Profibus Connection issue


Thread Starter



I have three profibus RS 485 cables coming from three independent standalone systems. I want to transfer information from these three standalone systems to my Main system.

The problem is the main system controller has only one Profibus RS 485 profibus port to connect.

Please note, i cannot connect Standalone systems serially at the local side (in field), and then run one cable finally to the main system controller.

Please suggest some other solutions.

The solution should be such that , if out of three profibus cables going from each standalone system to Main syatem , if one cable is broken , then also other two remaining standalone systems should still be able to transfer information to the main system.

Patrick Beckett

Within a single segment you can't have spurs in the way your describe but profibus allows for multiple segments. A repeater will re-generate the electrical signal for the downstream segment. Importantly, if the secondary segment develops a fault, or disconnect, it does not affect communication of other devices on the primary segment. There are several devices that can do this.

Procentec produce a hub which has one input profibus cable and provides 5 downstream segments electrically isolated from the incoming segment. Each downstream segment would go to a standalone device. Works a dream.

We have also used Siemens diagnostic repeaters. Run the profibus cable from your master to the first repeater and then out and onto a second repeater and finally to the end terminator. From each repeater another two segments are generated which can go to the standalone devices.

Be careful that each segment is correctly terminated at each end.

We have used both methods successfully depending on client requirements.
What you need is a mux or what we call a serial server. Find one that is protocol independent or which works with Profibus and it should work. Lantronix and Systec both provide protocol independent serial servers that use tunneling and can be used for similar purpose.

Furthermore, in your post you did not mention what type of Profibus connection you have on the stand-alone systems.