AN34: Examples of using Poseidon Industrial Bus

The AN34 application example details the use of the Industrial Bus (RS-485) for connecting sensors to a Poseidon 1250 or 2251 unit. It describes in detail the wiring of cables and connectors, as well as the DIP switch settings for supplied accessories.

Some Poseidon models support sensors connected via the Industrial Bus (see the overview of Poseidon XXXX models). For a detailed technical description of the Industrial Bus, see: Interfaces for connecting sensors to Poseidon units.

Industrial Bus (RS-485)

  • Maximum cable length: 1000 m total
  • Number of devices on the bus: Poseidon + up to 31 devices
  • Power: 12V/120 mA supplied by the bus, can be boosted with an external adapter (through a S-Hub or a Spider unit).
  • Cable type: UTP (2 or 3 pairs)

Topology 1: Basic

  • The bus leads via a 4-wire connection from the Poseidon 1250 unit to two daisy-chained sensors, Temp-485 and HTemp-485. Two twisted pairs are used by the connection.
  • A S-Hub unit is daisy-chain-connected via the RJ45 jack after the second sensor, using a 4-wire connection from the HTemp-485 sensor. The brown pair is used for power, the blue pair for data.
  • Temp-485 and HTemp-485 sensors are connected to the S-Hub connectors 1 through 3 with 6-wire connections (brown pair for power, blue pair leads the bus to the device, green pair back from the device).
  • Connector 4 of the first S-Hub unit is used to connect a Spider converter with a patch cable. The Spider unit is used to connect three Temp-1Wire 10m temperature sensors and one door contact (the contact is connected to the blue pair of the RJ45).
  • A second S-Hub connects to the Spider unit output via a patch cable.
  • Its connectors 1 through 3 are used to connect the Temp-485 and HTemp-485 sensors with 6-wire connections (brown pair for power, blue pair to the device, green pair back from the device).
  • Connector 4 is used to connect a Temp-485 sensor with a 4-wire connection (brown pair for power, blue pair for the A/B signals of the bus).
  • Termination is enabled at the Temp-485 sensor using the “TERM” jumper.


Topology 2: Connecting 10 sensors to IT Bus

Eight temperature sensors and two humidity sensors are connected via the IT Bus (RJ12) to a Poseidon 1250 unit. The 10 sensors are connected using two T-Box hubs and one T-Box2 unit.

  • Bus used to connect the sensors: IT Bus

  • Total bus length: 10m
  • Maximum number of sensors: 10
  • Sensors used:
    • 2x Humid-1Wire 1m
    • 8x Temp-1Wire 1m 
  • Accessories used:
    • 2x T-Box
    • 1x T-Box2 

Conclusion:

This solution is limited by the maximum IT Bus length. It is suitable for applications that use 1 to 10 sensors at one place (one location, 19” rack cabinet, etc.)..

 

Topology 3: Poseidon Spider – bus converter

The solution combines the properties of both buses. Two Spider units are far apart, connected via a Patch cable with RJ45 modular jacks. Both Spider units connect to four temperature or humidity sensors, each with a 10m cable. One Temp-485 sensor is located at the end of the chain and terminates the bus.

  • One Temp-1Wire temperature sensor with a 10m cable is connected directly to the Poseidon unit to the RJ12 jack.
  • Six temperature sensors and two humidity sensors are connected via the IT Bus (RJ12) to the Spider units. Each sensor is connected with a 10m cable.
  • Two Spider units are connected to Poseidon 1250 with a standard RJ45 Patch cable using the Industrial Bus. Bus length is limited to 1000m.
  • The Spider unit comprises 4 inputs for external sensors and supports one sensor per connector – for a maximum of 4 sensors.
  • The Industrial Bus is terminated by connecting a Temp-485 sensor with termination enabled over a 4-wire connection. The Spiders have mutually different addresses and are set to the “middle” mode.

  • Bus used to connect the sensors: IT bus, Industrial Bus
  • Total bus length: 1000m + 9x 10m
  • Maximum number of sensors: 40
  • Sensors used:
    • 6x Temp-1Wire 10m
    • 2x Humid-1Wire 3m
    • 1x Temp-485
  • Accessories used:
    • 2x Poseidon Spider
    • 2x RJ45 Patch cable 300m (RJ45-RJ45)
    • 1x RJ45 TP cable 300m (RJ45-4 pins, “LAST” wiring)

Conclusion:

This solution is not limited by the IT Bus length. The Spider units can be up to 1000m apart. The solution is suitable for large-scale applications with many sensors (e.g. server rooms).

 

Topology 4: Using the Industrial Bus – star topology

This solution demonstrates a star-like connection of sensors to the Industrial Bus using an S-Hub unit. The S-Hub is the central point that connects individual sensors. The maximum bus length decreases to 500m because the cable length of all sensors connected to the S-Hub must be counted twice. A Temp-485 sensor with termination is at the end of the bus.

  • One Temp-1Wire temperature sensor with a 10m cable is connected directly to the Poseidon unit, to the RJ12 jack.
  • The Industrial Bus connects to the S-Hub input via a RJ45 patch cable. At the same time, the cable powers the sensors as well as the S-Hub; extra power can be supplied by an external power adapter.
    • Sensors must be connected to the S-Hub in a sequence, starting from output No. 1. Outputs cannot be skipped. (For instance, connecting outputs 1,2,5,6 while leaving outputs 3 and 4 unconnected will not work.)
  • First three temperature (Temp-485) and temperature/humidity (HTemp-485) sensors are connected in sequence to the first three outputs. An RJ45 / 6-wire cable, wired according to the “MIDDLE” version, is used to connect them.
  • The Spider unit is connected with a Patch cord. The Spider connects four Temp-1Wire sensors at 4x 10m distances. The Spider unit is in the “MIDDLE” mode.
  • The Industrial Bus is terminated at the Temp-485 sensor connected to the S-Hub at position No. 5. The connecting cable is wired according to the “LAST” version, termination is enabled at the sensor (Term=On).

Topology 5: Using the Industrial Bus – daisy chain

The solution demonstrates daisy-chain linked sensors on the Industrial Bus. Note the distances between sensors. The Spider unit connects four local temperature sensors. At the end of the bus, there is a Sens-UI voltage and current sensor with termination enabled.

  • One Temp-1Wire temperature sensor with a 10m cable is connected directly to the Poseidon unit to the RJ12 jack.
  • Two HTemp-485 temperature/humidity sensors are connected at the beginning of the bus, using a 4-wire cable connected to the terminals.
  • The bus continues to the Temp-485 temperature sensor, still with 4 conductors.
  • The Temp-485-Pt100-Cable uses a 4-wire connection as well. The temperature is measured by a Pt100 sensor mounted on a 2m silicon cable.
  • The next Temp-485-Pt100-2xDIN converter, mounted on a DIN rail, uses a 4-wire connection. Two external Pt100 thermometers measure two temperature values.
  • The following Temp-485-Pt100-Box sensor, designed for external environment, includes a probe for precise temperature measurement. 4-wire connection.
  • The Spider unit is, on the contrary, connected via a RJ45 jack. The Spider connects four Temp-1Wire sensors located 4x 10m away.
  • Please note the crossing of cables. It is necessary to respect the input and output designation of the RJ45 jacks. The Spider is in the “middle” mode.
  • The Industrial Bus finally leads, via a 4-wire connection, to a Sens-UI sensor that measures external voltage and current.
  • At this point, the bus is terminated by an external 120 Ohm resistor between the A and B pins.

     

 

Related products and links


Temp-485 HTemp-485 Temp-1Wire Door Contact Poseidon 1250 Poseidon S-Hub Poseidon Spider