Frequency counters are devices that can measure the frequency of a signal. They are used in a wide variety of applications, including electronics, telecommunications, and audio engineering.
Here is a video where I will show you how to build a simple frequency counter for audio frequencies using an Arduino UNO and a few extra components:
Here, instead, is another video where I will show you another way to build a frequency counter with an Arduino UNO, but capable of measuring frequencies between 1 Hz and 7 MHz. Practically, this can be used as a cheap lab frequency counter, with a precision of about 1%:
And here is all you need to make your own (both versions):
eleneasy.com 