David Braley wrote: > Hello all, > > I wanted to say thanks again for all your input and help bringing me up > to speed! > > I'm cranking away researching my Anilam 1100 retrofit, and I'm having > troubles feeling secure about the parallel port as a robust enough > device to control three or four axis of motion at modest 100ipm table > speeds. I can see a PCI based I/O card doing it, but I'm feeling iffy > about the parallel port. I know that EMC is super competent using either > style device for it's main motion control I/O. > If you are using software-generated steps, then everything depends on the maximum step rate you need. If you need 50 KHz step pulses on 8 axes, you may have a problem.
I have a controller board that can be set up to generate step pulses for step/direction drives or PWM pulses fro servo drives. Using a 600 MHz Pentium CPU and the on-motherboard parallel port, I can control 8 axes worth of these controllers at a 2 KHz servo update rate. (The step output can exceed 300 KHz on all axes simultaneously, as the computer only sends velocity to the controller, not the individual steps.) With a PCI parallel port card, you can go to 5 KHz servo update rate. If you want specifics, with the UPC servo controller, the CPU reads 14 bytes for position and digital input status, and sends 10 bytes for velocity and digital output. Each byte transferred takes about 800 ns with an on-mobo port, and about 600 ns with a PCI port card. The whole servo update cycle takes about 100 us for 4 axes on a on-mobo port, and about 180 us for 8 axes on a PCI card. How "fast" can it control motion? I'm not sure what that even means. But, I'm a servo bigot, so I don't myself use systems that use step/direction pulses. Software-generated step pulses certainly can be a limit, especially when used with a step/direction servo drive and a high resolution encoder. I think that is what you were actually asking, but that is not a parallel port limitiation, but a limitiation of using software to send individual step pulses. There are other ways to use the parallel port, such as a communication medium between the computer and a controller device. Jon ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
