[ale] [Almost totally OT] Rotating hardware interface.

[Joe Knapka]

This is an unusually weird question, even for ALE. However, I assume
that the denizens of ALE can collectively answer nearly any
conceivable practical technical question...

I've got a gob of electronics mounted on a spinning rotor, which I
need to control via a PC parallel port. (Some small green gnomes awoke
me in the night and told me to do this; I don't ask questions.) The
ON-topic bit is that I'm using the parapin library
<http://parapin.sourceforge.net> under Linux to write the driver;
parapin is a very nice hunk of software.

The OFF-topic bit is that interfacing the parallel port to the
spinning gizmo presents a mechanical engineering problem that I'm
having trouble solving effectively, and I don't know where to begin
looking for the "right" answer. The angular velocity is on the order
of 300 RPMs. At the moment, for proof-of-concept, I've got the I/O
pins on the spinning thingy connected to some 22-gauge wires that just
crudely wrap around the motor shaft, and another jury-rigged set of
stationary brushes (also made from 22-gauge wire) that make annoyingly
intermittent contact with those loops, and to which the parallel port
is connected. It kinda works, but it's not very reliable, and the
crappy brush mechanism places a noticable mechanical load on the motor
(RPMs decline significantly when the brushes are in contact with the
loops, even though the motor power supply is completely isolated from
the power source driving the electronics).

I bet there's some standard solution to this kind of problem that I'm
just not aware of, which I could adapt to my needs. Any pointers
thereto would be greatly appreciated.

Thanks,

-- Joe Knapka

-- 
"Meet the new boss / Same as the old boss..." -- The Who
... Oh well, at least there's 2008.
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