My Stirling Engine: speed check

When I ran my engine for the first time, I couldn't believe how fast it was going.

 

Naturally I was curious.

So I had to build a simple tacho to check the speed.

Don't Waste Power With L.E.D.s

I've been playing with a mixed bag of white LEDs to work out how many I need to illuminate BirdBox 2014.

As this project is battery powered, I want to minimise power consumption where possible to extend battery life.

Like all 5mm LEDs, there is no obvious way to determine what exactly they are (i.e. there are no part numbers). And as this is a mixed bag, I need to sort them by type before including any of them in my circuit.