Here is a simple, yet useful circuit of an Arduino 4-digit 7-segment LED display unit. The module used here is a self-contained, compact common-cathode module containing four 7-segment LED numeric ...

Just follow the schematic circuit diagram ... is added between ground rail (0V) and the common cathode pins (3 & 8). It is better to directly connect pins 3 & 8 of the display to ground rail. Next add ...