LED Binary Clock Circuit using Arduino

The LED Binary Clock system centers around an Arduino Nano microcontroller that processes real-time data and drives a matrix of 20 LEDs to display time in binary format. Timekeeping is maintained by a DS1307 Real-Time Clock (RTC) module, which relies on an external 32.768kHz crystal to accurately track seconds, minutes, and hours. The DS1307 communicates continuously with the Arduino Nano via the I2C protocol, utilizing the Wire.h and RTClib.h software libraries. When a 3V coin cell is installed in the RTC module, it acts as a backup power source, ensuring the time is preserved during power interruptions. To efficiently drive 20 LEDs without requiring an excessive number of dedicated microcontroller pins, the circuit uses multiplexing supported by 6 PNP transistors (such as BC557A or 2N5087) acting as high-side switches, alongside 1k and 10k resistors to manage current flow and transistor base biasing. The TimerOne.h library is often employed to handle precise timing intervals for refreshing the multiplexed display smoothly. All of these discrete components are integrated onto a professionally designed custom PCB created using EasyEDA, translating schematic logic into a compact, functional circuit board powered by a safe low-voltage DC source.