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NICEIC - Technical Article

Smart Devices

This article introduces the term ‘smart devices’ and identifies typical devices that are commonly used. The article also briefly describes two methods of connecting smart devices [wireless and wired], and describes how communication between them is achieved.

Introduction

This article is the first in a series of four that considers how smart devices can be used to provide the user or building occupants with an automated system of control over building functions such as lighting, heating, appliance control and security, in both domestic and non-domestic properties.
Brief outline of the content to be included in subsequent Connections articles:
Issue 214 Smart homes – how to create a smart home by showing how devices can be retrofitted into existing installations to provide control over lighting, heating, appliances and security systems.
Issue 215 Smart buildings [commercial/industrial] – how smart devices can be used to improve energy efficiency with consideration of paragraph 17.7 of Appendix 17 of BS 7671.
Issue 216 Measurement and recording of energy usage as given in recommendations 17.6 and 17.8 of Appendix 17.

What is a smart device?

A smart device differs from typical methods of control in that it can interact remotely with a user and/or other smart devices. Fig 1 shows a range of devices that are capable of being controlled by a handheld device and Table 1,whilst not exhaustive, identifies examples of sensors and controlled devices.

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Table 1 Commonly used sensors and controlled devices

Sensors

Controlled devices

Switches – binary, dimming and time

Lights, motors

Fire/CO detectors

Alarms, sprinklers

Thermostat

Boiler ignitor, pumps, radiator valves

Window and door detectors

Alarms

Motion – PIR, microwave

Lights, alarms

Video cameras

Lights, alarms, recording units, Smart plugs and socket-outlets

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Wireless system

Any of the sensors listed in Table 1 could be used for both domestic and non-domestic purposes. For domestic premises, smart devices would typically be connected to other devices and the network via a wireless network, as shown in Fig 2. This will be dealt with in more detail in Issue 214 of Connections. Not all wireless systems require a hub; some smart devices can connect directly to the router. However, this method may increase lag and reduce the speed of connection for other devices such as computers and TV streaming services. Where a hub is required, it is connected to the router using an Ethernet cable. Voice activated devices generally have an in-built hub so that they can be used with most smart devices from different manufacturers.

Wireless communication protocols

A wireless network will require communication between the smart devices and the router or the hub, where fitted. The common options are:

  • Bluetooth

  • Wi-Fi

  • Zigbee

  • Z-Wave

Bluetooth is a wireless technology that permits connection to devices such as computers, computer mice, keyboards, printers, mobile phones and hands-free headsets. It is typically used to transfer files, contact details, reminders and appointment dates between devices without the need for connecting wires.
Bluetooth has an indoor operating range of up to 10m, although this may increase to 100m with some types of device. Bluetooth generally operates within a frequency range of 2.400 and 2.483 GHz. Wi-Fi is a wireless technology that uses radio waves operating within the 2.4 GHz and 5 GHz frequency range to provide a local area network [LAN], allowing for the connectivity of devices and the transmission of data. A Wi-Fi network allows a PC, laptop, mobile phone or tablet device to connect at high speed to the internet without the need for a physical wired connection. However, the strength of the radio signals are relatively weak and generally cover short distances, although the typical range will be suffi cient to provide coverage throughout a typical home.
One wireless hub is usually enough to enable connection to the internet in any room in a home, though the signal will be strongest near the hub. The typical range of Wi-Fi is about 100m, although the range can be extended using a wireless access point [AP].

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Zigbee is an emerging standard that defines a set of communication protocols for low power digital radio signals. It has a typical application in areas such as home automation, telecommunication services and remote control. Smart devices operating with the ZigBee protocol installed are mainly for battery powered applications where low data rate, low cost and long battery life are the main requirements. The typical signal transmission range for ZigBee-based wireless devices is more than 100 m and operates in 868 MHz frequency bands. The number of devices [nodes] that can be connected, whilst large, would cause bandwidth problems if the number given in Table 2 was connected. For the connected devices to function properly, a controller or hub is required.
Z-wave is an RF [radio frequency] based wireless networking technology, primarily designed for smart home and office automation. It is another of the emerging technologies in the area of wireless home automation. As with Zigbee, Z-Wave operates using low-energy radio waves to communicate from device to device, creating a mesh network. The advantage of using a mesh system allows greater distances to be covered, in which the sent and received signals from the remote connected devices will use the most convenient communication route back to the hub. The number of smart devices that can be installed on a mesh is lower than that for Zigbee, but would still be sufficient for most homes. As with the Zigbee system, a controller or hub is required.

Table 2 Comparison of communication protocols

 

Bluetooth

Wi-Fi

Zigbee

Z-Wave

Frequency band

2.4 GHz

2.4 – 5 GHz

2.4 GHz

900 MHz

Power consumption

Medium

High

Very Low

Very Low

Range

10m / 100m

45m

10m

30m

Data rate [max]

1 MB/s

54 MB/s

40 – 350 kB/s

10 – 100 kB/s

Topology

Ad-hoc, very small networks

Point to hub, typically star

Ad-hoc peer to peer, star or mesh

Ad-hoc peer to peer, star or mesh

Max number of nodes

7

32

>65 000

232

Data type

Audio, graphics, Video, pictures, files

Audio, graphics, Video, pictures, files

Data packets2

Data packets

Advantages

Cost, easy to use

Data rate, flexibility

Reliability, performance, cost

Reliability, performance, cost

Application

Wireless connectivity between devices such as phones, PDA, laptops, printers, headsets

Wireless LAN connectivity, broadband internet access

Industrial control and monitoring, sensor networks, building automation, home control of smart devices, games

Smart home devices, security and office automation

Wired system

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For larger residential dwellings and commercial/industrial premises, a wired system using KNX technology would most likely be used, shown in Fig 4. This will be covered in more detail in a later issue of Connections.
KNX is a worldwide communication standard that defines interactions between devices on a network. It has a high level of interoperability, which means that a system can be built using different KNX products from different manufacturers that are still able to operate and communicate with each other. This permits a high degree of flexibility in the design and for additions and/or modifications of installations.

The smart devices for a KNX installation are connected by a two-wire bus [the most common form of installation], allowing them to exchange data. The cable used is often recommended by device manufacturers.
The function of the individual bus devices within KNX is determined by their project planning, which can be changed and adapted at any time. This will include, for example:

  • Sensors [wind, temperature, movement etc.]

  • Actuators [dimming units, electrical heating valves, displays]

  • System devices and components [Line/ Backbone-Couplers]3.

Sensors, as with the wireless system of Fig 2, are the starting point for every action because they gather information and send it on the bus as data packets. This can be information about room temperatures, movement, wind measurements or manually inputted instructions [push buttons]. Sensors are selected depending on the required application.
Actuators receive data packets, which are then converted into actions. This can include controlling blinds, dimming lights or controlling heating and air conditioning systems. Actuators are also selected depending on the required application, and consist of a bus coupler and an application module with the corresponding application program.
The application program is loaded into the devices connected on the bus, together with the project design and commissioning software. Such a connection is usually made with a PC connected via a USB or serial interface direct with the bus. The application program allows the software to recognise each separate device through an allocated address connected to the bus. The address maybe selected through a series of binary dip switches, selected during installation or through an allocated Media Access Control Address [MAC], which is preinstalled within the firmware of the device.

Summary

A smart device describes an electronic device, which can be a sensor or an actuator, that can be individually controlled or be connected to a network to interact with other smart devices.
The network may be wireless or wired but both types of arrangement provide enhanced automated control of a building’s services. Wireless protocols include Bluetooth, Zigbee, Wi-Fi and Z-Wave, to name a few. The use of a separate hub, whilst not always necessary, would reduce the loading on other internet connected devices.
The industry standard for wired networks is KNX, which has a high level of interoperability. Manufacturers often recommend Belden for the cabling used to interconnect the devices on a wired network, although other cable types with similar characteristics are not precluded.

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