ML1100 rs232/rs485 question

[Electrically_Bound]

I do not have any trouble communicating with an LED message sign with my ML1100 when using an rs232 connection. I use a 1761-PM02 cable with one end plugged into channel 0 of the ML1100 and the other end "butchered" to connect the RX,TX, and GND lines to the non-standard db-25 connector of the message sign. ASCII protocol is being used.

The trouble comes when I try and connect to the sign via a rs485 connection using 1763 NC01 cable and connecting A to A, B to B, and GND to GND. I have checked and-re-checked the wiring. Let's assume(to limit the scope of this discussion)that the communication settings are correct on my sign. I am transmitting data to the sign and I do not even look at data coming from the sign. The sign is set up not to send any data to the plc on the rs485 link. This whole setup is on my desk, so, for now, we are talking a communication distance of 6 feet. I have tried using and not using the jumper between terminal 1 and terminal 2 (which is supposed to internally connect a 120 ohm terminating resistor inside the 1763-NC01 cable/breakout box).

Is there anything different that must be done with the settings in the ML1100? Does the use of the 1763 NC01 make any difference to the software in the ML110? Shouldn't I be able to communicate using ASCII protocol using an rs485 connection?

Any ideas out there?

 

[Mickey]

That cable is used when you have the ML1100 port set to DH485.
You need a RS232 to RS485 converter for what your trying to do.

 

[bernie_carlton]

The MLX1100 has RS485 pins in its connector. The 1763-NC01 breaks out these pins to an easily wired interface. We have used this to communicate via MODBUS to Powerflex4 drives. We haven't used ASCII but I don't see how that would be a problem. Just for the heck of it try swapping the A - B connections.

 

[Alan Case]

Also I vaguely remember that the manual may be wrong on this unit having an inbuilt resistor. I recall checking once with a meter, but I may be wrong.
Regards Alan Case

 

[Electrically_Bound]

I have tried swapping A and B on several occasions.

 

[John Soltesz]

I would also think about my ASCII string. Does it have a correct address for the sign? We had one setup for us with 4 signs all with the same address so you could send one time and hit all 4 signs. Didn't work real well with several hundred feet between the PC and the last sign.

I'd try some messaging software on a PC via rs485 converter to check functionality of your connections.