The MQTT letterbox Part 2: Sending alerts from MQTT // Project


Originally published at:

This is part 2 of my Uber letterbox where I show you how to send notifications to your phone when someone delivers a letter.
If you haven’t seen Part 1 yet, then check that out first.


Nice build. I look forward to your battery optimization tutorial and in general to your testing of the solar/battery power system - how often will it run out of power in the winter?

IIRC, you rejected the IR sender/receiver pair because it took 5ma, but doesn't the Sharp distance sensor take the same amount?

If you had time of day available, you could sleep the sensor in off hours, when it's unlikely that mail would be delivered.


Thanks mate.
I'm definitely needing some power optimizations as on cloudy days it runs out of power. This was by design anyway, as I wanted to show how much you can improve up-time with a bit of power.

I'll be using the distance sensor as an interrupt trigger to wake the sleeping ESP32, which means a change to the way the MQTT client works, but that's easy enough to do.