ATR171-23ABC-T / Modbus RTU

adaloisio · Post by **adaloisio** » 23/05/2022, 21:45

Dear all,

I need to configure an ATR171-23ABC-T controller to communicate as a Modbus RTU Slave. To achieve that in the User Manual, topic 9. SERIAL COMMUNICATION (Pag. 23) says for enabling this function it must be set the DIP SWITCHES as the manual shows. But I can't access these dip switches in the equipment. Please tell me how can I access them and if I need to open the controller case.
Regards

Post by **Pixsys tecnico 6** » 24/05/2022, 12:23

Good morning,
For the activation of the serial RS485 must proceed to the removal the case of the controller and set the DIP as in the following image:

image.jpg

Best Regards

adaloisio · Post by **adaloisio** » 05/08/2022, 17:56

Thanks for the last answer. It was useful.

Now we have a new problem related with this communication. We have 14 ATR171 controllers connected through a Modbus/RTU bus to a Modbus RTU/Modbus TCP converter. The bus length is about 100 m. The converter is located at the middle of the bus. The modbus speed is 4.8 kbps. All the controllers are linked to a Wonderare Intouch 2017 Scada. We could connect to all the controllers except 1. Al controllers have different Modbus Node. We replace it 2 times with new ones but it doesn't work. We thought that the problem was a connection problem but 3 controllers are connected near it and works OK. We change the SERIAL DELAY Parameter to 100ms but nothing change. Is there any known issue that we are not considering?

We sent some images of the installation. The problem is with the left side controller. There are 3 more controllers at the right of this one.

Post by **Pixsys tecnico 6** » 22/08/2022, 10:43

Good morning,
Where is the device located? is it the first, in the middle or the last of the line?
From the photos I see black and green wires in addition to the two blue wires in pins 13-14.
Verify that for each device in the line/branch it has a 120ohm termination resistor connected in parallel.
Also, I would try to remove the shield from pin 15 on all devices.

Best regards

adaloisio · Post by **adaloisio** » 22/08/2022, 20:44

Hello thanks for the response.

The controller is in the middle of the bus line.
In the first time we didn't connect the shields, we decided to connect them to look for a solution but nothing change.
In the begging each branch does not have any 120ohm resistor but we decided to connect them but the communication was even worse.
The only thing that really improve the communication was slow down the baud rate from 9600 to 4800.
The green and black wire are the bus wire that runs from one electric board to the nex tone.

Regards, Alejandro D'Aloisio

Post by **Pixsys tecnico 6** » 23/08/2022, 10:31

Good morning,
The termination resistor must only be connected to the last device of each branch (at the end of the branch).
I would leave par.85 [SE.de] as default, then 20ms.
Moreover, it would seem that the cable used is not specific for RS485 communication.

Best regards

adaloisio · Post by **adaloisio** » 26/08/2022, 16:30

Thanks for the response.

Finally the problem was solved. It was a problem related with a Wonderware writing script. Besides that the cable used between electric cabinets is RS485 compliant but the connection between controllers inside a electric cabinet use standard cables.

Thanks again for your help.

Regards

Pixsys Forum