drbitboy
Lifetime Supporting Member
Is There a standard wiring for modbus RS485 RTU two wires ?
- Thread starter widelto
- Start date
TheWaterboy
Lifetime Supporting Member + Moderator
That is fact
widelto
Member
OP
@Waterboy:
Hi, do you have any document where I can see what I Should be aware of. ?
In my case everything is going to be controlled only by a Siemens PC S7-1500, should I be aware of "masking" in my situation. ?
Last edited:
TheWaterboy
Lifetime Supporting Member + Moderator
Rotork Publication PUB091-003-00_219 Page 59
widelto
Member
OP
@Waterboy:
My application uses MK3 instead of MK2.
And Thanks anyway , I will not use any terminal input to the actuator, I will use it exclusively thru Modbus RTU.
By the way, this application is for an aqueduct.
Regards,
widelto
My application uses MK3 instead of MK2.
And Thanks anyway , I will not use any terminal input to the actuator, I will use it exclusively thru Modbus RTU.
By the way, this application is for an aqueduct.
Regards,
widelto
widelto
Member
OP
It is finally working
From Siemens web page:
Note
If you use an RS485 connection cable or an RS422 connection cable that is longer than 50m, you should add a terminating resistor of approx. 330Ω.
Exceptions here are the modules CM 1241 and CB 1241 with other terminating resistors.
They only terminate the two ends of the RS485 network. The devices between the two terminal devices are not terminated.
1)Terminator should be 330 ohms for distances greater than 50 meters, (Modbus standard is 120 ohms)
2) If distance is less than 50 meters no terminator is use on any end. That was my case because I was testing ROTORK valves actuators at the office.
See attached figure.
I am supposed to setup the whole project, maybe this afternoon or tomorrow, I will need to buy 330 ohm terminators , my whole distance is grater than 300 meters.
From Siemens web page:
Note
If you use an RS485 connection cable or an RS422 connection cable that is longer than 50m, you should add a terminating resistor of approx. 330Ω.
Exceptions here are the modules CM 1241 and CB 1241 with other terminating resistors.
They only terminate the two ends of the RS485 network. The devices between the two terminal devices are not terminated.
1)Terminator should be 330 ohms for distances greater than 50 meters, (Modbus standard is 120 ohms)
2) If distance is less than 50 meters no terminator is use on any end. That was my case because I was testing ROTORK valves actuators at the office.
See attached figure.
I am supposed to setup the whole project, maybe this afternoon or tomorrow, I will need to buy 330 ohm terminators , my whole distance is grater than 300 meters.
TheWaterboy
Lifetime Supporting Member + Moderator
The same rules apply to MK3. I was converting some from discrete open/shut control to MB proportional, so I had to deal with these and it wasn't very intuitive.
widelto
Member
OP
@Waterboy :
Thanks for your advice, my question is :
In my case that my applications states that valves are normally close or normally open , should I need to be aware of masking.
As I mentioned, I only use Modbus to open close and diagnostic valves.
Thanks for your advice, my question is :
In my case that my applications states that valves are normally close or normally open , should I need to be aware of masking.
As I mentioned, I only use Modbus to open close and diagnostic valves.
TheWaterboy
Lifetime Supporting Member + Moderator
As I now recall, on the MK3 there is a 'preference' you can set from the GUI menu that will handle this. If its working through MB as you like, you are good.
In my app I had had contention between the commands given through the discrete inputs and the MB commands and you need to tell the Rotork which to use when that happens.
In this case there was a local "Oh ****" button to close the valve and that needed to take precidence over the modbus command when it was invoked.
In my app I had had contention between the commands given through the discrete inputs and the MB commands and you need to tell the Rotork which to use when that happens.
In this case there was a local "Oh ****" button to close the valve and that needed to take precidence over the modbus command when it was invoked.
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