Imagesource: https://unsplash.com/

And since we're on the subject of electronics, here's another little gem that shouldn't be missing from any link collection. 

Bill Bowden has compiled a whole army of different circuits, which can be useful every now and then. For each of them there is a schematic and a short explanation.

Whether the whole thing is useful depends entirely on the reader, so decide for yourself.

Only drawback: Comic Sans 😄 - (I thought the font would be banned today on pain of death).