Electronic – arduino rf communication: beginner

arduinohome-automationreceiverRFtransmitter

I would like to implement a home-automation system on my arduino.
For this project I would like to communicate with the different devices by radio frequency.
So that would be different 433 mhz receivers and one 433 mhz transmitters.

Now my questions:

  1. How can the transmitter differentiate the signals of the indiviual devices. Do they each have an unique id or such? Or do i need some other part or controller to identify them?

  2. What is the purpose of a transmitter encoder?

I'm rather new with electronics and arduino so any comment or suggestion is appreciated.

Best Answer

As you describe it, with one way communication from a single master to many "slaves", the task is very easy.

The master simply sends messages of the form Address + Data. All slaves hear all messages and each slave checks for message with its own address and actions them while ignoring the rest. As the master has complete control of the transmitting this can make very efficient use of the channel capacity (when efficiency is needed).

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If you want to go the other way and have many "outposts" sending messages to a single central location in response to messages from the Master (usually on a channel of its own) "the fun begins". Out of such a need has risen much of the data comms protocols that we see today, and the internet.

The (or a) classic early initiator was named "Aloha Net" ("Hello Net") operated by the University of Hawaii to outposts around the islands. This used the simple method of an outpost "just sending a message when it had one". If it did not get an acknowledgement within a certain randomly set time it would send it again. This allowed for radio fade and noise and collisions with other messages. This works well when the total message transmit time is a small percentage of the tome available and when message lengths are short compared to time between messages. This would often apply to home automation applications, allowing an easy two way communications protocol when you find you need or want two way commiunications - as you soon will :-).