This 4 -digit 7-segment display section is wired around four common-cathode 7-segment LED displays, and four BC547 npn transistors. The 1K resistors are used for base current limiting, and the 390R ...

With seven LEDs for each digit, that works out to 3,584 4,096 individual LEDs for the entire panel. To power and control this gigantic array of LED displays, each row uses a PIC16F microcontroller ...