3-minute counter with a Traffic Light LEDs. A switch controls to start, reset, and restart the timer.

Parts list

Arduino Uno (1)

7-segment LED (2)

LED (Green, Yellow, Red)

Resister 220 Orm (3)

Perfboard (1)

JSP 2-pin connector male/female pair (1)

Push-button (1)

9V Battery case with a switch

Wires

Source Code

Download them from the Git repository

countdownTimer.ino

SevenSeg.h (not mine)

SevenSeg.cpp (not mine)