On 10/24/2016 3:23 AM, Gene Heskett wrote: > Opto's on the bob are a waste of protection with modern > stepper drivers as they all have their own optos for all inputs. > Properly driven, a 2M542 driver can exceed 350 kilohertz step rates. Put > an opto on the bob and it will often fall over, stalling the motor at > half that. One of them in series with a 10 kilohertz pwm signal and the > control linearity error over powers the PID's ability to keep the motor > within 20% of the requested speed. I found which one it was, pulled it > and bridged the 2 pins to bypass it, and now I get within 5% of the > requested speed without a lincurve module in the signal path, and the > PID handles that nicely. > > Cheers, Gene Heskett
I totally agree with you on optoisolation, actually. Shoot, the whole Mesa board is only $79, and since ethernet is galvanically isolated by design, it CANNOT damage the computer. Why would I spend $40 on an opto-bob on the theory that there's a 2% chance a "mystery power surge" would destroy it?? I can't really see where you'd even get a "power spike". But the AM882 (GREAT drive at a bargain price, BTW) has 5v differential opto inputs, which makes them noise-immune to induction when no common is used, and ground noise, since there's no ground. True diff pair. Again, probably was never gonna be a problem anyways. Second, I ended up with the NPN proximity sensors shown here on the top left: https://oceancontrols.com.au/IBS-0051.html Those are insidiously awkward to interface, honestly, simplest, best practice is an opto. Anode w/series resistor to +V (I used 24v system), cathode to "output". Also you can form an AND/OR gate with optos or also fanouts, and I used that. The e-stop switch not only pulls down the input pin, but also is in series with the output pin that feeds the drives' Enable pins. If the estop is opened, the opto output stops conducting, and the drives disable. Danny ------------------------------------------------------------------------------ The Command Line: Reinvented for Modern Developers Did the resurgence of CLI tooling catch you by surprise? Reconnect with the command line and become more productive. Learn the new .NET and ASP.NET CLI. Get your free copy! http://sdm.link/telerik _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
