I'm impressed with your answer. I recognize that I didn't have idea about cable pairing in order to improve noise immunity.
I will take care of this, and put a section on the web to comment on this. I wonder if you have also a Eurotherm 631 driver, because you seem to be very familiar with our setup. I've reviewed the information regarding resolvers, and yes, you are right again. The motor has a resolver and the signal it produces is translated to quadrature encoder signals by the driver. I tried to figure out what kind of resolver it uses, but I found only that it is a "2 pole Eurotherm transmitter resolver", no references in Eurotherm web page. So I don't know if the signal is transmitted analogically or digitally from the resolver to the drive (just curiosity). I have configured the quadrature signal in the drive to be 4096 steps per revolution (the maximum possible at the drive). So I don't know how confident can I be about the accuracy of the quadrature steps given by the drive. In a quadrature encoder of the type based on printed disk, with the same amount of steps per rev, I think you can be confident about the accuracy being +-360/4096 degrees, provided that the disk has been printed OK, it is well attached to the shaft and that no meaningful vibrations affect the sensors (I think). But I'm not sure the induced currents in a 2 pole resolver can be that accurate when related to the angle. I mean you can generate 4096 per rev quadrature steps based on an imprecise periodical and continuous analog signal, if you have a decent 12 bit A/D converter, but this does not necessarily implies that the quadrature signal generated is accurate at all. The only advantage I see to a resolver against a quadrature encoder, is the former being able to give a continuous signal, so a good A/D (say 16 bits) will allow you to implement a more precise PID when the motor is at zero velocity. But this advantage will only noticed if we can read directly the analog signal given by the resolver, something that I judge difficult to do in our setup. I'm thinking (in a future arrangement) about placing linear encoders along the guide, avoiding the possible imprecise measurements given by the resolver, and the imprecision associated to the backlash between rotary and linear motor. Feel free to comment on any of the above. I'm just speaking (loud) about my lack of knowledge regarding the fine details needed to tune or design a good machine for CNC. Thanks very much indeed Javier > I agree that the pins on the x40 connector are connected to the > corresponding pins on the motenc-100 terminal board. You can, however, > improve the noise immunity by rearranging the wires on *both* ends of > the cable. > > http://www.imac.unavarra.es/parallel/images/argazkiak/DSCN1697.JPG > > In this image, B+ and B- are connected to the blue/blue-white pair, so > the B channel signal has added immunity from noise and crosstalk. On the > other hand, the A channel and X channel signals are each split between > two pairs, so neither receives the benefit of running over a twisted > pair. If you can remake the RJ-45 end of the cable, you can put each > channel on its own pair and get additional noise immunity. That was > what I was trying to say earlier. There's a writeup on balanced signals > and twisted pair here: > http://www.duxcw.com/digest/Howto/network/cable/cable4.htm > > Regards, > Jim > > > > ------------------------------------------------------------------------- > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier. > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
