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 ------------------------------------------------------------------------------ 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
