From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: steppermotor as encoder -> presto, moterized pot.
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
Date: Tue, 08 Oct 2002 03:02:38 GMT
NNTP-Posting-Date: Mon, 07 Oct 2002 20:02:38 PDT
Richard Steven Walz wrote:
> 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??
Do they still make them? I haven't seen any in years. As I remember,
their position is unambiguous because the stator is three phase with six
pole shoes and the rotor has two poles. This is going back into ancient
history - carrier control.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org