On Monday, August 30, 2010 09:50:36 am Kent A. Reed did opine: > On 8/30/2010, Gene wrote > > >> > Guys, would you recommend some inexpensive encoder type hand > >> > controls? I would like to control "speed override" with a rugged > >> > encoder type rotary control. > > > > A thought that I have played with in my mind, and gone as far as to > > order a few parts, is to use a more or less std small stepper motor > > with 12 or 24 volt rated coils, as an encoder by feeding it to a pair > > of comparators which should give a quadrature A& B output. I > > haven't worked out a 100% reliable method of protecting the > > comparator inputs from the over-voltage a fast spin of the knob on > > the motor shaft would feed them, nor have I worked out the most > > reliable hysteresis feedback to prevent low level vibrations and such > > from outputting spurious signals. But, based on the fact that the > > average $3 stepper motor is also a heck of a good generator, I see no > > reason why it couldn't be done. > > Gene: > > I had what seemed a brilliant "aha" several years ago while idly > spinning a stepper motor in my hands and feeling the detent-like > resistance. Gee, it could almost be an electromagnetic encoder, I > thought. My sense of discovery dimmed when I went Googling and > discovered that only about a gazillion others had got there before me > :-(
I know that feeling well. > Still, the advantage of being a johnny-come-lately is that I could > profit from the experiences of others. I particularly liked the notion I > came across of biasing a motor winding to improve the signal-to-noise > ratio. I doubt I would have come up with that by myself. > > See, for example, > http://www.piclist.com/techref/io/sensor/pos/enc/stepper_as_encoder.htm That is ingenius. My thoughts were more along the lines of the schmidt trigger's deadband, but this would obviously work at reasonable rotation speeds too. Basically, anything to get away from the noise at rest by biasing the comparator one way or the other would suffice to kill the thermal noise. Its the creeping along, one bump at a time where I believe the schmidt trigger may be the better solution. Or maybe its the NIH syndrome? The motors I have output several hundred millivolts at one bump at a time speeds. > Regards, > Kent > > PS - I got bogged down in family health crises and never got around to > testing the approach and posting the results, at least not yet. Maybe > someday. > > ------------------------------------------------------------------------ > ------ Sell apps to millions through the Intel(R) Atom(Tm) Developer > Program Be part of this innovative community and reach millions of > netbook users worldwide. Take advantage of special opportunities to > increase revenue and speed time-to-market. Join now, and jumpstart your > future. > http://p.sf.net/sfu/intel-atom-d2d > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Once is happenstance, Twice is coincidence, Three times is enemy action. -- Auric Goldfinger ------------------------------------------------------------------------------ Sell apps to millions through the Intel(R) Atom(Tm) Developer Program Be part of this innovative community and reach millions of netbook users worldwide. Take advantage of special opportunities to increase revenue and speed time-to-market. Join now, and jumpstart your future. http://p.sf.net/sfu/intel-atom-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
