I designed the circuit to be enabled by the tach signal. If the signal is lost for any reason the circuit board shuts down and the engine runs on the original governor. The engine speed is initially set with the original governor and any speed droop actuates the solenoid, pulling the rack and holding it until the speed sensor senses that the correct rpm has been achieved, Once the speed has recovered the cycle will start over again if the load pulls the sensor voltage down. (lower voltage from the small PM motor) Unlike the original governor the IC chip is extremely sensitive to voltage changes and responds within a millisecond to correct the engine speed. This is essentially a "bang bang" control running at high processor speed, so sensitive and fast that it is almost unnoticeable. I'm using a 12-24 vdc Ledex tubular solenoid attached to the governor arm at the dimple just above the governor spring adjustment knob. I'm still running reliability tests so that is why i haven't been saying anything about it. I want to be sure of the design and longevity before I put them up for sale. It is simple to install and adjust for any desired speed by means of 2 pots, one for matching the system voltage to the chip setpoint and one for tuning the tach voltage to the board.
I also see a place that can be improved. I'm using a single IC chip to control the speed. A version could easily be made using a quad chip that could energize a shut down solenoid if the tach voltage goes above the auxiliary chip setpoint, another of the quad's chips could monitor temp using a thermal switch or thermister, and the 4th IC chip could monitor oil level via a float switch. If the first version works out I "may" build a type II board. Additionally, a second quad IC could initiate an autostart sequence, but that is something I'd want to think about for the future. Its starting to get away from the KISS principle. It is doable but would have someone unaccustomed to motion control negative feedback loops, integrated circuits, and electronics scratching their heads most likely. Can you say flow chart and boolean algebra? It makes my head hurt sometimes!
