A guide to wiring an RTC module over I2C to keep accurate time and date even after power is disconnected.
Enter a servo motor's rotation angle digitally via a 4x4 keypad, with input validation before it's applied.
Control an RGB LED's color with any infrared remote control, by decoding button codes and blending colors using PWM.
Program a three-LED traffic light using a simple millis()-based state machine, with realistic timing for each phase.