A physical mail sensor with 433 MHz radio transmission

Tired of having to get out of your filthy hole every day to see if mail has arrived? Want to finally catch that bastard that brings physical spam to your physical mail box in order to subject him to various force fields? Phyff is for you.

Just install the sensor in your mailbox, connect the receiver to the serial port of your Unix box, and filter the logfiles with something like swatch to trigger an audible beep.

I designed and built this thing as my first serious RF transmission project. Working on weekends and holidays and waiting for parts from Digikey, this took me about 2 months from mid-November 2005 to January 2006.

Technical specifications


The PCB of the detector/transmitter. The TLP434 module can be seen at the bottom left. This is a double-sided PCB. A big mess due to a bad soldering iron that burned some tracks. Double-side soldering can be difficult.



On the left, the IR transmitter LED with its reflector, and on the right, the IR receiver photodiode.

Receiver (hardware)


Screenshot of the receiver software running on my PC. The sensor is placed in my mailbox 4 stairs below.

Receiver (software)


/resources/phyff/eagle-concept.png.thumb.png 3D preview of the board, generated using a 3D script for Eagle. /resources/phyff/pcb-exposure.jpeg.thumb.png My home-built UV exposure box. Notice the quality workmanship. Hey, it's not worse than the thermal insulation wrapping on the Apollo "lunar" module. /resources/phyff/board.jpeg.thumb.png The board. Patched to correct various PCB mistakes. /resources/phyff/case.jpeg.thumb.png This case will hold the board, the batteries and the antenna, and will be inserted in the mailbox. /resources/phyff/encased.jpeg.thumb.png The board, encased and with batteries and wires. Not very pretty, I admit. /resources/phyff/mailboxes.jpeg.thumb.png The mailboxes of my previous appartment, in the 11th district of Paris. I temporarily left the antenna outside for testing. /resources/phyff/mailbox.jpeg.thumb.png My mailbox. /resources/phyff/installed.jpeg.thumb.png The board is glued to the top of the mailbox and thus can't be seen. The "Uncle Ben's" cardboard box simulates delivered mail. You can see the infrared barrier below it.