Patent ID: 8701703

Claim:
A gas shut-off valve assembly comprising: a valve movable between an open position that permits gas flow through the gas shut-off valve assembly and a closed position that prevents gas flow through the gas shut-off valve assembly; a motorized drive configured to move the valve between the open and closed positions; and a control circuit that includes or is associated with a pressure detection circuit and a valve position detection circuit; wherein said control circuit is configured to close the valve via the motorized drive in response to detecting a closure condition, and is further configured to initially verify valve closure based on directly or indirectly detecting movement of the valve into the closed position, and to subsequently verify valve closure based on monitoring gas pressure on a downstream side of the valve, after said initially verifying valve closure; wherein the motorized drive includes a stepper motor, and wherein the control circuit is configured to generate stepper motor control signals, for moving the valve between the open and closed positions; wherein the valve position detection circuit comprises a counting circuit to count stepper motor signal pulses applied to the stepper motor by the control circuit, a back electromotive force (EMF) sensing circuit to sense a back EMF of the stepper motor, and a position inferring circuit configured to infer the position of the valve based on counting stepper motor pulses applied to the stepper motor in conjunction with sensing characteristic changes in the back EMF of the stepper motor at count ranges that are associated with the open and closed positions of the valve; and wherein the control circuit comprises a microprocessor that includes at least the counting circuit and the position inferring circuit of the valve position detection circuit.