Daisy Chaining Capabilities of Sensors

2 Minute Read

| Overview

Not all parts of a room experience similar conditions, we at 75F 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 75F introduced a portfolio of sensors that can be mounted at different parts of the room, but the problem ended there.

The Room controllers/ master devices, SmartNode, SmartStat, and HyperStat 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-Pin 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/Flush/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

• Not more than a wall sensor can be daisy chained in the 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 a few sensors are 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 RTH/ 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).

One of the same type of sensor can be used with the same address .. Like 2 x wall sensors or 1 x wall sensor and 1 x Ceiling

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

Example 1

Sensors	Sensors in the Bus
	Multi Sensor 1	Multi Sensor 2	Duct Sensor	Wall Sensor/RTH
Possible Addresses	0,1,2,3	0,1,2,3	0,1,2	NA
Address Taken Up	2/3	2/3	1	0

 

Example 2

Sensors	Sensors in the Bus
	Multi Sensor	Duct Sensor 1	Duct Sensor 2	Ceiling/Flush Sensor
Possible Addresses	0,1,2,3	0,1,2	0,1,2	NA
Address Taken Up	3	1/2	1/2	0

 

Example 3

Sensors	Sensors in the Bus
	Multi Sensor	Duct Sensor 1	Duct Sensor 2	DPS
Possible Addresses	0,1,2,3	0,1,2	0,1,2	NA
Address Taken Up	2/3	0/1	0/1	0

Example 4

Sensors	Sensors in the Bus
	Multi Sensor 1	Multi Sensor 2	Multi Sensor 3	Multi Sensor 4
Possible Addresses	0,1,2,3	0,1,2,3	0,1,2,3	0,1,2,3
Address Taken Up	0/1/2/3	0/1/2/3	0/1/2/3	0/1/2/3

 

| Daisy Chain Guidelines

Based on the observations made on various testing and commissioned environments, conclusions are drawn as guidelines for daisy chaining different sensors with different edge devices.

For the best optimal results from the setup, users must adhere to these practices.

Multi Sensors Daisy Chained

The Below table talks about the distance at which different Multi-sensors should be, while in a daisy-chained setup, with different edge devices using the 3 Pin to 3 Pin cable of different length combinations.

Device	Distance(ft)
	1-MS	2-MS	3-MS	4-MS
HyperStat	190 to 300	190 to 300	100 to 160	60 to 80
SmartNode	120 to 300	120 to 300	100	60 to 80
HelioNode	190 to 300	190 to 300	100 to 160	60 to 80

 

The above figure depicts one such wiring guideline with distances to be maintained between the multi sensors, daisy chained with different edge devices

i.e.

When Multi Sensors are daisy chained with HyperStat:

• Four multi sensors can be wired within 100 feet distance.
• Above 100 feet and below 200 feet distance only three multi sensors can be wired and the last sensor should be within the 100 feet distance.
• Above 200 feet and below 300 feet distance only 2 multi sensors can be wired and the last two sensors can be within 100 feet or 200 feet.

When Multi Sensors are daisy chained with SmartNode:

• Four multi sensors can be wired within 100 feet distance.
• Above 100 feet and below 200 feet distance only two multi sensors can be wired and the last two sensors should be within the 100 feet distance.
• Above 200 feet and below 300 feet distance only 2 multi sensors can be wired and the last two sensors can be within 100 feet or 200 feet.

Different Sensors Daisy Chained

The concept of maintaining a particular distance between the sensors not only applies to the multi sensor but also to other sensors that can be a part of the daisy chain.

The following are the other sensor types that can be combined in a daisy chain:

MS - Multi Sensor

RTH - Wall Sensor

DTH - Duct Sensor

DPS - Differential Pressure Sensor

The below table talks about the distance at which different sensor types should be, while in a daisy-chained setup, with HyperStat/ Smartnode/ HelioNode using the 3 Pin to 3 Pin cable of different length combinations.

Device	Distance	Sensor Combination	Remarks
HyperStat/ SmartNode Helionode	200 Feet end (The last sensor is at 200 feet, other consecutive sensors are 20 feet away last one in the bus)	RTH-MS-DPS-MS	DPS does not get detected by the SmartNode & Helio Node in the bus,
		RTH-MS-DPS
		DTH-MS-DPS
		DTH-RTH-DPS
		DPS-MS-DTH-RTH
		DPS-MS-DTH-MS	DTH firmware resets every 4 seconds. When connected with Hyperstat, SmartNode & HelioNode. Can be visualized in the backend application, but no signal on the device
		DTH-MS-RTH-MS
		DTH-MS-DPS-RTH	DPS does not get detected by the SmartNode in the bus DPS does not get detected by the Helionode in the bus, if DTH is at the beginning of the daisy chain

 

Device	Distance	Sensor Combination	Remarks
HyperStat/ SmartNode Helionode	200 feet Total(40-100-160-200) (The first sensor is at 40 feet, the second at 110 feet, the third at 160 feet, and the fourth at 200 feet)	MS-RTH-MS-DTH
		DPS-MS-DTH-MS	DTH firmware resets every 4 seconds when connected with HelioNode. Can be visualized in the backend application, but no signal on the device
		DPS-MS-DTH-RTH