Hydrogen! It’s a highly flammable gas that seems way too cool to be easy to come by. And yet, it’s actually trivial to make it out of water if you know how. [Maciej Nowak] has shown us how to do just ...

This is a very simple square wave generator circuit built with IC 74LS00 that can generate square signals with frequencies between 20 Hz and 1 MHz. Its stability is good enough for most applications.