On Monday 06 August 2007, Roland Jollivet wrote: >(second send,..) > > >Hi list > >Concept query; >Looking at stepper drives, the general format seems to be 4 phases out, or > Dir+Step, obviously saving two I/O lines. > >So why isn't a two phase signal used?. A 'quadrature' output? >- you still use two lines >- less worry about pulse duration >- transmission line speed requirement is slightly eased as the lines step > alternately - it applies equally to stepper or DC servo drives >- there is no(or less) problem of timing error on direction reversal since > the signal changes are 'slow' at this point > >Maybe this is common, or what did I miss? > >Regards >Roland Jollivet > 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. > >------------------------------------------------------------------------- >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 -- 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) One can search the brain with a microscope and not find the mind, and can search the stars with a telescope and not find God. -- J. Gustav White ------------------------------------------------------------------------- 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
