Chris Radek wrote: > On Sat, Mar 28, 2009 at 11:39:07PM -0500, Jon Elson wrote: > >> Hi, all, >> >> I'm trying to put together a jog pendant to show at NAMES. To save >> digital I/O points I want to multiplex the axis selection, then I can >> select 3 axes with 2 points. But, I need to do a demultiplexer, like >> the reverse of the mux4 HAL component. I don't see such a component, so >> maybe I am missing a simple way to do this numerically, or something. >> Any ideas, or should I write a new component? >> > > I can imagine doing it with a sprinkling of and2 and not components, > or the logic component, or ladder especially if you are already > using ladder. > > No, I haven't learned Classic Ladder, yet. I suppose I should..... Ahh, I missed the Logic component, that might be just the thing. I'll have to study the docs and then fiddle with it to see exactly how the outputs work. Thanks! >> While I'm asking questions, is there an example anywhere where a spindle >> speed tach is set up to display on the VCP? I have a shaft encoder on >> the spindle of my minimill, and wired to an encoder counter on my UPC >> board, for threading operations. I can see that just taking encoder >> delta (raw encoder counts) from the PPMC driver and multiplying by the >> right factor would give RPM most of the time, but it would glitch when >> the encoder counter is syncing up for threading. I'd have to hard-code >> in the servo period, too. Also, a bit of filtering would give a more >> stable value. Has anyone done this? Are there better signals on a HAL >> pin somewhere? >> > > http://www.linuxcnc.org/docs/devel/html/hal_general_ref.html#sec:CanonEncoder > OK, well, I'm not sure what you use to scale a spindle encoder, to get the scaled velocity output. I see how a linear or rotary axis could be scaled to produce inches, mm or degrees per second. What would be the right scaling for a spindle, revs/second? The current PPMC driver doesn't produce scaled velocity, only raw (encoder count) delta since last sample. Sounds like something I should work on, maybe at the Fest!
> It's up to the driver to figure out how to make a good velocity > output. As you say, if the driver doesn't do this, you can use ddt or > a delta debug output, but it won't be index-safe. Seb put a lot of > effort into the velocity output of the new mesa drivers lately, and > they are index-safe. It would be nice if the ppmc encoders had this > feature too. > > OK, I'll have to look at this. I wasn't necessarily looking for this to be in the driver, but if that's where it is being handled, i guess I should go along. > I notice the hal doc doesn't specify that the velocity should be > index-safe. It goes on to mention the simplest implementation > which is NOT index-safe as described. John K, what was the intent? > > sim/lathe has a spindle speed readout you could copy. It's pretty > simple. > Thanks, I'll check it out! Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
