This is a simple 0 to 9 counter circuit constructed using Arduino! Here, a common cathode 7-segment LED display is connected to Arduino for displaying the digits.

The ultralow-cost, two-digit- counter circuit in Figure 1 represents an attempt to reduce the number of components using a mostly software approach and a low-cost microcontroller, the PIC16F84A.

Already, a couple of years back he wrote an Arduino-based Microtronic emulator. In his new project, he got around to extending the functionality and creating a custom PCB for the device.