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> <3DA3B2F4.F6F7D0BC@webaccess.net> <email@example.com>
Date: Wed, 09 Oct 2002 11:47:52 GMT
NNTP-Posting-Date: Wed, 09 Oct 2002 04:47:52 PDT
Richard Steven Walz wrote:
> In article <3DA3B2F4.F6F7D0BC@webaccess.net>,
> Chuck Simmons wrote:
> >Richard Steven Walz wrote:
> >> In article ,
> >> Tony (remove \"_\" from email address) wrote:
> >> >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).
> >> >
> >> >Tony
> >> ----------------
> >> That's true, selsyns are one way, I recalled after I reviewed my notes.
> >> It may be possible to sense feedback on each coil and arbitrate it into
> >> rotation data, however.
> >> -Steve
> >No. If you connect them together and apply power, when you turn one the
> >other turns the same. The motion of one will be repeated at the other.
> >Thus you can sense the windings to determine position or you can drive
> >to a position. The torque, even from large selsyns is not great. If I
> >remember correctly, they work as followers with three phase power on the
> >stators or single phase on the rotors.
> The ones I have doc on are the ones used on battleships, they use an
> amplifier from tiny ones to great big ones.
The specifications might not mention yje fact that selsyns will follow
each other. They were normally used in carrier control systems to
produce a rotational error signal that was amplified and used to drive
an AC torque motor. The use of an AC error sensor makes it unnecessary
to convert a DC error to an AC error. I suppose on battleships, the
selsyns might be used in gun mount controls and the like. I know that
they were used in the B-29 fire control system in WWII. AC carrier
control is less common than it once was because with modern components a
DC error is more convenient.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org