Re: [CAD_CAM_EDM_DRO] RE:hand jive

most but not all of the machines I've worked with have both
the jog buttons can be used in combination with the feed override
for large moves where acuracy is not as important while the
the handweels are both graduated and have magnetic or spring
detents and work with the jog increment settings to give a feel
of the work (most of the feel is actualy in your eyes and ears)
and let you do exact moves without having to look at the display
for example set jog to .0001 to touch off an edge finder then to .1 to
move to the real part edge with one click of the handweel
they also let you adjust the cutting speed without having to stop
,when you hear the tool start to complain just crank it slower

the comercial ones ARE expensive but its not all that hard to make
one yourself (hint:all the parts for one are in a 360k floppy drive)
the jog handweel may seem like a luxury item at first but once you
start using it you will have a hard time working without one

interfacing the encoder is where it gets tricky
the hardware interface can be just two pins on the lpt port like
you have already done
?was it wired in as phase A&B or step&direction?
the software needs to poll the bits once each time thru the
jog loop and command a move only on a change of state
if it only polls while in jog mode it shouldnt cause much of a
slowdown ,it should be less of a drain than the mouse is anyway

if you just stuff pulses into a fifo buffer like a keyboard does you
can have an axis run away from you if you spin the weel to fast ie,
if the jog increment is set at .1 then one casual spin of the knob can
cause big trouble (krunch!)
commercial machines dont let this happen ,they stop when the handweel
stops no matter how many pulses came in

Brian

On Sat, 04 Nov 2000, you wrote:
> Brian and the list,
>
> The Pulse generators look interesting (but expensive)! Would there be
> an advantage to having a shaft encoder to spin rather then a pair of jog
> buttons? Would the shaft encoder just provide pulses, or would it be
> "calibrated" like a real hand wheel? What do the big machines with this
> (electronic handwheels) do?
>
> I interfaced a shaft encoder through a spare pair of bits in a parallel
> interface to my RDF (Radio Direction Finder) hardware (Stepper spins
> antenna, A/D sync'd with antenna direction takes signal strength data).
> I didn't have all that smooth a motion, probably due to overhead of
> reading the encoder. I want to try it again with something like US
> Digital encoder interfaces (like DRO). I guess one could interface the
> encoder and simulate keyboard codes? Or if you're writing your own
> program... Any thoughts writers?
>
> Alan