The multi wifi switch is based on a plain ESP 12F chip. It sends button presses over MQTT to a broker. The box has 4 buttons and 1 LED and is relativly dumb. It relies on an external controller (like Home Assistant, IoBroker, ...) for intrepetting the button presses.
The ESP is most of the time in deep sleep. It only wakes up, when a button is pressed. In deep sleep the circuit needs only arround 17 µA. The time needed for waking up, connecting to the wifi, connecting to the MQTT broker and going back to sleep is for my setup between 0,75 - 3 seconds. While it is up and sending data the circuit consumes on average arround 100 mA.
So, pressing a button needs
- at best
0,75 s * 100 mA = 75 mAs = 0,02 mAh - at worst
3 s * 100 mA = 300 mAs = 0,08 mAh
Sleeping a whole day without pressing any buttons needs
24 h * 0,017 mA = 0,4 mAh
A typical LiFePo4 18650 battery has 1500 mAh. If we assume there are 10 button presses every day, we need in the worst case 10 * 0,08 mAh = 0,8 mAh. The rest of the day, the device is in deep sleeps which consumes approximately 0,4 mAh. In total 0,8 mAh + 0,4 mAh = 1,2 mAh is needed . With a full charge of the battery it will last arround 1500 mAh / 1,2 mAh = 1250 days = 3,4 years. Pressing the button more often will drastically decrease runtime.
Every button can distinguish between two button presses:
- Short press
- Long press (Press as long as the LED is on, to ensure a long press is recognized)
The LED is on, while the ESP is active. As soon as it is off again, the data is sent. If no wifi connection was possible it will blink 5 times slowly. Blinking 10 times fastly means no connection to the MQTT broker could be established.
I don't like to share my wifi password with why there is a Secretes_dummy.h file. Fill in your configuration and rename this file to Secrets.h. The .gitignore will prevent checking in this file.
The circuit needs a voltage arround 3.3 volts. I use a LiFePo4 battery, because it already has the desired voltage and no voltage conversion is needed.
