S-Hub represents a device which allows connecting RS-485 sensors to Poseidon Family units. The RS-485 bus is connected to the Poseidon model 1250 via TP cables and RJ45 connectors.
S-Hub allows connecting up to 8 sensors over RJ45 to a single Poseidon unit. S-Hubs can be connected in series. Though S-Hub's topology can be found similar to Hub on Ethernet it cannot be commuted.
The RS-485 bus works reliably even over long distances in industrial environment but some principles must be obeyed when making a connection. To make sensor connection easier we supply the S-Hub along with the Poseidon. That is really a great help when it comes to installing sensors.
Standard TP cables in the star connection can be used.
A scheme of specific application with one S-Hub can be found for example in Poseidon 1140 - Application: Example 02
Advantages of using S-Hub for RS-485 sensors' connection:
- Simplification of cabling (mainly in larger installations)
- Using popular RJ45 sensors
- Easy extension with more sensors
- Simplified power supply connection for individual sensors. Power supply is connected directly to the S-Hub unit. It is possible to use standard power adaptor.
Connecting sensors over RS-485
Generally, the sensors communicating over RS-485 bus can be connected in serial connection or, using S-Hub, in star topology.
For this connection you don't need an S-Hub. The individual sensors are interconnected directly. Sometimes this connection is called a Daisy chain. It is sufficient for large buildings and long distances.
- Connection via 4 wires (for RS-485 we recommend twisted pair)
- Full wiring length cannot exceed 1000 meters
- For more than 3 sensors it is necessary to increase power supply of these sensors
- The last sensor must have the RS-485 line terminator turned on (option "LAST")
Connection with S-Hub
All sensors are connected in one place, working with RJ45 connectors only, S-Hub is located in the centre of the structure.
Principles for using S-Hub
- Connecting with four-pair TP cables
- Full wiring length (sum of all RS-485 cables) cannot exceed 500 meters
- Sensors must be connected to the S-Hub subsequently from port 1 to 8 without empty slots between sensors. See picture
- For connection of more than 3 sensors or longer wiring we recommend connecting power supply of the sensors via S-Hub as depicted above. The LED signalizes power supply from the RS-485 input (green light), or external power supply connected to the unit (red light).
- The jumpers of the last sensor must be set to "LAST" position, all others set to "MIDDLE".
Each sensor connected over RS-485 must be equiped with a unique address (here it's A - F). S-Hub units can be multiplied in series but it's always necessary to verify configuration of the last sensor with its jumpers set to LAST.
A more difficult application is connection of 10 sensors and
The"J" sensor is the LAST, other sensors set as "MIDDLE". Note that the middle S-Hub does not need power supply, while G and H are powered as well as sensors A - F from the first S-Hub unit. Sensors I - J are powered from the third S-Hub unit.
B-Cable - RJ45 / 4. wire connection
Some of the supplied RS-485 sensors already have an RJ45 connector but others have only 4 terminals marked A,B,+,- .
To connect these sensors to the S-Hub you can use the B-Cable module or connect it directly to the RJ45 cable (connection scheme).
..more about the B-Cable
What to do when the RS-485 bus does not work
If you don't use connection using the S-Hub and original supplied connectors, you can encounter problems with some sensors or the whole sensor network. When problems appear, check the following:
- Check whether it all works on a table, within short distance and in ideal conditions.
- Check sensors' IP address configuration if several sensors do not work properly, more sensors cannot use one same address.
- Wiring with length of more than several meters must be terminated so check the termination resistance on the last sensor or if a jumper or a DIP switch has TERM=ON.
- The RS-485 conductors must be differentiated. Check whether A wire leads to pin A, B wire to pin B. In an idle state the voltage of the A should be a little higher than of the B one.
- When using TP cables (RJ45), note that all sensors have the green cable connected with the white stripe cable (white-blue). Check this connection on all cables where the B-Cables weren't used.
- If using additional power supply for the sensors, use a galvanicaly insulated source. Sensors have little power consumtion so it is possible to lead the power over TP cable for tens and even hundreds of meters.