This document describes the construction of a small frequency counter using a PIC microcontroller and several seven-segment LED digits. Frequency range: 1 Hz to 50 MHz Five-digit resolution (display options include x.xxxx kHz, x.xxxx MHz, or xx.xxx MHz) Measuring signal amplitude up to 30 V Capable of measuring 4-40 MHz passive crystals Automatic range switching with different gate times Optional frequency offset addition or subtraction (programmable) Low component count: includes one PIC 16F628 microcontroller, five 7-segment LED displays, one 20 MHz crystal, and a few resistors Optional configurable power-saving mode that activates when frequency remains stable for 15 seconds Compatible with USB 5V or DC 5-12V power supply Package includes: 1 x DIY kit 1 x USB cable