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Poseidon HW interfaces for sensor connectingIndividual Poseidon models support several hardware interfaces for sensor connecting. These interfaces along with connectors and related accessories as well as outputs of Poseidon units are described on this page.
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Port 2 - RJ12 ![]() |
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Notice: The T-Box unit supports connecting of several sensors with RJ12 connector to one Poseidon connector. They can be series-connected. Remember total maximum length of 1-Wire bus wiring (10 meters).
Industrial bus (RS-485)
Over RS-485 up to 31 sensors can be connected over distance up to 1000 meters in industrial applications. We use TP cables and RJ45 connectors for RS-485 line, it is very easy to use them for a common user.
The RS-485 bus consists of blue communication cable pair (pins 4,5), marked as A and B. Power supply 12V for sensors is conducted through the brown cable pair (7,8).
If you use delivered S-Hub unit or B-Cable module, the green cable pair (pins 3,6) is used to RS-485 bus return from the sensor to the hub unit.
- Maximum wiring length: 1000 meters of total length
- Supported sensors: Temperature, humidity, current, voltage and other sensor (>> The list of sensors)
- Number of sensor on RS-485 bus: Up to 31 sensors (see the device model)
- Power supply: 12V/120 mA on RJ45 connector
- Power consumption: Power supply from the Poseidon unit is sufficient for up to 3 sensors. Larger number of sensors must be supplied from external source, for example S-Hub unit
- Communication cable: UTP twisted pair, eventually 4-wirephone cable
- Alarm setting : Controlling of value in safe range, configurable via Poseidon Flash setup
- Sampling period: 800 ms to 10 seconds (according to the number of connected sensors, 10 seconds for 41 sensors)
- Sensor address: Manually, each sensor must have unique address (see the sensor manual)
- Sensor disconnecting detection: Yes, disconnected sensor responds "-999.9" value
- Sensor disconnecting alarm: Disconnecting of sensor causes Alarm status if sensor indicates alarm (value out of SafeRange)
Basic characteristics of RS-485
Total wiring length up to 1000 meters
- Up to 32 devices on one line (Poseidon + 31 sensors)
- High immunity against industry disturbance
- Connecting in Daisy chain, not in star topography.
- Each device must have its unique address
- Polarity of conductors must be respected
- The end and the beginning of wiring must be terminated
Line terminating
The end of the RS-485 line wiring must be terminated. Here are several methods how to achieve it:
- Internal jumper on some sensors (jumper marked as TERM or TERMINATOR)
- In case you use B-Cable reduction, choose "LAST" configuration
- Sensors which do not have jumper or DIP switch (for example DIN bar version), end the bus with external resistor staffed on the end of wiring (for example connect resistor to terminal of the last sensor).
Value of this resistor should be higher than 120Ω, for short wiring 470Ω is sufficient and you decrease power consumption of all sensors
>> What to do when RS-485 bus doesn't work
RJ45 wiring
- Standard TP cable cat5 used
- Brown pair used for power sensors
- Blue pair used for RS-485 in direction to sensor
- Green pair used for RS-485 in return direction from sensor back (details about wiring you can find on the S-Hub page)
1 -
Not used 2 -
Not used 3 /B/
RS-485 back 4 B (-)
RS-485 5 A (+)
6 /A/
RS-485 back 7 GND
Ground 8 +12V
Power Sensor address
Each RS-485 sensor must have unique address. This address can determined via various methods:
- To use original address of the sensor which is printed on a tag on the sensor (for sensors without jumpers for configuration of address only)
- To setup address with jumper for some sensors (jumpers marked A0 to A4)
- To setup address via Poseidon command (via TCP Setup). In the moment of setting sensor address, only one sensor can be connected to Poseidon unit over RS-485 bus.
Notice: The sensor autodetection can be realized not only via Flash Setup but also via TCP Setup using terminal access. The advantage of terminal setup is that Poseidon prints addresses of connected sensors and values.
Topology of RS-485 bus
The sensors communicating over RS-485 bus must be serial-connected (daisy chain). In case you need to connect all sensors from one point, to use the S-Hub unit and to connect sensor in star topology is useful.
Serial (Line) topology
You connect individual sensor with each other. This is sometimes called Daisy chain. Advantageous in large buildings over a long distances.
- Connect over 4 conductors (we recommend twisted pair for RS-485)
- Total length of wiring must not exceed 1.000 meters
- External power supply is necessary for more than 3 sensors
- The last sensor must be equipped with terminator for RS-485 line (option LAST)
S-Hub wiring
All sensors are connected to one point and you work with RJ45 connectors only. S-Hub is placed in the middle of the structure.
Special accessories
Poseidon B-Cable reduction [600 044] (details)
To transfer RS-485 line + power supply from RJ45 connector to terminal board - 4 conductors ( A,B,+,- )- Sensor RJ45 MIDDLE cable [600 233] (details)
0,5 meter long cable to connect 4 pins ( A,B,+,- ) from terminal board to RJ45 connector. Cable connection for middle sensors.- Sensor RJ45 LAST cable [600 234] (details)
0,5 meter long cable to connect 4 pins ( A,B,+,- ) from terminal board to RJ45 connector. Cable connection for the last sensor in line.Poseidon S-Hub [600 041] (details)
RS-485 line switch for 8+1 RJ45 connectors and TP cables. S-Hub can supply power to all connected sensors.
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