Inspired by Shopdogsam, mrpete222 (tubalcain) and Dave Jones, I set out to build an electric solenoid engine. I quickly find out that adding variable speed capability to existing cam and switch governor isn't as simple as it sounds. I start out with the easystepper board, move on to electromechanical relays and settle on transistors driven by a micro-controller (MSP430 LaunchPad) to achieve reliable speed control for a yet to be built model engine. The stock photo of a steam engine is complements of: Stott Park Bobbin Mill Steam Engine; Chris Allen - From geograph.org.uk