Abstract: An on demand, non-contact sensor controlled flush valve actuation system includes a flush valve between a water supply and a plumbing fixture. An actuator for the flush valve includes a moveable piston in fluid communication with a control water inlet, with a control water conduit carrying water from the flush valve through a solenoid operated control valve to the actuator assembly. A radiation sensing/detecting unit generates a first control signal in response to the return reflection of infrared radiation. A timer receives the first control signal and, in response thereto, generates a second control signal of a predetermined duration which activates the solenoid. When the solenoid is activated, a portion of the pressurized supply water flows into the actuator assembly and against a piston therein, with the piston moving to operate a trip mechanism for the flush valve.