On Sat, Feb 02, 2008 at 08:26:31PM -0800, Kirk Wallace wrote: > http://pinouts.ru/SerialPortsCables/rs485_cable_pinout.shtml > > I plan on building a couple for my SJ200 application, and if you want I > can make an extra and send it over. I'm not sure when I'll have time to > build and test it -- probably in the next couple of weeks. Let me know.
Hi Kirk, Though it looks like you're onto alternatives by now, it may be worth noting that there's no separate network ground wire in that design. From http://www.embeddedsys.com/subpages/resources/images/documents/microsys_art_RS485.pdf , I'm planning to follow: "The RS-485 specification recommends connecting a 100 ohm resistor of at least 0.5 W in series between each node's signal ground and the network's ground wire, as Figure 1 shows. This way, if the ground potentials of two nodes vary, the resistors limit the current in the ground wire." Admittedly, that's defeated if local ground goes back through the power supply, to mains earth. Incidentally, the R9 + R12 bus bias chain is in parallel with the 120 ohm R13, for bus termination purposes, giving under 86 ohms. (R13 = 200 ohm would give a 120 ohm result) They're certainly biasing the bus heavily, which is good for noisy environments. (Thanks for the link. It's educational to see what others do.) Erik ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
