Hello,

I am designing an automation solution where I have 40 Electrical valve acuators to connect my PLC. I am considering two types of actuators with different communication technology.

Solution 1: Modbus TCP/IP
Solution 2: DeviceNET, Profibus DP and Profinet (Not quite familiar with this)

These 40 actuators are spreaded across the plant with various distance and problem here is the unknown distance. What PLC and communication protocol should I be using to design this?

Please share your thoughts.

Thanks in advanc,

 

Can you eliminate one or more alternatives on the basis of cost?

 

Yes, I can. As I said in the post, I am more comfortable with the Modbus TCP/IP protocol w/ Allen Bradley PLC but not sure about its limitations? Is there any limitations on distance or number of devices I can conntect using Modbus?

Also at this point I am pretty much open to anything as this project is only in design stage right now.

Thanks,

 

You might find a better PLC than AB, but you won't pay more for it. (AB in-joke, at least among the engineers. Marketing guys -- not so much)

As for DeviceNet your can find a wide array of vendors that make the I/O devices that can hook to the network. You have 3 potential optimizations with the network:

1. You can have a total trunk length of 500 meters if the network speed is 125 KBits/second
2. You can have a total trunk length of 250 meters if the network speed is 250 KBits/second
3. You can have a total trunk length of 100 meters if the network speed is 500 Kbits/second

 

You might find a better PLC than AB, but you won't pay more for it. (AB in-joke, at least among the engineers. Marketing guys -- not so much)

As for DeviceNet your can find a wide array of vendors that make the I/O devices that can hook to the network. You have 3 potential optimizations with the network:

1. You can have a total trunk length of 500 meters if the network speed is 125 KBits/second
2. You can have a total trunk length of 250 meters if the network speed is 250 KBits/second
3. You can have a total trunk length of 100 meters if the network speed is 500 Kbits/second

DeviceNET can be implemented on what PLCs? Any Ideas?

I am also thinking about potential solution with Profibus DP where I can decentralized my IOs with Interface modules and install it closer to actuators. I have never used any of these technologies before.

 

DeviceNET can be implemented on what PLCs? Any Ideas?

I am also thinking about potential solution with Profibus DP where I can decentralized my IOs with Interface modules and install it closer to actuators. I have never used any of these technologies before.

DeviceNet is available on AB PLCs and any of the other PLC makers who are members of ODVA (Open Device Net Vendor's Association)
www.odva.org
I know that OMRON, and Schneider (formerly Square D) were in that group at one time.

 

Devicenet had its day. You will find it relatively expensive to comply with its standards. TCP/IP is very easy to implement.

 

Devicenet had its day. You will find it relatively expensive to comply with its standards. TCP/IP is very easy to implement.

The big knock on this one is the lack of determinism. Don't know if the issue has been addressed or not. It is great for moving massive amounts of data however.

 

Not a knock, but rather application dependant. Good point though.

 

Devicenet had its day. You will find it relatively expensive to comply with its standards. TCP/IP is very easy to implement.

Isn't it speed of data decreases with long CAT5 cable using Modbus TCP/IP? I have actually seen it where Controller and HMI connected 50-100 ft apart. Is that true?

 

https://literature.rockwellautomati...ture/documents/rm/enet-rm002_-en-p.pdf#page19