My nephew recently made an inquiry as to the possibility of creating a low cost non contact digital tachometer.  With my typical over-optimism, I nearly shrieked "No problem!  Piece of Cake!".  This didn't turn out to be entirely true, but the demonstration project I put together was pretty straight forward. The first thing I needed was an optical sensor.  Obviously ambient light can be a problem, so I wanted something tuned to infrared.  As fortune would have it, someone had the brilliant idea of putting an infrared emitter (LED) and a detector (a phototransistor) in the same case!  The sensor I ended up using is an Omron EE-SF5. For...

Read More »