31 Oct
2002
31 Oct
'02
12:38 a.m.
Actually, that system worked very well. The same
technology was used in Diablo Hytype II printwheel and
carriage motors.
I once repaired these, and their Qume clones; The
Qumes had optical encoders that would get dirty, fail
and were very difficult to clean without breaking the
encoder glass. The Diablo's would work fine in very
dirty environments.
--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
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So you want to
build a contrabass? I have never
heard one...
but I have always been skeptical about its
ability
to put out HiFi.
The reason is that people use DC servomotors with
*brushes*, and
believe, the behavior of these things at low
speeds is very nasty
in terms of nonlinearity: static friction,
nonlinear torque(i,theta);
It never fails to amaze me that the head positioner
in a Diablo Model 30
hard drive (aka DEC RK02, RK03) is a
permanent-magnet DC motor with
brushes. It drives the heads via a rack and pinion
mechanism. On top of
the motor spindle is a pair of PCBs that form a
'transformer' which
provide the Sin and Cos signals for the servo (like
the optical
transducer in an RK05).
Somehow they got this servo to work...
-tony