Have you caught yourself checking mailbox several times before mailman comes? I don’t call this a problem, but when mailbox is out of sight it takes your time. So Robert decided to modernizer mailbox so it would send notification once mail arrives. In his mail box he added moteino – custom wireless Arduino which simply reads hall sensor. When mailman puts something in the box, he opens it and thus magnet activates the sensor.
Moteino message can be processed in many ways. For instance computer running python script can simply send email or SMS notification. Since Moteino is battery powered a special care is taken to save energy. There is a transistor key used to control power for hall sensor. Device is kept most time in sleep and woken every 250ms averaging power consumption of about 60uA. This is cool way to convert snail mail in to email, isn’t it?