Hey guys i'm doing a home automation project. I want several 'slaves' connected to the 'master'. The data will be sent in both direction(from slave to master and from master to slave). What type of wireless module should i use for this purpose? I think that the Xbee and nrf24l01 will be perfect for this purpose but which one should i use? What are the advantages and disadvantages of each? Thanks 
Hi,
There is a Home Automation section in this forum, you may find more info there..
Tom..
I would not even look at the XBee. It is too expensive.
I found your plans and the nrf24l01 will be super duper perfect for them.
If you're trying to build "slaves" like [u]this[/u]*, I'd recommend against building them yourself. There are quite a few engineering & construction "challenges".
You can build your own controller (master), but I'd recommend that you choose one of the existing home automation protocols so you don't have to build the modules (slaves) and so you can easily expand your system without re-engineering it.
....I've had a combination X-10/Insteon system for many years. I've got about 8 remote switch/dimmerses & controlled devices, a master timer-controller, and a few of plug-in & wireless remote controllers. I didn't build any of it myself, but I did build a "sunrise dimmer" that plugs-into a X-10 controlled outlet. The time-of-day turn-on is handled by the X-10 system and the dim-up is handled by the circuit I built.
- X-10 is not bi-directional, but there are other (more expensive) protocols that are bi-directional.
I would use openHAB to get all the support and the ability to integrated with other products.
Have a look at these links which includes some projects with details:
https://sourceforge.net/projects/homegenie/
https://github.com/abouillot/HomeAutomation/blob/master/Gateway/Gateway.ino
--- bill
If you decide to use wireless transceivers have a look at the Hope Electronics RFM22B. It's a 413 MHz. transceiver with up to 100 mw. transmit power, and very high receiver sensitivity. They're a couple bucks apiece on EBay, and the RadioHead Library for them is the best documented library I've ever used. I have a growing home automation system using these, and all they ever do is work right.
There half the size of a postage stamp, so they nestle down very nicely on a circuit board.
Don't forget to check RFM69 as well, apart from an excellent radio transceiver it offers features like CRC, variable payload size and AES encryption.
Cheers