Instructables
Picture of Back home
What does it do? It tweets when you arrive at home, along with an Adafruit Engineering Quote.
Where is the Twitter account? Here  (note that for privacy reasons, this account isn't actually precise).
Is it cheap? Yes indeed, it only requires an arduino board, an rfid reader and a rfid keychain. It should be under 40$.
How does it connect to the Internet? The computer runs a Python script that relays the serial data sent from the Arduino to Twitter.

How does it work? The Arduino is connected to the RFID reader, when an RFID tag is detected, the arduino writes to the serial : "I'm back home" followed by one of the engineering quotes. Each time this happens, an integer is incremented in order to change which quote is published each time. The serial data is transmitted to the computer through the USB cable and is then read by a simple Python script.
The script takes the serial data, and 'tweets it' (not sure if tweeting is a valid verb).

What is Python?   Python is a relatively simple high-level programming language, it is clear, powerful and easy to learn.
Chances are, it's already installed on your computer. 

What do I need? You don't need to have exactly the same things as me. Any Arduino compatible board will work, you can use another RFID reader (make sure your keychain matches the protocol that can be read by your reader).

-an Arduino  board
-an RFID reader (here an ID-20 )
-an RFID tag 


Step 1: Hardware

The hardware is simple, you only need to connect your RFID reader to your Arduino.
For the Innovations ID-20:

pin 2,11 ------------------ 5V Arduino
pin 1,7 -------------------- GND Arduino
pin 9 ----------------------- Digital 6 Arduino


There really isn't anymore to it.
 
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fwanderwrwr3 years ago
So, with this nice device now we are able to know when you're getting home and then after a few tweets, imagine, without too much effort, when your are getting out! So come on thieves, my house is emptyyy..!
Ok, this is a great project, but I'm always scared by this too invasive technologies! ;)
paasselin (author)  fwanderwrwr3 years ago
That is true. Although you could adapt this for more private communication. Send a text to someone when you get home.
Then again, I don't use this so...