Make This Handy Zener Meter For Faster Testing

The Handy Zener Meter is designed to test and measure the breakdown voltage of Zener diodes quickly and accurately. At the heart of the system is an ATtiny85 microcontroller, which orchestrates the measurement process and interfaces with a compact 2.4cm 128x64 pixel OLED display via the I2C protocol. Power is supplied by a 9V battery, which is regulated down to a stable 5V via a 7805 voltage regulator (IC1) to safely power the ATtiny85 microcontroller and logic circuitry. To test Zener diodes that require higher breakdown voltages, the circuit incorporates an LM2577-based buck-boost converter module (Board1). This module steps up the voltage, capable of reaching up to 40V DC, allowing the device to sweep across a wide range of diode thresholds. A 2N2222 transistor (T1) acts as a switching element controlled by the ATtiny85, enabling and disabling the high-voltage test path safely. When a Zener diode is placed under test, the stepped-up voltage is applied through current-limiting passive components (resistors and capacitors) until the diode reaches its breakdown region. The resulting voltage drop is monitored by the ATtiny85's analog-to-digital capabilities, and the measured value is instantly rendered onto the I2C OLED display using custom C code (ZenerMeter.c alongside helper libraries like oled_lib.c and font headers). Programming is accomplished using an ISP programmer and tools such as Programmers Notepad.