Description

Timer to help your kids brush their teeth properly. 2 minutes in total. Shows which part of the mouth to focus on and displays a smiley face when finished.

Hardware required

• Arduino Nano (or its clone, works both on ATmega168 and ATmega328)
• SSD1306 0,96'' OLED display
• 2x 10kΩ resistor (when using ATmega168)
• 9V battery connector + 9V battery
• mini toggle switch (on/off)
• a few wires to connect everything

Arduino source code

https://github.com/mkosiedowski/tooth-brushing-clock

Wiring

https://www.instructables.com/Monochrome-096-i2c-OLED-display-with-arduino-SSD13/

Basically, connect:

Arduino A4 to SDA display input
Arduino A5 to SCL display input
Arduino GND to display GND
Arduino 5V to VCC display input
With ATmega 168 based Arduino Nano you will most probably need a pull-up resistor on SCL & SDA inputs of your OLED screen. Just connect them to proper A4/A5 output ports of your Arduino board and also connect them through 10kΩ resistor to 5V output of your board

Connect 9V battery:

(+) to one of the switch ports
connect the second port of the switch to VIN in the Arduino board
(-) to GND in the Arduino board

Print instructions

Prints well with PLA, 0.2mm layer. Use supports (you can add it everywhere, it's easy to remove them after printing).

Assembly

9V battery goes to the right side of the case
Arduino nano goes to the left side of the case
switch goes to the back of the case
Display slides into the socket in front
Lid snaps into the latch on top
Ready!