Roland Jollivet wrote: > > My question is; if one built a headless system(no video) and disabled > drivers wherever possible, would such a system be fast enough to run DC > servo's and read the encoders on the parallel port? > You have to figure this out for each case. What is the maximum encoder RPM at the desired rapid feed rate? (Don't forget belt reduction.) What is the base thread rate?
For example, 60 IPM, 1000 cycle/rev encoder and a 2:1 belt reduction to a 5 TPI ballscrew. So, that is 60 * 5 * 2 * 1000 * 4 (encoder quadrature) / 60 secs/min = 40,000 counts/second. Well, that is a bit iffy, a count every 25 us. And, remember that if the encoder exceeds the rate at which the computer can count the pulses, you get a servo runaway, which is a lot worse than just losing position with a stepper. Now, if 30 IPM is OK, and you have 250 cycle/rev encoders directly coupled to the 5TPI screws, it should work fine, but that is a lot of compromises to avoid a better interface. I generally think that running steppers via software step generation is not a great thing to do, and running servos via software encoder counting is far WORSE! So, now you are suggesting using TWO computers instead of using purpose-built hardware to interface to the motion system! Now, you have to have TWO hard drives to back up, and TWO computers to boot and shut down cleanly. There may be times such an arrangement is desirable, but I really think it is the wrong approach. Jon ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
