Daisy Chaining Capabilities of Sensors

2 Minute Read

| Overview

Not all parts of a room experience similar conditions, we at Carrier truly believe in that. Hence, to monitor the conditions of a room, providing the necessary conditioning monitoring with only one sensor is not sufficient.

To tackle the problem Carrier introduced a portfolio of sensors that can be mounted at different parts of the room.

The Room controllers/ master devices, SmartNode, HyperStat and HyperStat Split were provided with just one port to accommodate just one sensor, apart from the onboard ones (as applicable).

This led to bringing in the daisy-chaining capabilities in all the latest sensor releases, and a wiring harness to support the daisy-chaining of the sensors in a bus network.

| Wiring Harness for Daisy Chaining

This wiring harness comprises a 3-wire female connector at one end, and two male connectors at the other end. This can be plugged into the daisy chain ports provided in the sensors for power and communication.

Daisy Chaining of sensors is achieved, when the above wiring harness is combined with the 3 Pin to 3 Pin cable of lengths 18 inches, 20, 30, and 50 feet.

| Daisy Chaining Rules

Below are the rules to be followed while daisy-chaining sensors in a bus:

• A maximum of 4 one wire interface devices can be connected in a bus
• A maximum of 4 multi sensors can be supported in a bus 
• A maximum of 3 duct sensors can be supported in a bus.
• A maximum of 1 differential pressure can be supported in a bus.
• A maximum of 1 device of Ceiling or Flush or Wall sensor can be supported in a bus.

| Examples

Below is an illustration of the daisy chaining example for the Multi-Sensor

Daisy Chaining Multi-Sensor 

When Daisy Chained

• Not more than 4 multi sensors can be daisy chained in a Bus.
• The Temperature, CO2, and Humidity values of the sensors in the bus are averaged for the master device.
• The occupancy in the master device results, when at least one Multi Sensor in the bus detects occupancy.

 

Daisy Chaining Multi & Wall Sensor

When Daisy Chained

• No more than one wall sensor can be on the  sensor bus due to the absence of an address setting mechanism.
• The Temperature and Humidity values of the sensors in the bus are averaged for the master device

| Address Assigning Strategy

When more than one sensor is used in a bus, each sensor takes up an address for it. The address taken up by sensors would differ based on the types of sensors used in the bus.

The Multi-sensor and the Duct sensor in the family, with address setting switches, can be used to set the addresses for when more than one such sensor is used in the bus.

The other sensors in the family, the Wall, Ceiling, Flush, and Differential pressure sensors, do not come with an address setting switch. When these are used in the bus, they take up the address "0", allowing the other sensors in the bus to take up the other addresses (not more than one of these sensors can be used in the bus, and they are usually the last in the bus).

Below are a few examples to better illustrate the addressing assigning strategy:

Example 1

Sensors	Sensors in the Bus
	Wall Sensor	Duct Sensor	Multi Sensor	Multi Sensor
Address Range	0 (fixed)	0,1 or 2	0,1,2 or 3	0,1,2 or 3
Address Used	0 (fixed)	1	2	3

 

Example 2

Sensors	Sensors in the Bus
	Ceiling or Flush Sensor	Duct Sensor 1	Duct Sensor 2	Multi Sensor
Address Range	0 (fixed)	0,1 or 2	0,1 or 2	0,1,2 or 3
Address Used	0 (fixed)	1	2	3

 

Example 3

Sensors	Sensors in the Bus
	DPS	Duct Sensor 1	Duct Sensor 2	Multi Sensor
Address Range	0 (fixed)	0,1 or 2	0,1 or 2	0,1,2 or 3
Address Used	0 (fixed)	1	2	3

 

Example 4

Sensors	Sensors in the Bus
	Multi Sensor 1	Multi Sensor 2	Multi Sensor 3	Multi Sensor 4
Address Range	0,1,2 or 3	0,1,2 or 3	0,1,2 or 3	0,1,2 or 3
Address Used	0	1	2	3