Amazon DRS-enabled toilet paper shelf orders TP when the supply is low. It's a low power, battery powered thing with wifi enabled microcontroller and basic digital sensor. The shelf is slightly inclined, allowing TP to roll down like boulders in Supaplex
The device is powered by ESP8266. It is a wifi enabled microcontroller with just two GPIO pins. When the last roll of TP is available on the tray, the microcontroller orders more TP from Amazon.
To conserve power, the microcontroller is probing the TP availability only once in a while by setting high voltage on one of its GPIO pins. It senses the voltage on another GPIO pin. Two consecutive low measurements on the sensor will order more TP.
Once the basic behavior is implemented, there are a few ways to enhance the project:
- build a simple yet beautiful web configuration for entering Amazon credentials and picking your favorite TP.
- implement a watchdog that notifies me when the battery runs out and the device stops pinging the watchdog.