Tutorial expert 1:
Build a Radio Network
Content of the tutorial:
Dear user, if you are reading this tutorial it is supposed that you have read and understood all the previous ones. So it's time to learn more about Devise Home and its cool features.
In this tutorial we'll start learning about how build a Radio Network inside your home. But first of all, why do we need of a Radio Network?
Actually a Radio Network is not strictly necessary: you can buy a controller that has lots of digital and analog pins and connect any of your devices, sensors, relays etc through small cables
But let's try to think about what happens if your devices are located everywhere inside your home. You should spread cables all around your home, and that is a very annoying way to build your controlled system.
The very convenient and clean alternative is to put a controller board in any of your rooms, or wherever it is needed, and connect all the controller boards together through a Radio Network.
In this way you can have of course the advantage of a simpler and clean installation. However this solution is also less expensive, because the cost of a controller board and a radio device is not so high than meters and meters of cables.
A Radio device is a piece of hardware, i.e. a small board, that allows a control board to transit/receive through as radio signal digital data to/from other control boards.
There are more kinds of radio devices that Devise Home can handle:
- Bidirectional 2.4Ghz Transceiver;
- Unidirectional 433Mhz Transmitter/Receiver (for European standard);
- Unidirectional 315Mhz Transmitter/Receiver (for American standard);
- XBee (not implemented yet, it will come soon);
Any of these devices have different features and is up to the user to choose the more suitable for the project. For more information about these devices please refer to Radio Device section in Devise Home User Manual.
In this section we can see how to use a radio device. The example we're going to explain is very simple: how to switch on for one second a led (or any other devices) connected to a control board, by pushing on a button connected to another control board.
In this project you can find the two control boards, a push button, a led, a connection service, a timer and two radio devices. As you can see the project is very simple and composed by elements that you have already met in previous tutorials. Only the radio devices are new.
Let's now see how to connect the two modules through those radio devices. First of all we have to choose what kind of radio device pick from the tools pane: we have two options:
This device is called radio24 because it transmits at a frequency of 2.4Ghz. It is a bidirectional communication device, so it is very useful when you need an answer/feedback from the controlled module (we will see this subject in next tutorials).
It operates at 433Mhz or 315MHz (the former for Euroean users, the ladder for American users, for other countries please check what frequency is legal). In this case you need a pair of tx and rx devices, called radioTx and radioRx, set of course to the same frequency. In this case there is no feedback from the controlled module, so, if you need it, this shouldn't be the preferred choice. However you can have the advantage of using this kind of radio device when you need to control lots of target devices all together, having one tx and more rx devices, as for example when you need to selectively switch on/off some or all the lights in your wide garden.
Well, once you have chosen the right radio devices and attached them to the two modules in your project, you can connect each other them by clicking on one of the radio devices with the right button of your mouse and select the 'connect' item. The other radio device will now be highlighted and you can click on it to make the connection.
That's it! And from now on any operations to complete your project are well-known: nothing more than what we have already seen in previous tutorials.
As usual, if you want to learn more about radio devices please refer to Radio Device section in Devise Home User Manual
The hardware realization of this project is very simple and can be done following the schematic diagrams provided by our Devise Home Skema tool . Of course there will be two connection schematic pages, one for each control modules.
The only recommendation is about the distance between the two radio devices. Of course it can not be so high, due to the small power of radio signal. However, in case of radio24 device, you can increase the max working distance by using devices with external (and not embedded) antenna.
If you are using unidirectional devices, both the tx and the rx device are not provided of antennas. So in this case you need to buy or, better, build one. It is very simple: take a straight piece of cable of exactly 17cm length for 433Mhz or 24cm length for 315Mhz and it will be a good antenna.
Lastly, if you want to learn more about building an antenna, please try this link: http://forum.arduino.cc/index.php?topic=181977.0.