I'm researching timed relays right now.
Almost finished the edger itself. I was having a heck of time getting the boards to feed straight. I just installed a thin piece of metal behind the fixed blade to act as a fence and it now appears to be working. I just have to guide the board for the first foot or so until it starts pushing against the fence. I may revisit this later on and add in-feed and out-feed conveyor belting instead.
Had a bit of a scare. The spring that keeps tension on the idler for the belt decided to break. The belt proceeded to ride up onto the edge of the sheave. In the few revolutions the engine made before I managed to shut it of, it bent the saw blade shaft making one of the blades impact the protective top cover. Made a nice gouge in it! Back to the parts store for a new shaft and blade.