On Wednesday 19 October 2016 01:01:18 Danny Miller wrote: > A friend showed me this today, not powered up yet: > > https://www.kickstarter.com/projects/tropicallabs/mechaduino-powerful- >open-source-industrial-servo-m > > At first I was confused, it says it's a stepper, but with an encoder, > and lowers or disables drive current when not needed. Or you can > freewheel it and it'll maintain the coordinate system. It cannot > stall without the system knowing, and a stall won't corrupt the > coordinate system. > > But there's no mechanical connection to the motor, it's this new > AS5047D high speed, high resolution magnetic rotary position sensor: > > http://ams.com/eng/Products/Magnetic-Position-Sensors/Angle-Position-O >n-Axis/AS5047D > > You glue a magnet to the rear of the motor shaft, and keep the sensor > like 1/4" away. Note it not only counts delta, it knows absolute > rotor position. > > Gives 2000 counts/rev. That's enough that it could effectively show > rotor phase through a single fullstep, which would allow for more > stable electrical control of stepping. There's an initial calibration > phase that drives a phase so it knows where the TDC of Coil A is in > absolute position. > > They set it up so it powers down and freewheels, except it will hold > its position by powering coils when needed. It can also reduce > current to product only the torque needed to follow the step commands, > instead of always operating at full current. > > Well, my mind is blown! > > Danny > That does indeed sound very handy for stepper users. But the sensor magnet I do not envision as being on the motor, but on the ends of the screws driving the machine. That will give 16,383 discrete positions of the screw per revolution of the screw, irrespective of any stepdowns from belt drives etc between the motor and the screw. I did not see a price for the completed board and magnet, just for the AMS device. Ahh, did find it on the pre-order button, $47 a copy for version 0.1.
Did anyone else? If not too outrageous, I might be interested in a pair of them to put on this Sheldon conversion as a test bed. But I'll do the conventional way first & see where it falls over. What I would really like to see would be a light beam that a tool could be advanced into in order to both adjust the tool tip height, and set the tools zero radius offset. Something whose shadow could be detected by a 4 cell photodetector in the tailstock socket. Or even a low res cmos imager would suffice for the detector. Almost anything to get us into the +- .005" range for a first pass calibration cut. Comments? Gotchas? Cheers, 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
