ProfiHub B2FOR+ fiber MM ring coupler PROFIBUS

The ProfiHub B2FOR+ functions as an enhanced PROFIBUS optical-to-metallic converter with two ports on the metallic side to create two galvanically separated segments. This prevents interference or a bad signal from reaching the other segment and thus affecting the signal quality in the other segments.

Thanks to diagnostic LEDs on each segment, it is possible to detect a fault before PROFIBUS stops working. Each segment is equipped with a CANON SUB9 connector, which serves perfectly as a measuring point for connecting e.g. the ProfiTrace 2 diagnostic tool.

Need a Single-Mode or Multi-Mode option?

Optical devices can be interconnected with either single-mode or multi-mode fibers. Find out first which type of optical fibre you are using. If you confuse this when making your selection, the multirepeater may not work properly.

Main advantages

• Behind the optics you create 2 galvanically separated metallic segments.
• You can create a circle, point-to-point, star or tree topology.
• Includes redundant power supply with alarm relay contact in case of secondary power failure.
• Installation does not require a change in the PB Master's HW configuration.
• A CANON measurement port on each metallic segment allows you to connect a PB tester and measure each segment separately.
• LEDs inform about the communication status (OK, ERROR) on each channel.
• Automatically detects PB baud rates.
• Obtains diagnostic information from the ProfiHub slave device.
• Can be interfaced with the ComBricks system.
• Provides an overview of the PROFIBUS network topology.
  
  
  

ProfiHub in combination with ComBricks as a diagnostic tool

ProfiHubs B2FOR+ and B4FOR+ are comparable to Siemens OLM converters, but unlike OLM they can create more galvanically separated PB segments and provide the possibility of implementation in ComBricks system. With ComBricks we can read diagnostic information from each ProfiHub connected to the ComBricks system.

With this feature, we have much more insight into the real network topology than we have had so far. This is because each ProfiHub will show us what stations are connected on each channel. It also has a Robust feature, which means that if illegal messages appear on any of the segments, it will not pass them to other segments (see Figure 1). Of course, it will show us on which segment the messages have been corrupted, and thus we can quickly find out what part of the network the problem is and also start solving it quickly so that there is no unplanned downtime.

Figure 1: Preview of ProfiHub B2FOR+ in ComBricks

What topologies will you create with it?

The ProfiHub B2FOR+ is suitable for use when creating or upgrading PROFIBUS DP optical networks because it allows you to create topologies of the following types:

• ring,
• point-to-point,
• star
• tree.

PROFIBUS ring topology supported

Unlike the older ProfiHub B2FO2+ type, this ProfiHub B2FOR+ can be connected to the PROFIBUS Ring, i.e. a ring topology.

Previously, we only used ProfiHubs for network branching (splitting into multiple segments), i.e. we were creating a clearer network topology and making the network more robust. With this new ProfiHub we can also create a clearer topology, make the network more robust, but at the same time we have the possibility to connect the network into a ring.

A ring topology creates redundant connections, so it is typically used where there is a costly and lengthy process to re-hire a link after a communication failure.

How will you know if the PROFIBUS ring is open?

If we have a network connected in a ring and one of the ring threads gets disconnected/damaged, we need to know as soon as possible. The network will still work due to the circular wiring, but only in line. And if there is another disconnection/damage to one of the fibers, the PLC will lose some of the devices and the line will stop. Conversely, when we get a notification of a ring disconnection, we can promptly replace the damaged cable and there can be no communication failure.

ProfiHub B2FOR+ provides us with a ring diagnostic LED that is located directly on the multirepeater. But LED diagnostics can often be insufficient, so ProfiHub provides us with the option of interfacing with the ComBricks system.

For interfacing, we will need the appropriate number of BxFOR+ ProfiHubs, Headstation ComBricks, and a FOR-MM1/FOR-SM1 ComBricks expansion card (see Figure 2).

Figure 2: Example of monitoring and PROFIBUS network topology

ComBricks will monitor the overall state of the ring in this way. In the case of a violation of one of the optical links, we will immediately receive information that the ring is disconnected. We also get information on which port ProfiHub has no signal (link down). This means that we immediately know which optical link is damaged and can replace it quickly. Information about the status of the ring is displayed on the ComBricks web interface. In ComBricks we can also configure an email notification and receive an email when the ring is disconnected.

Figure 3: Preview of ProfiHub B2FOR+ in ComBricks

Truly perfect galvanic isolation of all PROFIBUS segments

1. The improved electronics of the ProfiHub multirepeater allows (unlike competing repeaters) unlimited cascading in succession (so the maximum number of 9 repeaters in a cascade does not apply).
2. The ProfiHub has 100% short circuit protection, i.e. if you short the A/B wires in segment 1 with respect to each other, this short circuit will not pass to the other segments. This behavior is logically expected from a repeater, but unfortunately does not apply to many other repeaters on the market.
3. In addition, the data on the network is constantly monitored for the presence of skew, which ProfiHub digitally smoothes out. We know from our customers that they prefer ProfiHub multirepeaters precisely because of the better galvanic separation of all segments, which has minimized outages on PROFIBUS networks.
   
   

Why should you shorten PROFIBUS segments?

In our experience, we recommend that customers do not have up to 31 PROFIBUS stations per segment, because 31 stations means 31 potential causes of problems that can cause signal reflections in the PROFIBUS cable. This reflection increases with the length of the segment and eventually becomes so large that it usually shuts down the farthest station.

We therefore recommend that our customers deploy a maximum of 5-10 PROFIBUS stations per segment. In practice, this means that you bring the signal from the MASTER station into the ProfiHub multirepeater (you can then continue further) and connect a maximum of 5-10 stations to each segment. It can be

• about stations always in one switchboard,
• o stations in one direction from the switchboard,
• o all inverters / IO peripherals / HMI panels etc.

ProfiHub works like a hub, so it connects everything to everything. It doesn't matter what stations you connect to each channel (segments).

This strategy of dividing the network into smaller segments with fewer stations not only significantly increases the robustness of the PROFIBUS network, but also shortens the time to find a fault in the event of a problem with the PROFIBUS network, because the cause and effect can usually be found in just one segment.