adding 4 wires stuff in a 2 wires modbus com


Thread Starter


I want to add five sepam15 in my modus communication network (a PLC S7-315 with cp340-rs422/485 card linking 20 PowerQ).

I actually use 2 wire ASCII alf/duplex com with powerQ

The sepam15 request 4 wires com.

so i need a 2 wires - 4 wires converter (is this stuff exist?) and what other change in my communication protocol?

John Mutchler

The CNV100 is a 2-wire to 4-wire converter often used in Powerlogic daisy chains, including those with Sepam relays.
Their is not much difference between the two and 4 wire system... (I believe it mostly about speed of transmittion between a Half and fully duplexed signal...)

You should be able to connect the (A channel Tx and Rx) and the (B channel Tx and Rx) together on the 4 wire system to convert the whole system over to Two wire... But, if you have your heart set on a converter to bridge the two system devices, you can purchase one from B&B electronics... Their on the web...

Purchase a "Model 485OP" RS-422/RS-485 optical isolator repeator... They will provide you with detailed instructions on how to convert a 4 wire system over to a two wire system... Or the other way around... Once you see the diagram, you'll see how simple it truely is...

good luck..
thanks for the advice.

i found a converter (BDC485R2 from equiptrans).
i prefer using converter, i already have some communication problems with the power Q. i don't want to experiment too much.