Re: [CAD_CAM_EDM_DRO] RE:hand jive

Alan

I think a lot of it is that people want to have something they can
grab hold of to feel in control ,we "need" the feedback that buttons
just cant give and we are more at home with knobs and switches that
we can feel
deciding on electronic vs. real handweels can depend on the
size of the machine ,the biggest machine you can reach the ends of
all the axes at once is about the size of a B'port OTOH as
Randy pointed out some work is too small to go by feel alone

I built a handweel from a full hight 360k drive, the spindle shaft and
bearings became the encoder shaft and the flyweel became a detent
plate with 100 indexed holes around the circumfrence and a knob fixed
on top
the disk hub end got turned down to a thin encoder disk with 25 slots
the opto pairs and spring detent are mounted in an aluminum housing
that I built for it ,a dividing head or indexer comes in handy for all this
the hard part was lineing the optos up so that each detent position was
at a seperate clean encoder state

the opto outputs (A&B) are conditioned with Schmitt triggers (74hct245)
and for now I'm playing with it on the 4 button inputs of the joystick port
(the analog inputs are useless but you get 4 digital bits for free)

the software loop only needs to be fast enough to keep up with the
loose nut spinning the weel ;-)
the speed limits are ,how fast can the axis catch up and the human
reaction time (slow in computer time)
most of the time you will be turning the handweel slowly enough for
the machine axis to catch up ,any faster and you will want the
jog state to reset for the next loop (the axis will still be moving)
and check for a state transition (keep moving Y/N?) you may
get one or two clicks more/less than you wanted at low jog increments
(.0001) if you could spin the weel as fast as your arm can move
and still keep count
its not all that important that the knob stay synced with the machine
position ,if anything you want the machine to fall behind of you spin
it to fast

Brian

On Sun, 05 Nov 2000, you wrote:
> Brian,
>
> Thanks for the comments. Expensive RF test equipment usually have knobs
> to spin. They may be shaft encoders, but manufactures have found that
> users want knobs, not just simple buttons. I think I'm seeing that it
> must be similar in the CNC control world.
>
> Well, you have track 0 sensor, cyl 0 sensor, spindle motor and a track
> stepper. And a "disk inserted" sensor. Not a lot more that I can
> remember off hand. Some of the early 8" disk drives had hard sectored
> disks, but I don't see much help there. What's your suggestion?
>
> I have 256 count panel shaft encoders (HP QEDS 7000) hooked up as A & B
> quadrature. A little hardware would help here! Looks like a fast loop
> is needed to watch for A & B changes, and ESC out of jog.
>
> Alan