Networking AB SLC500 with 1747AIC and 1761AIC


Thread Starter


I have four Allen Bradley SLC5/03s that I need networked into two sets of two, one is for regular use the other is a backup.

My question is if I use a 1747AIC card in the PLC and a 1761AIC outside to connect an HMI, can I connect my PC to the 1761AIC or do I need another 1761AIC on the network?

There are three ports, a DIC-8 and DB-9, If the DB-9 goes to the computer and DIC-8 connects to the HMI will this work?

Additionally I need to read sensors that communicate in MODBUS485 does my MODBUS converter connect to the DH485 on the PLCs or do I need another 1761AIC before my MODBUS converter? I have not found a MODBUS converter yet is why Im asking, any suggestions on a brand would be great.

I'm a student trying learn go easy on me. ha, ha

Thanks in advance,

lynn August Linse

DH485 is a fancy RS485 bus and 100% unrelated to Modbus. As a student, I suggest that either you must already have the special equipment to do AB-to-Modbus on hand, or have a budget to buy new hardware.

I may be wrong, but I don't think this is an '8-week, 4 hours per week' project. I don't think trying to create your own DH485-to-Modbus tool is worth the effort unless you have at least 1/2 a year to learn the details, implement something, test & fix the problems.

You could buy or use a PC-to-DH485 software package & do Allen-Bradley-to-Modbus conversion on the PC. For example, most OPC packages can do this.
The 1761-NET-AIC can handle both the PC, the HMI and the DH485 Network. It may not be the fastest but it works. I assume you have two 5/03s with 1747-AICs each, and one 1761-NET-AIC. Just make sure your PC's RSLinx is configured for DH485. I've tried myself this type of arrangement. You may even use the same HMI for the 2 PLCs. Note that the address nodes must be different for each device (the PC is usually node 0).

I assume you have had successful communication with your PLCs via DH485.