This was a quick project to add notifications for when I get real physical mail. This is something I’ve had on my mind since I made my first SMS doorbell notification system back in 2004 and I finally got around to it last month.
First of all I picked up a cheap internal letterbox flap and fixed that over the internal side of the letterbox opening. Then I took a microswitch that I had salvaged out of an old dot matrix printer some time ago and made a little right angle bracket from some perforated metal strip I had lying around. A few little adjustments to the microswitch actuation lever and I had it operating the switch as soon as the flap was moved even only slightly. It also operates it as it closes but that is easily taken care of in code to prevent duplicate notifcations and can also be used to detect if something is stuck part way through the letterbox instead of being pushed all the way through.
I connected the switch to a TinyTX3 running the same code as I use for reed switches and my doorbell which uses a pin change interrupt to sends a notification via the RFM12B wireless network which is then picked up by the Tiny328 connected to my server. From there Node-RED alerts me via speech and my LED matrix display if I am in or if I am out it sends me a notification via Whatsapp.
For now this is connected to its own dedicated TinyTX but I’ve somehow ended up with no less than 4 TinyTX nodes in close proximity around the door (doorbell, letterbox, outside temperature and hall temperature/air pressure) so I am working on a new node to combine these into one unit as well as adding some more features for controlling LED porch lights and so on. At the moment it is looking like this will be an ESP8266 node so watch this space.