Testing the timer
This section shows how to test out the 20-second timer.
Once you insert the electronic circuit with the sensor, the Blue Pill, and the LCD in a protective case, try it in a bathroom. Carefully place it close to a hand washing sink if you can, to facilitate activating it and seeing the counting while you wash your hands. See whether you can fix it to a wall or a surface so it won't move and that no one accidentally knocks it over while waving at it. Safety first!
You should connect the Blue Pill to a portable power bank that has a USB socket. This is to avoid connecting the Blue Pill to a wall USB adapter to make it safer to use in an environment such as a bathroom, as shown in Figure 14.11:
Figure 14.11 – A power bank connected to the Blue Pill microcontroller board
You can test out everything with a small power bank, such as the one shown in Figure 14.11.
Try activating the timer by waving at the sensor numerous...