I'd consider buying a real encoder off Ebay or similar. With a decent encoder, and the software properly setup, threading works exactly as expected. Just make sure that you don't get an encoder with too many Pulses per rev if you are strictly using a LPT port to read the encoder.
I purchased an encoder off Ebay (about $60) and then bought a couple of chips to translate the differential encoder signal into a lpt compatable signal. (about $20 for the adapter) It works very well. So well that I am going to add a Mesa card so I can use the encoder at full spindle speed, for feed per rev, and constant surface speed instead of just threading at lower speeds. Dave On 4/23/2010 12:12 PM, Schooner wrote: > Hi > > My first time here, hope you can assist. > > I have a working stepper driven lathe under Mach, but am not happy with > Mach on many levels and use Linux for everything else, so am migrating > to EMC2. > > I have all the basic stuff working, but I cannot do any threading. > > I have a single pulse from the spindle from a hall-effect sensor. > > (On the opposite side of the pulley I have embedded 4 magnets, 1 x 10mm > and 3 x 4mm, which if the pickup is shifted, give a 'timing pulse' which > works with Mach, so could use that set up) > > I found an archived reply on this forum as below to a very similar query > > /"You need an index input, as EMC doesn't start a threading pass until > it sees an index. > Looking at http://www.linuxcnc.org/docview/html/examples_spindle.html > (the last section) I think you need at least the following lines added > to your HAL > > > loadrt encoder num_chan=1 > addf encoder.update-counters base-thread > addf encoder.capture-position servo-thread > setp encoder.0.position-scale 1 > net spindle-position encoder.0.position-interpolated => motion.spindle-revs > net spindle-velocity encoder.0.velocity => motion.spindle-speed-in > net spindle-index-enable encoder.0.index-enable<=> > motion.spindle-index-enable > net spindle-pulse-and-index parport.0.pin-11-in => encoder.0.phase-A > encoder.0.phase-Z ;set to correct pin. " > > /I am afraid I do not understand how encoder.0.phase-Z could be > connected to anything, there is only one index pulse. > > I included the above into my .hal minus the last line. > The lathe still does not start a threading cycle and if I watch the > spindle-pulse-and-index, it does change but only every 5 seconds or so, > not continuous flickering as I would expect. > > If I rotate the spindle manually, I get a positive indication every rev, > so maybe the hal monitor > display just cannot update quickly enough. > > Have I missed something or is the answer that you cannot thread with > just an index pulse and you must have a timing pulse too, connected to > encoder.0.phase.Z perhaps?? > > Would my 4 magnet set-up through a second pickup provide that, if a > timing pulse is required , or is that too coarse? > > thanks > > Mick > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
