.
> >
> >Before you re-invent the rotary encoder, look around for an
> >off-the-shelf solution. There are many many forms of rotary encoder
> >packages. They come in a wide range of resolutions. Most of them
> >have their own shaft which you would have to couple to your motor
> >shaft. However there are also the "hollow shaft" type that can be
> >fitted onto an existing shaft. In searching, use the term
> >"incremental encoder".
>
> ---
> Unfortunately, an incremental encoder won't supply him with the
> directional information he needs, so his search term needs to be
> "absolute encoder", and he'll also need to specify the resolution he
> requires.

The HP incremental encoders - HEDS-9100 and up - in the Farnell
catalogue all come with either two or three channels - the two channels
are two incremental outputs in quadrature, from which any competent
enigneer can get directional information, and the third channel - when
provided - is an index output.

In fact most of the incremental encoders in the Farnell catalogue
explicitly offer quadrature outputs, and I suspect the rest do too,
even if Farnell's copy-writers haven't bothered to mention it

Perhaps you might like to reprogram the relevant bit of your brain? You
seem to have posted one of those bits of information "that ain't so".

-----------------
Bill Sloman, Nijmegen

.

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