This document describes the construction of small frequency counter with a cheap PIC microcontroller and a few seven-segment LED digits.

- Frequency range 1 Hz ... 50 MHz

- Five digits resolution (display for example x.xxxx kHz, x.xxxx MHz,

or xx.xxx MHz)

- Measuring signal amplitude can be up to 30 v

- 4-40 m passive crystals can measure

- Automatic range switching with different gate times

- Optional addition or subtraction of a frequency offset (programmable)

- Very low component count: a PIC 16F628, 5 7-segment LED displays, a 20MHz crystal and a few resistors

- Optional (configurable) power-saving mode which automatically turns

- The display off if the frequency didn't change significantly within 15seconds

- USB 5V or DC5-12V power supply can be used