Basic Idea This project puts a sensor into the mailbox down by the street. When the mailbox door is opened, it can send a signal to the home monitor (PC). If it can detect the presence of mail in the mailbox, then it could indicate when the mail has been removed, as well as indicate when new mail arrives. Just for fun, it could send an email to let you know that paper mail has arrived!

Block Diagram:

This is purely in the thought stages at this time, so I don't know what might appear here...

I/O Description:

• Ethernet to the mailbox. Probably only 10 Mb/s link, which frees the additional pairs to send low voltage A/C to power the remote unit, - or -
• Wireless RF transmitter. In this case, since there are no wires, we need a local power source. This could be a photocell, or perhaps a small generator that is activated when the mailbox door is opened and closed, - or -
• Cheap laser that sends an optical ping to the house where a small receiver is waiting. This makes it wireless, low power, and gives it great range.
• Sensor to detect the mailbox door, as in -, - or -
  • Magnet and either a reed relay or a hall effect. 
  • Optical, since it is usually daylight out when the mailbox opens and closes
  • Mechanical switch
• Sensor to detect mail
  • Optical beam hoping that the mail blocks the beam
  • Infrared, bouncing the beam off the usually white envelopes

Candidate Solutions:

Candidate solutions are presented in the order of most appealing, based on simplicity to implement and of course the cost of the implementation.

Wireless RF

A simple wireless transmitter, probably coded for noise rejection. The receiver can be in the house, and it could then relay the indication from the transmitter to the PC, and then to the network.

SitePlayer

SitePlayer has a couple of basic logic inputs that can be polled. This solution cannot send an email, unless the home PC is the device that initiates the mail after polling the SitePlayer.

Rabbit

Using a Rabbit, which is natively programmable, and has enough I/O, it should be simple enough. It could be polled as a web site (same as the SitePlayer), but the Rabbit reportedly can also send very very small emails using UDP transactions.

EtherNut

EtherNut could easily do this. Plenty of I/O. Can originate communications to the home PC and can send email, host a web server, and more.

TINI

TINI could easily do this. Plenty of I/O. Can originate communications to the home PC and can send email.