So What Is Z-Wave ?
Having an interest in all things to do with gadgets and home automation, you soon get caught up in the weird and wonderful terms and technologies that are bounced around, which can be anything from your Apples to your Zigbees.
One of the terms I always liked was Z-Wave, I guess because it felt more nostalgic like x-rays, plus unlike many of the other Home Automation technologies out there, it felt within reach due to it’s pricing.. So with that in mind, i had to ask myself. “What is Z-Wave?”
Well Z-Wave is a protocol for wireless communication between electronic devices and it’s main characteristic are as follows:
* Primarily intended for automation,
* Relatively secure,
* Two-way (each component is both receiver and transmitter)
* Utilises a mesh network
As Z-Wave uses radio frequencies to establish communications it therefore allows two electronic components using the Z-Wave protocol to discuss together and exchange information. This information can be data things like a temperature reading …or orders (turn … ON or OFF) or it status (“I’m on, or I’ve been tripped …”) etc …
Like any wireless RF signal, the signal range of a Z-Wave is strongly influenced by the environment in which it resides, for example walls will impede its progress through the air. Therefore you should assume that the signal within a normal house/flat will only have a range of 30 meters, whereas outdoors you could expect up to 100 metres.
As an example, lets say you’ve moved into a house with two Z-Wave components, such as a wall socket and a motion sensor. During the implementation, the two elements need to be paired and networked. The resulting network uses a grid system, that allow us to add a second wall socket, which can be at a distance outside the range or one, but inside the range of the other, allowing it can still be controlled!
No magic in this. The order is on or off from the remote control to the first outlet controlled that relays the order to the second outlet. The signal will thus “hop” from one element to the other in order to reach its intended destination. In addition, this feature, called a mesh, allows your network architecture not to be defined in advance, but instead you build it gradually as you add more z-wave devices.
Modules in the network are called nodes and each node has the ability to act independently or in partnership with other nodes on the network. Such nodes can be connected to the mains (230V) or run off just battery power. The draw back of using battery devices is that they’re not always on, (in order to save power) so while they can act as a signal relay, its best to leave this task to those nodes connected to the mains as the best nodes to transfer any signal are those that are the most attentive to any signals that need to be relayed.
A Z-Wave network can have up to 232 nodes, which should be fine for a conventional house. However if you did want more, then you would just simply set up a second network, with its own controller and then establish a bridge between the two networks.
So as you’re hearing, it’s a lot like a basic computer network, each module/node is recognized on the Z-Wave network by a unique code, which is assigned to it by the controller that it’s associated with. This, by design allows multiple Z-Wave networks to coexist together without interfering. However In order to achieve this level of harmony, a certain level of discipline is required whenever you i) add (include), ii) delete (exclude) or iii) simply move a node in your network, and that’s why you need to have a z-wave controller to manage all your components.
When you add (include) a node, it’s important that the controller confirms that it’s received the new node’s information, allocated it an ID and has then positioned it on the Z-Wave network. Hence when you want to remove one it’s important to follow the correct procedure instead of just unplugging and removing it. In addition to this, as the network is optimized for the signal to follow via the shortest route to reach its goal, it will aim to use other node(s) in its path to get there.
In the event that you do want to move a node within the same network, it’s sometimes recommended that you delete (exclude) it first and then (re)include it again once it’s in its new location. Advances however in the design and intelligence of some of the controllers nowadays allow you to simple relocate it and then update (heal) the network in order for it to accommodate the change.
Each node is built to act as a transmitter and receiver, which means it’s able to both send or receive information such as: battery status, a temperature value or the operating status (ie on or off), etc … All of which enables the controller to determine the state of each node as well as request specific information or for an action to be carried out. Also, within the communication protocol the node or controller that’s receiving the information, will send an acknowledgement of receipt to the sender
Before starting to transmit a message, it listens to the current traffic in order not to collide on the network with another message. So if there is no traffic at that time, it can be issued immediately, otherwise it acts like a car that wants to enter onto a motorway: by using the acceleration lane to allow it to fit into the flowing traffics with crashing into anything.
For the technical amongst you, the modulation signal used is FSK (frequency-shift keying).
So.. What’s My Frequency Kenneth?
Depending on the country you live in, the signal frequency used by the Z-Wave is not consistent, therefore you will need to keep that in mind should you ever be tempted to buy Z-Wave kit abroad.. See the frequency used per country below.
Australia 921.4 MHz
Brazil: 921.4 MHz
* CEPT: 868.4 MHz
China: 868.4 MHz
Hong Kong: 919.8 MHz
India: 865.2 MHz
Japan: 951-956 MHz
Malaysia: 868.1 MHz
New Zealand: 921.4 MHz
Russia: 869.0 MHz
Singapore: 868.4 MHz
South Africa: 868.4 MHz
UAE: 868.4 MHz
USA / Canada: 908.4 MHz
* CEPT European Conference of Postal and Telecommunications entity coordination between agencies Post and telecommunications European countries: Albania, Andorra, Austria, Azerbaijan, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia Cyprus, Denmark, Estonia, Finland, France, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Moldova, Monaco, Netherlands, Norway, Poland, Portugal, Czech Republic, former Yugoslav Republic of Macedonia, Romania, United Kingdom, Russian Federation, San Marino, Serbia and Montenegro, Slovakia, Slovenia, Sweden, Switzerland, Turkey, Ukraine and Vatican.
These frequencies are shared with cordless phones or other electronic devices everyday but it avoids the 2.4 GHz band is a bit dirty especially with Wi-Fi network signals
The Z-Wave protocol is designed to use a transfer speed of 9.6 k bits per second, which may seem small, but it’s sufficient enough for the message (which is only a few bytes) to arrive at its destination quickly. The bandwidth can be increased as the technology evolves to approx. 40 Kbps
Now let’s discuss the hardware
For a while the Z-Wave chip were manufactured by a single company, a Danish company Zensys (founded in 1999 and acquired in 2008 by the American company Sigma Designs ). Zensys who designed the Z-Wave protocol, produced chips for the entire global market. However to help ensure supply, Sigma Designs have now also been authorised to produce the chips. Sigma Designs were granted a license back in May 2011 for their production at the Japanese company Mitsumi.
An example chip includes:
* a receiver / transmitter RF
* a microprocessor
* 32kB flash memory containing the Z-Wave protocol, application to manage and certain characteristics of the network it’s on.
* system interfaces (analog and digital) in order to connect all electronics such as sensors or triggers
* 3DES engine to ensure the privacy and authentication
* Triac controller for drives
Aside from concerns over the interpretation of the standard by manufacturers that implement it into their devices, the Z-Wave allows you to communicate elements of different manufacturers. It is not, however, an open protocol, but a proprietary technology which is governed by a firm, Zensys, a group of professionals and the Z-Wave Alliance (founded in 2005).
Z-Wave technology is filling my home and I’m thoroughly enjoying the functionality and information I receive from it, learning a bit more about the technology itself helped me, and I hope it’s of interest to you too.
Source: Z-Wave.com , Micasaverde Forum, & Abavala
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