This project will help you to easily develop an Arduino compatible project that requires 4 x -7Segment 0.5″ displays. The project consists of an Atmega328 microcontroller, 4 x BC847 NPN transistors to drive the common cathode displays. All displays are used in multiplexing configurations. The circuit operates with 5V DC and consumes a few milliamps. Arduino code is provided to test the board. The code is pretty simple, it will read 0 to 5V on analog pin A0 and display 0 to 1000 display, basically 0 to 5V mapping to 0-1000. Users may write their own code to read an analog voltage from a sensor or other source and display it on the 4 x 7segment displays.
Arduino 4-Digit 0.5″ Common Cathode 7 Segment Display Module – [Link]