I have a couple of RFDuinos (Small Arduinos with built in BLE - Specs here) which I want to connect with sensors and place around my yard. My thinking was to have all these separate rfduinos connect to some type of wireless gateway (Arduino Uno?) via bluetooth, which the gateway would receive, and using wifi, would then upload that data to the cloud.
What's the best approach for what I'm trying to do without it being too costly. I currently have 2 rfduinos, and an arduino uno. Should I purchase a wifi shield, or is there a cheap arduino that I can purchase with wifi and bluetooth capabilities? How have others tackled this?
Using bluetooth like that isn't such a good idea but, since you have the RFduinos already, you could do something like
Get a BLE master for the Uno and set it up to poll and converse both with the RFDuinos. This involves some pretty smart work running the BLE in AT mode, but it is a pretty cheap investment.
Once you have succeeded at that, get a WiFi shield or, in my view preferably, an ethernet shield and a WiFi repeater, for the Uno. Either way you now have a Uno able to act as a base station between the RFDuinos via bluetooth and the world via WiFi. The Uno can even run its own sensors as well.
You can then send the data to the Internet of Things like Xively and access it with your phone wile you are sitting on the beach in Acapulco.
You might find the Phillipe Cantin blog useful for the bluetooth.
I'll definitely look into your suggestions! You've got me thinking though, for future projects, what would be the recommended way of connecting sensors to a base station, if not via bluetooth?
There are a number of little transceivers that are better suited for Arduinos to talk amongst themselves, but I'm not familiar with them. The NRF24 has about the same cost and range as bluetooth. Bluetooth is better employed to talk to the outside world, like your phone. Using bluetooth as a LAN is not impossible, and cheap enough to try out with the gear you have.
I'm doing something somewhat similar in making a weather station.
I'm using 3 Jeenodes. Two are outside collecting data from sensors and one is inside connected to an LCD screen.
The inside Jeenode is also connected via 12C to a Yun which saves the data and serves up a web page.
The Ethernet shield is ideal and about the same as mine. Note that it has an SD card slot.
The HC-05 would be fine and the price is right, but I note that your other devices are BLE, and the HC-05 is not. I understand this means that your BLE devices will be forced to operate in bluetooth v2. There are other devices that are BLE like the Tinysine, which are only marginally more expensive. BLE offers more range than the HC-05 and you might as well take advantage of that.
I use a multi function wireless mini router. It is distinguished by having two RJ45 sockets. I have seen them for $15 lately.
A Bluetooth LE has about 100m range, is about the size of a postage stamp, weighs about the same, and consumes very little power. This all sounds pretty good for an r/c plane, and I imagine the range could be extended with an additional antenna.
Data is data, and it doesn't matter if it comes from an r/c plane or from something stuck in a tree like in the above picture.