In my PLC STEP7-400 , I am using remote I/0. At one place fiber optic cable have been used with OLM. The distance between two station where this cable is used is around 200 meters. Can't i use the Profibus in place of this fiber optic cable? As in case of damage of this cable it takes a lot of time to rectify it.

If yes , what is the procedure?

 

Be careful as the fiber may have been used for electrical isolation or noise immunity. Your PLC probably has an internal Profibus port and you will need to purchase a Profibus adapter for the remote rack. Just consult your local Siemens distributor and they will help you with the pieces you need.

Once again though, I don't think the change is worth the effort. I can't believe the fiber is going to get damaged frequently. If it does, maybe the time and cost would be better spent in improving the physical way the fiber gets to the remote rack. And you can always keep a length of preterminated fiber in your spares.

 

Yes it's not necessary fiber optic. Profibus could reach 1000m (at 9600bds).

200mt : you could have a speed of 3Mbds/1,5Mbds or you can use a repeater in case you need higher performances

 

Hello PK;
Before you replace the fiber optic section of your bus, it would be wise to ask why it was setup in the first place.

Fiber optic does not give you any advantage as far as speed is concerned, at least for Profibus. It does extend the distance limits per segment, but requires OLMs at every node, which can make it more expensive. So, why use fiber optic cable in an otherwise copper-based network?
The answer generally lies in the immunity of fiber-optic communications to electro-magnetic perturbations, caused by high harmonics from drives and motors.

You should check where in your plant this F.O. cable has been laid, and if in those sections there are large electric motors or high-power cables. If there is such a possible problem, changing to copper could induce currents in your Profibus cable that would affect your communications, even rendrer it inoperable in the worst case.

If you decide to remove the cable and OLMs anyway, since they are not recognized as nodes, there should be no impact on the topology of the network . Check if the length of copper is comfortable at the bus speed you are using (segment length @ communication speed); also remove the OLMs and length of F.O. cable from the bus parameters in your Profibus-DP configurator, so it can recalculate the Profibus time-bit parameters.

Hope this helps,
Daniel Chartier

 

where should i change the parameters and how?