Transferring the digital clock circuit to a perfboard and putting it into an enclosure.
Sleep mode and Schmitt trigger on multiplexed analog buttons. Also, now the clock is powered by 18650 Li-ion cell.
Broken OLED color screen on Quicko T12-952 can be replaced with generic 128x32 I²C monochrome OLED.
Replacing Arduino Nano with regulatorless Arduino Pro Mini.
I cut off the voltage regulator from the Pro Mini board. Board works fine, but now requires external regulation.
Arduino Pro Mini clone’s regulator fried when connected with 12V power supply.
Arduino Pro Mini tryout with 128x32 I²C OLED display.
Adding buttons, alarm buzzer, temperature and humidity sensor, brightness potentiometer, and menu system.
Transferring the circuit to a bigger breadboard.
Adding the LCD display for the Arduino-based digital clock.