On Thursday 22 October 2020 07:55:04 andy pugh wrote: > On Thu, 22 Oct 2020 at 02:00, Gene Heskett <ghesk...@shentel.net> wrote: > > No, that steers the pwm which modulates the bottom half of the > > bridge, and not externally separated, both sides on these full H > > bridge cards. > > The step outputs are a differential pair, not PWM and /PWM. I am not > sure if that is a real distinction. > But you might need to be careful of the common-mode voltage limits of > the differential pair driver on the 7i76.
The output swing of the stepgen outputs, both step and dir, is rail to rail, with the rail at around 5.1 volts. I've no reason to believe the corresponding inputs are any different. For the spindle encoder, which I inadvertantly bought with differential outputs, has a pair of rs485 teeny boards, rigged as rx only, making rail to rail out of that diff pair. Works flawlessly at speeds that cannot even begin to get thru the input opto's on the average bob. Clue? The spindle tach dies, and the pid drives the spindle wide open at speeds above 400 revs. The 7i76 encoder inputs have no speed killing opto's. So it Just Works. This motor I'll use on the BS-1, has a maximum of 5.4 Kilohertz, pushing the opto's speed limits a bit but should work. If needed, I can bypass the opto's on the bob, the need yet to be determined. NBD IOW. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
