With each contact you make, the red LED lights up, the buzzer beeps and ... with only an Arduino UNO, ultrasonic sensor, force-sensitive resistor (or push button), and piezo buzzer.

Let it hit your red LED and you’ve lost a point. But if you can push your button ... box is an Arduino Uno and a 9V battery, plus a current-limiting resistor and the all-important buzzer.

This clock tells time with the help of some WS2812B RGB LED. [Dushyant] debugged the clock with a regular Arduino ... The alarm can interface with just about any sensor, and can be controlled ...