A sensor activated unit, e.g., a drinking fountain or a wash basin, for preventing unwanted operation. The sensor has a power on reset circuit that makes use of a resistor capacitor network and a voltage threshold comparing device to create a time delay that will inhibit the operation of the unit for a nominal predetermined time period when current is first supplied to the sensor. The sensor does not activate until a user steps up to the unit and is within a preset range or distance from the unit. Use is made of an infrared sensor for controlling the operation of the unit. Circuitry is provided to control the time of commencement of the operation of the unit, the time period duration of operation, and down time of the unit before it is readied for operation again.