Den Fredag, Januari 01, 2021 06:03 CET, skrev Chris Albertson <[email protected]>: I don't know much about RS485 but I did read that the current return path is required. You should be able to send and about 100K up to 4000 feet.
RS-485 use differential signals, currents flowing in differention directions so return path is in the other conductors. A termination is needed, should be easy to find how it should be made ib internet once you know it's needed. I'd use a section of Eithernet cable because I know it is twisted inside. I don't know the best way to provide a "return path for all voltages" Pretty sure it's a very good cable, just make sure the differential signal pairs are twisted. Used a PLC with RJ-45 connectors for RS-485 communication, there might be a standard way to assign pins then using RJ-45 connectorts, I know there is for other connectors. If this is going through optical isolators,I see a problem the signal voltages are like RS232 −7V to +12V. The optos are going to do 0 to 5 volts with is usually very marginal. Your isolators are builtin into som hardware you use? Otherwise I might be able to recommend other isolator technology I found worked well, do not manufacture semiconductors and have no interest to sell them. On Thu, Dec 31, 2020 at 8:05 PM Gene Heskett <[email protected]> wrote: > On Thursday 31 December 2020 20:10:35 Chris Albertson wrote: > > > Now is the time to connect the digital scope and see what is actually > > on the wire. Is the data bad or is the receiver unable to read good > > quality 38400b data? > > > > This is differential data, it should be able to go half a kilometer or > > something like that. Is it actuary using a twisted pair of wires and > > is there a good logic ground? > > > That I doubt. Its a 2 wire cable, so any logic ground is coming thru > other cable from the 5i25, thru the interfaceing and back to the ACM > terminal. DCM could be grounded but is not, and everything on that > circuit isvia the opto's isolating the spindle outputs of the 7i76D. > > That stuff is still hooked up, but could be disconnected as its no longer > actually controlling the motor. There does not appear to be a ground > reference for the rs485 signals called out in the sample wiring diagram. > There is an earth ground in addition to the 2 wire single phase input, > and its connected back to the static ground in the service box. > > > It's easy to see if the cable is the cause. look at the bits on the > > cable end, then remove the cable and look at them in the output port. > > The only way I can access that would be to back the pins out of the term > strip far enough to put the scope probe hook onto the Hilitchi pin. The > scope is plugged into a different circuit entirely, so its ground > reference is bound to have some noise on it. I can set the scope to > combine the 2 signal wires into a differential, but having done that, > the serialization of the samples quantizations can easily be seen. I > should probably do that, if for no other reason than to confirm the baud > rate matches going both ways. I have previously caught the pc lying > about the actual baud rate its generating. Depending on the individual > driver, it might be fixeable but haven't tried. From an lsmod: > usbserial 31410 3 ftdi_sio > and I've not had previous experience with the ftdi_sio being off. > > Since the lags can be gotten used to, I might just leave it at the slower > speed as that seems to be bulletproof so far. > > Thanks Chris. And a Happier New Year to all. > > 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
