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Concept

Concept


Products: RP-C, SpaceLogic Sensors
Functionalities: Hardware
Product version: 3.2
9/1/2020

RP-C Sensor Bus

The RP-C sensor bus allows SmartX Sensors to be connected to the controller.

The sensor bus is a proprietary RS-485 bus, which provides both 24 VDC power supply and communications for the sensors.

The maximum total length of the sensor bus is 61 m (200 ft). The sensor bus uses a Cat 5 (or higher) unshielded, straight-through wired cable with eight conductors (four twisted pairs) and RJ45 connectors. The wire size (cross-sectional area) should be 22 to 26 AWG (0.34 to 0.14 mm²). When the RP-C controller is installed in a space that handles conditioned air or return air, the sensor bus cables and IP network cables frequently must be plenum-rated to meet applicable building codes. For more information, see Wiring .

Notice

LOSS OF COMMUNICATION

  • Ensure that the total length of the sensor bus does not exceed 61 m (200 ft).

  • Use a Cat 5 or higher unshielded twisted pair cable with eight conductors (four twisted pairs), a cross-sectional area of 22 to 26 AWG (0.34 to 0.14 mm 2 ), and a rating that meets the requirements of the target environment.

Failure to follow these instructions can result in loss of communication.

By default, the RP-C controller's Sensor Bus port (RS-485 Com A) is configured and allocated for the sensor bus. For more information, see RP-C Communication Ports .

 
action_zoom_plus_stroke Location of the Sensor Bus port (RS-485 Com A) on the RP-C controllers
Figure: Location of the Sensor Bus port (RS-485 Com A) on the RP-C controllers

You can connect a single SmartX Sensor to the sensor bus, or you can connect two to four SmartX Sensors in a daisy-chain configuration.

Note:

When connecting SmartX Sensors to the sensor bus through a daisy-chain configuration, it does not matter if the incoming and outgoing cables are connected to one or the other sensor bus port on the SmartX Sensor.

The maximum number of SmartX Sensors that can be connected to the sensor bus is variable depending on the power consumption for the selected SmartX Sensor model and the combination of cover and sensor base type.

When calculating the power consumption to validate your sensor bus configuration, ensure that you add the power consumption (mW) for all SmartX Sensor models, sensor bases, and covers used on the sensor bus to determine the total power consumption. The sensor bus can supply maximum 2000 mW. SmartX Sensor combinations totalling more than 2000 mW are not supported. The following table can be used for calculating the total power consumption.

Description

Model Number

Power (mW)

Sensor base with temperature sensor

SXWSBTXXXSXX

90

Sensor base with temperature and humidity sensors

SXWSBTHXXSXX

90

Sensor base with temperature and CO 2 sensors

SXWSBTXCXSXX

490

Sensor base with temperature, humidity, and CO 2 sensors

SXWSBTHCXSXX

490

Blank cover

SXWSCBXSELXn a

0

Blank cover with occupancy sensor

SXWSCBPSELXn a

20

3-button cover (buttons for override and setpoint control)

SXWSC3XSELXn a

190

3-button cover (buttons for override and setpoint control) with occupancy sensor

SXWSC3PSELXn a

210

Touchscreen display cover

SXWSCDXSELXn a

190

Touchscreen display cover with occupancy sensor

SXWSCDPSELXn a

210

Touchscreen display cover with light control buttons

SXWSC2XSELXn a

190

Touchscreen display cover with light control buttons and occupancy sensor

SXWSC2PSELXn a

210

Touchscreen display cover with light and blind control buttons

SXWSC4XSELXn a

190

Touchscreen display cover with light and blind control buttons and occupancy sensor

SXWSC4PSELXn a

210

Complete SmartX Sensor model with temperature sensor, buttons for override and setpoint control, and LCD display cover

SXWSATXXXSLn a

80

Complete non-communicating b SmartX Sensor model with resistive temperature sensor (10 kohm type 3 thermistor) and blank cover

SLAnXXX c

SXWSATXXXRXX d

0

eCommission Bluetooth Adapter e

SXWBTAECXX10001

300

  1. The last character (“n”) of this model number indicates the housing: X (Medium matte white), W (Optimum glass white), or B (Optimum glass black).
  2. The SmartX resistive temperature sensor is not designed to be connected to the sensor bus, but instead is connected to I/O points/terminals on the SmartX IP controller using a two-wire connection.
  3. The fourth character (“n”) of this model number indicates the housing: S (Medium matte white), W (Optimum glass white), or B (Optimum glass black).
  4. The model number SXWSATXXXRXX is replaced by SLASXXX.
  5. Connect the eCommission Bluetooth Adapter to the SmartX Sensor for temporary commissioning and servicing only.

To summarize the power conditions, the sensor bus supports the following key SmartX Sensor combinations:

  • Blank covers: Up to four sensors of any combination of sensor base types

  • 3-button and touchscreen covers:

    • Up to two sensor bases with CO 2 option

    • Up to four sensor bases without CO 2 option

  • SmartX LCD temperature sensors: Up to four sensors are supported

 
action_zoom_plus_stroke Examples with one SmartX Sensor and four SmartX Sensors connected to an RP-C controller in a daisy-chain configuration
Figure: Examples with one SmartX Sensor and four SmartX Sensors connected to an RP-C controller in a daisy-chain configuration

Each SmartX Sensor has two 2-position DIP switches, which are used to give the sensor a unique address on the sensor bus. An incorrectly configured or improper DIP switch can cause two sensors to have the same address on the sensor bus, which means that both sensors will be offline. For more information, see SmartX Sensors .

Notice

LOSS OF COMMUNICATION

Ensure that the address DIP switches on the SmartX Sensor are configured to give the sensor a unique address on the sensor bus.

Failure to follow these instructions can result in loss of communication.

Note:

SmartX Sensors connected to the sensor bus through a daisy-chain configuration can be assigned addresses regardless of the order in which the sensors appear in the daisy chain. For example, sensor number 1 can have the address 6, sensor number 2 can have the address 4, and so on.

See Also

  • Hardware Overview
  • RP-Cs
  • Wiring
  • RP-C Communication Ports
  • Connecting SmartX Sensors to an RP-C Controller
  • RP-C
  • SmartX Sensors