i have 1 PLC and 6 devices which talks Modbus RTU via RS232 or RS485 port. The Allen Bradley PLC needs to gather the data from all 6 devices over wireless.

can someone pls advise the best and reliable way to achieve this?

 

You need to post more information...

Does the PLC have an ethernet port (E/IP)? or do you need to use the serial port on the PLC?

max. distance between PLC and devices?

How many Modbus RS232 devices? Or can all do RS485?

 

Ok. Yes the PLC have Eth port ready. I prefer to use TCPIP. Max distance is 50 meters only. The devices can be ordered to have either RS232 or RS485. So, yes all can support RS485.

 

Not sure why you need to go wireless...
I assume that the devices are close to each other and thus can be connected by use of RS485.

I would set up the PLC as EtherNet/IP scanner (master) and use a wireless bridge a gateway (ethernet/ip adapter to Modbus RTU master) to read/write to the Modbus devices on RS485.

If you can skip the wireless, set up the PLC as Modbus RTU master (RS485) and run a cable to the devices..

just my 2 cents

 

Hi Patrick,

Normal cabling is not an option due to blockage. Can u confirm my understanding. U suggested a combination of Ethernet/IP wireless bridge AND a Ethernet/IP Modbus RTU gateway.

So for my application, i would need 6 Modbus Rtu gateway plus 6 wireless bridge for all 6 instruments. I also need 1 wireless bridge at the PLC side.

 

Hi Dinster,

Ok, I understand.
Now mind you that I am bias since I work for HMS, but this is how I would solve it:

6 gateways (AB7007, Ethernet/IP slave to ModbusRTU master)
http://www.anybus.com/support/support.asp?PID=110&ProductType=Anybus Communicator

7 Wireless bridges (021430-B,Bluetoth), where 1 is set up as master or access point.
http://www.anybus.com/support/support.asp?PID=486&ProductType=Anybus Wireless Bridge

or, If the PLC can be set up as Modbus TCP master:

6 gateways (AB7702, Modbus TCP slave to Modbus RTU master)
http://www.anybus.com/support/support.asp?PID=237&ProdType=Anybus X-gateway

7 Wireless bridges (021430-B,Bluetoth), where 1 is set up as master or access point.
http://www.anybus.com/support/support.asp?PID=486&ProductType=Anybus Wireless Bridge

If you want a illustration or have any questions, you can also contact me at: [email protected]

//Patrick L

 

Another option is to utilize Ethernet Gateways. I personally use EGX100's tie them to a regular wireless router. You may have to do the same for the PLC.

I know you need wireless between the PLC and your devices but can your devices be chained via RS232/485? If so that can lower the number of gateway's you need.

http://www.powerlogic.com/product.cfm/c_id/6/sc_id/18/p_id/34

EGX100--I know it is listed as a power logic device but it works with any modbus device.

Hope this helps.

 

There is a ZigBee based solution, which does support Modbus RTU slaves from a Modbus TCP master. This module is the host that can connect via TCP, ZB-2570-T. The TCP master connects to it. http://www.icpdas-usa.com/products.php?PID=3700 The RTU slaves can go on the more cost effective serial only client modules, ZB-2551-T, http://www.icpdas-usa.com/products.php?PID=3928 .

 

Yes You can use Rs 232 Interface radios. You can visit www.prosoft-technology.com for product RLX-IFH24s which meets your requirement.

 

I have a Modbus RS485 Controller Panel which need to be connect to a TCP/IP PLC system...
please how do i goes about it?


but i was able to purchase a device USR-N510s(serial to internet converter)

 

Welcome to the forum! Please note that it's better to start a new thread to ask your question than to resurrect a decade old thread that is only slightly related to your question.

But to answer your question, there are a few options to convert between RS-485 Modbus (presumably Modbus RTU) and Modbus/TCP.

1. A Modbus Gateway
   1. A gateway device requires the user to configure register mappings for all Modbus registers that will be accessed through the gateway. The registers from each port are typically mapped to an internal database on the gateway.
   2. Both ports communicate independently from one another and requests are responded to immediately using the data from the gateway's internal database.
   3. A gateway allows remapping, or changing, the register definitions and can be used to emulate other Modbus devices.
   4. An example of a Modbus gateway is the ICC ETH-1000.
2. A Modbus Router
   1. These devices require minimal configuration and simply repackage the Modbus messages from one encapsulation to the other.
   2. Routers introduce a small delay in the messages, as it takes time for the router to receive the message, de-encapsulate it, re-encapsulate it, then send the message.
   3. An example of a Modbus router is the Moxa MB3180 (note that this device actually supports both router and gateway functionality).
3. A Serial to Ethernet Converter (that supports Modbus)
   1. This solution is similar to a Modbus router, but is a more general-purpose device, usually capable of converting any serial communication to Ethernet.
   2. The converter must state that it supports Modbus TCP to Modbus RTU conversion. This will not work otherwise, as the converter would simply wrap the Modbus RTU packet in a TCP frame (which is a different version of Modbus usually called "Modbus RTU Over TCP").
   3. The PUSR USR-N510 is an example of a serial to Ethernet converter that supports Modbus.

Here are a couple other threads that talk about using a USR serial to Ethernet converter for Modbus:
https://control.com/forums/threads/modbus-rtu-to-tcp-ip.50764/
https://control.com/forums/threads/modbus-rtu-to-modbus-tcp-converter.50406/