On Wednesday 01 March 2017 22:31:31 Jon Elson wrote: > On 03/01/2017 12:43 PM, Peter C. Wallace wrote: > > On Wed, 1 Mar 2017, Kirk Wallace wrote: > >> Date: Wed, 1 Mar 2017 09:55:49 -0800 > >> From: Kirk Wallace <kwall...@wallacecompany.com> > >> Reply-To: "Enhanced Machine Controller (EMC)" > >> <emc-users@lists.sourceforge.net> > >> To: emc-users@lists.sourceforge.net > >> Subject: Re: [Emc-users] MPG detents > >> > >> On 03/01/2017 04:42 AM, Roland Jollivet wrote: > >>> I had always assumed that machine MPG's generated one state change > >>> per click, but following Gene's discussion, I pulled out my 1988 > >>> Fanuc MPG, and saw that it was also 4-states per click. Obviously, > >>> one 'pulse'/detent > >>> > >>> Does anyone know the rationale behind this? > >> > >> I don't know, but in my opinion ... > >> there are four pulses per quadrature cycle and the pulses have to > >> follow a proper sequence for forward and reverse rotation. This can > >> produce a more reliable input for each detent location because a > >> proper set of pulses are needed. If there is any electrical or > >> mechanical noise (detent close to a pulse, machine vibration) and > >> we use only valid cycles, rather than raw pulses, we will have a > >> more robust input. It is sort of like using parity checking on data > >> words and maybe hysteresis (more than one pulse to change a state > >> either way). > >> > >> > >> -- > >> Kirk Wallace > >> http://www.wallacecompany.com/machine_shop/ > >> http://www.wallacecompany.com/E45/ > > > > I agree, I think the optimum is to use a 100 PPR MPG with 1X > > quadrature mode (so 100 counts per rev) with the count occuring 1/2 > > way between detents > > > > This means > > > > 1. You can move a known distance by feel > > > > 2. The MPG will not jitter back and forth with minor vibration/ hand > > motion since it needs to move all the way to the "hump" between > > detents to count > > I use a 100 "pulse" MPG, and the encoder counter counts all > transitions, and have no problem with jitter, and can count > off the detent clicks by feel. There isn't much jitter on a > 100 pulse/rev encoder, especially with the detent. > I also have a button that has to be held to enable jogging, > so there will be no jitter (or movement at all) when that > button is not being pressed. That saves me from accidents > when I bump the MPG dial. > > Jon > That is a concern here too, but would need another run of cat5 jumper cable to do. I may, in the halfile, put an activity timeout of say 5 seconds of allowable activity after the range switch was toggled off, and I am leaning toward ditching the pushbutton for a spring loaded to off toggle/bat handle type.
Its my understanding that if motion is running gcode, that the jog inputs are disabled? But I still think the timeout is safer. Using a separate switch takes a wire I don't have in a piece of cat5. I can put both dials and an enable speed jog in one cable as it is. Too many SS pipes across the saddle though, so I may bite the bullet and put in another piece of cable-chain from the middle of the beds bottom up to the apron to get all this onto the apron. That too is a fugly thought... But I have it available and its not doing anything but laying on the bench now. But I'll probably hold it in position for ten seconds and go get another piece of the SS pipe & make new clamps to hold it. And the clamps are 2-3 hours fiddly to make as I am out of the right sized scrap alu and will have to cut them out of a bigger block. And today is shot already on this side of the pond. Sigh. Cheers all, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
