> From: John Craddock Step and Direction Input Servo Drive John I have done just this. I have done a digital timediscreate differential servo, which uses PC as a track control for 1-8 axis. The digital servo only looks step/dir pulses from PC and makes positioning using a feedback from pulse counter(A/B max 12 MHz). NC program reads standard NC files (RS-274D). A PC is slow, DOS based 486 66 MHz. Still it can drive 44kHz steps for 3 axis. Each servo has one PIC16F873 12MHz + digtial pulse counter (=AMD MACH4-64 PLD). A cpu has three PID potentiometrs to adjust servo parameters. A serial debugging port(RS-232 56kbaud) serve also as position indicator. A PWM (10bit) /DIR signals goes to digital servoamplifier L6203 (40V 4A) Digital servo is made for my autorobot in horce races. See http://www.saunalahti.fi/pri/autorobot.htm. The motor controls the carburator with a metal wire. A start car accellerates horses automatically first 363 metes according the specifications for each start. A printed document is included for records. Second application is a plasmacutter for my friend friend in Robotics Accociation. I have prepared a presentation (Servo Control Secrets) for our next robotics meeting. Anyone want to come and hear it? -- See also a link below which show a part of SMD-placer head, which has also a digital servos. This is only testing a new servo pricnple. http://www.psavolainen.net/robotics/tampere2003.htm My Homepage is http://www.kolumbus.fi/probyte Pekka -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body