AD Modbus ETH Gateway to ML1500 via ENI Interface... HELP!

[TimD]

Hello,

I have an Automation Direct Modbus-to-Ethernet Gateway on the same netrwork as an AB NET-ENI Ethernet-to-Serial device.

The Modbus has one slave, a Flow Meter, data is coming in fine to the Gateway.

The ENI has a routing table configured with IP of Modbus GW and written into ROM of the ENI.

The ML1500 has a MSG block, (500 CPU Read) with node address as 45 (IP/Route of Modbus GW in ENI Table)

Unfortunately, I can't map my destination address as an AB standard, like N7:0 ... The AD GW has simple addresses like 0,1,2 etc, which obviously, I can't compile/download because of errors.

Anyone ever have to do this... and get it to work?

Any help appreciated.

Thanks,

Tim

 

[TimD]

OK, so I found out my ML1500 is capable of being a Modbus Master om port 1, the 9-pin DB-9 (rectangular)

Anyone have a pinout for connecting TXA, TXB and GND to this port?

This seems like a faster solution...

 

[Ken Roach]

The AD device is Modbus RTU to Modbus/TCP.
The A-B device is DF1 Full Duplex to EtherNet/IP.

There's your incompatibility; the serial and Ethernet protocols are simply different.

Is the basic goal just to get the Flowmeter data into the MicroLogix 1500, or do other devices need to be involved ? What's the physical distance between the MicroLogix and the flowmeter ?

 

[TimD]

Ken, Just want to get one MB device into ML1500.

I just discovered that my 1500 Firmware allows Modbus Mastering on Port 0 and 1! Port 0 is occupied, port 1 is open. I've already changed comms config to Modbus Master for port 1.

I can make a serial cable, but the cable pinout specs I have do not show RS485, or at least the TXA/B/GND I'm used to seeing... Is it TXD/RXD and GND?

Thanks

 

[bernie_carlton]

You will need the 1761-NET-AIC to convert RS232 to RS485. Other thrird party convertors may work also, but this is what we use.

 

[Ken Roach]

Is the Flowmeter an RS-485 device ? Your description of "TXA and TXB" suggests that it is, rather than "TX and RX" for RS-232.

You probably only need an RS-232 to RS-485 signal converter. The A-B 1761-NET-AIC is my standard one, but hundreds of different ones are on the market. One favorite vendor for these is B&B Electronics; they know their technology well, build durable devices, and ship promptly from the Illinois.

 

[TimD]

Yes, the FM is RS-485

So, Just because the controller has Modbus, It dosen't have RS-485 capabilities, just 232?

If so, that's what I'll get, a converter from B&B or AB. Thanks Bernie and Ken.

If there IS a way to wire 485 directly to port 1 of the ML1500, let me know!

One final question, How come on a 1400 and 1100, I can do RS-485 directly off the port pins without a converter? I know the 1500 is an older model, is that the reason?

Thanks Again!

 

[bernie_carlton]

The 1100 and 1400 DO have RS485 available.

 

[TimD]

Thanks Bernie, I learn something new every day!

So, if I get the converter, I just read Modbus address in Flow meter as 40001 etc? The converter just electrically changes 485 into 232 and the rest is transparent?

 

[Ken Roach]

That's right; the signal interface converter just changes RS-232 to RS-485 voltage and signal levels. The protocol is Modbus RTU, no matter what sort of media it travels over.

The MicroLogix model numbers aren't sequential to the release history; the 1500 was actually the second model of MicroLogix, released in 1999.

The modern MicroLogix 1100 and 1400 benefit from evolution, having onboard Ethernet, embedded RS-485, onboard LCD interfaces, Modbus and DNP protocols, more RAM, and online editing in the operating system.

 

[TimD]

Thanks, Guys.

I ordered a NET-AIC module just to give AB some extra money I talked with B&B and am getting a multi-use converter for the tool bag, for the next time