> "And wasn't the whole point of a rotary encoder the fact that it
> didn't HAVE a 'home' position?"

Yep, you are correct.  The discussion sort of morphed into this.

Here's another idea -- use an R/C servo, and mount the knob on it
free-floating.  That way, turning the knob does not turn the
servo.  Now mount 2 microswitches on the servo arm with the knob
hitting (and stopping on) the microswitches turned cw or ccw.
Now, move the servo accordingly with code.

Only problem is "feel".  The micro switches would need to be
small "pots" with springs to indicate how much pressure is being
put on the knob, so it can rotate at a variable speed based on
how fast the user is trying to move it.

Ah yes, Rube Goldberg is my hero!

Cheers,
-Neil.



-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Robert Rolf
Sent: Friday, June 28, 2002 11:16 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: stepper "digital" knob viability


The Sony control has a normal stacked pot with a tiny DC servo motor hanging
off the end. You can probably get it as a replacement part, but it won't be
cheap. There are probably other consumer systems with this kind of pot in
it.

And wasn't the whole point of a rotary encoder the fact that it didn't HAVE
a 'home' position? If you want a powered control, why not use an R/C servo
with a low gear ratio so it can be 'back driven' or with a friction clutch
and continous motion (like the modified Paralax robot servo).

And if you used a PIC with comparator inputs (16F87xA series) you'd only
need 4 pins since you could tri-state the drive pins when you're not
driving the motor. Just be sure to have zener clamps on the motor coils
so that it's 'childproof'.

R

Pic Dude wrote:
>
> My all-in-one Sony mini component system does that (it's
> about 14 years old).  I don't think it's a rotary encoder
> cause it has a definite start and end, and has no detents
> (very smooth).  But altering the volume on the remote will
> change the physical position of the rotary knob.  Has a
> cool little LED on it too, to indicate the setting/position.
>
> Cheers,
> -Neil.
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Ammerman
> Sent: Friday, June 28, 2002 7:06 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: stepper "digital" knob viability
>
> >And what would be really cool using a stepper motor is when you power up
> the project, the control 'moves' back to the last >stored position nice
and
> smooth...
>
> Or when  you use the infrared remote, the control tracks the action of the
> remote.

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