RS-485

[Greg 0]

Hi to all, Could any one give me please link or a PDF how to weld a RS485 connector(Half and Full duplex)? should be used for modbus communication. Thank in advance. Best Regards, Greg. Edited 24 Jan 2011 by Greg

[Mickey 71]

Your request will depend on the device your are trying to connect to. Provide the complete catalog number(s) for all devices on the network. http://www.google.com/search?q=RS485&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a#hl=en&client=firefox-a&hs=7tT&rls=org.mozilla:en-US:official&q=rs485+pinout&revid=644789457&sa=X&ei=7OE9TfW8EIWosAPbrZy2Aw&ved=0CIkBENUCKAA&fp=8ce0e008a607e93d Edited 24 Jan 2011 by Mickey

[paulengr 44]

Half and full duplex doesn't make any sense. See www.modbus.org. Modbus uses between 2 and 4 wires depending on the particular implementation. There is no "standard" connector. Quite often it's just a terminal strip. "Half" and "Full" duplex are terms for RS-232 communication to modems coming from the teletype days. In full duplex mode, quite often you couldn't see what you typed because anything that you type got sent to the other (remote) end. With half duplex, it not only sent the character to the remote end, but also echoed it back on the printer (and later, CRT) that you were typing on. You COULD echo it from the remote end as this provides feedback if something is messed up but in a time where the return path might be several seconds long, most folks opted for speed of feedback over the obvious advantage of cross-checking what you sent vs. what you received back. Of course for something entirely "electronic" such as Modbus and in almost all modern systems especially when baud rates have progressed well past the days of 150 or 300 bps, half duplex (echo) makes NO SENSE at all. One would never use "half duplex" for Modbus or pretty much any other serial protocol intended to be interpreted by a machine, let alone humans in the day when 9600 bps is now considered "slow". I can just barely speed read at 2400 bps...anything higher is just a blur. So to answer your question, I first suggest you head on over to www.modbus.org and download a copy of the standard. Then carefully research the details of the connectors of the specific devices you have. Then it should be pretty obvious which wire goes where because the labelling should be similar if not identical. About the only complicated detail is when you have to interface a device that expects a different number of wires. Fortunately the modbus site is pretty good at outlining these cases and explaining them.

[ianbuckley 0]

Full duplex vs. half duplex is just a matter of whether both devices can be sending and receiving at the same time (full duplex) or one is sending and the other receiving (half duplex). RS485 can be half duplex (2-wire) or full duplex (4-wire). The attachment has the pinouts you need. Make sure you do not mix connections between a 2-wire and a 4-wire device. Ian Modbus_over_serial_line_V1.pdf

[Mike Lamond 1]

I'm not sure what hardware those pinouts match, except that the diagrams resemble parts I've used with Modicon Momentum processor adapters. Here's what I've connected lately: ABB SC300 DCS Controller: DB-15 male Emerson DeltaV Serial I/O module: terminal strip (RS-232, RS-485 4-wire or RS-485 2-wire) GE 90-series CMM module: DB-25 female (RS-232 and RS-485 combined) Various RS-232/RS-485 converters: terminal strip Some Modbus/BACnet interface device: terminal strip This is why we get the big bucks to be system integrators! Mike

[Greg 0]

Guys thank you all! its very helped me.