From: "Tony (remove \"_\" from email address)"
Subject: Re: steppermotor as encoder -> presto, moterized pot.
Date: Wed, 09 Oct 2002 11:10:39 +1000
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
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For all the desirable attributes of Selsyns, then don't really address the issue
here- the OP wanted to use the knob as both input and output. You can simulate a
Selsyn waveform to drive one as an out device, OR you can sense the waveform and
use it as an input device, but to do both you need to do something similar to
what I suggested for the stepper solution (and even if you can still get
Selsyns, old floppy drive motors are still lots easier to get).
On 08 Oct 2002 02:16:34 GMT, email@example.com (Richard Steven Walz)
>In article <firstname.lastname@example.org>,
>Tony (remove \"_\" from email address) wrote:
>>On 06 Oct 2002 22:43:52 GMT, email@example.com (Richard Steven Walz)
>>>Okay, problem. When you turn a stepper VERY slowly, nothing comes out of
>>>it. You STILL need either a motorized pot or encoder or some sort on the
>>>stepper shaft. Now a geared stepper would probably work!
>>Yes, this is the real issue, but it can be overcome.
>>A disk drive stepper is ideal, its normal detent torque should be enough without
>>any holding current, and the position can be measured (even if the shaft is
>>turned infinitely slowly) by a differential inductance measurement, instead of
>>BEMF. Perhaps if the stepper coils are PWM current controlled, a tiny bit of
>>excitation will be enough to sense inductance. One of the AVR's timers could
>>drive the PWM, and also a CMOS switch to synchronously detect the inductance
>Why not just use some three-phase selsyns??