At 02:37 PM 1/7/98 -0600, Norm Cramer wrote:
>Thought of this but I need to know the position of the pot.  It needs to
>physically stop at the high limit and physically stop at the low limit.  I
>couldn't find any encoders that would do this and give me 128 steps.
>
>At 11:25 AM 1/7/98 -0600, you wrote:
>>maybe you should look at an encoder. they require two inputs but are
>>digital.
>>www.digikey.com lists them starting at about $2.50USD.

Here's an off-the-wall idea:

Use an encoder, such as the Digi-key #3315Y-1-006-ND, which gives 6 pulses
per revolution on each of the two outputs.  Thus, each revolution gives 24
detectable states.  Use two gears, one on the shaft of your knob, and one
on the shaft of the encoder, to multiply this 24 out as far as you need it.
 A six-to-one ratio will give you 144 states per revolution, which will
allow you to have 128 states with only eight ninths of one knob revolution.
 Physical stops at each end of the range can be achieved by adding a pin
sticking out of the knob's shaft or the side of the gear, and two
appropriately placed stops for it to bang up against.

What is the requirement that the end stops be physical?  Appropriate visual
or audible feedback of the current setting might be simple to achieve, even
with an encoder that requires multiple turns to cover the full range of
settings, and might make an appropriate substitute for "physical" feedback
(e.g.: end stops).

Hope these ideas help you think in directions that help you solve your
problem!

 - Rick

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