ATtiny85 mailbox sensor

The postman always rings twice. Well, in my world he doesn't ring at all. That's why I created this little device that tells me when the postman has delivered my snail mail. I would like this device to be small enough to fasten in the mailbox lid (in Norway most outside mail boxes have a top lid that swings upwards).

How it works

The device don't use any power at all when not in use. That's what I call the ultimate low power device. I have tried several ways to implement this, including a LDR to trigger when light enters the mail box. I ended up with a small device that fits in a tic tac box. The trigger is a simple tilt switch that turns the curcuit on when the lid is opened.

That again will run the ATtiny85s program that send a signal to my RFXCOM RFXtrx433E USB 433.92MHz Transceiver using the X10 protocol. Domotiga will then pick up the signal and process it. In my case, a push message is pushed to my mobile phone and tell me that the lid was opened.

Parts:

1 x ATtiny85 (I use a V-PU10, the low power version that can run down to 1.8V) 
1 x STX88 433MHz transmitter w/antenna
1 x CR2032 coin cell 3V lithium battery (or any other 3V source)
1 x small tilt switch
1 x 3mm LED (optional)
1 x 270R resistor (optional)
1 x box (I use a Tic Tac box)

The code (may change without notice):

 

 

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