Gene Heskett wrote: > For steppers, its generally better to offload the actual stepping to the > motor > driver. Most motor drivers actually use a pwm sort of overall current > control, switching at 20 to 75 kilohertz a second. This also, by fiddling > with the currents within the driver, allows microstepping to be done, in > increments as fine as 1/10th step for some drivers. My own does 1/8th step > and its almost ghostlike to see the motor turning at about 1/2 of an rpm in > steps so small you have to look close to see its not a constant, essentially > silent motion. > > The best you can do with quadrature signals is full step, and to get any > torque at speed, you'll dump 98% of the motor power in current limiting > resistors, big ones that still need active cooling. 40 years ago maybe, > today? Makes no sense at all. Let the driver take care of the grunt stuff.
Roland is NOT suggesting that the 2-phase signals be used to directly drive the motors in full-step mode (at least I don't think he is). I believe he is wondering why more drives don't accept quadrature instead of step/dir as inputs. Either one can be used to tell a micro- stepping drive when to take a step. But quadrature has less critical timing requirements, is more noise resistant, and can control a higher step rate for a given wire (or optocoupler, etc) bandwidth. The only reason step/dir is more common than quadrature is inertia. As long as most drives only support step/dir, most controls will have to produce step/dir. Even if controls can also produce quadrature, there isn't much incentive for drive makers to switch over. Regards, John Kasunich ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
