US Patent 7755021 Non-toxic photo cells and photosensors including the same

Photo control devices include a housing having a light transmissive portion. A photosensor is positioned in the housing to receive light passing through the light transmissive portion of the housing. A relay electrically coupled to the photosensor is responsive to a level of light detected by the photosensor. The photosensor includes a light sensitive silicon photo cell and an electronic circuit. The electronic circuit is coupled to the silicon photo cell and the relay and includes a field effect transistor (FET) including a zener diode therein between a source and a drain of the FET. The silicon photo cell may be a photodiode and/or a phototransistor. The relay may be a thermal switch including a heater resistor.