Abstract: The present invention is directed toward a smart dimmer switch comprises of a power semiconductor switch that automatically changes the luminous level of lamp or group of lamps as the ambient luminous level changes according to an algorithm stored in a microcontroller. The microcontroller accepts an input signal from a light sensor or group of light sensors and adjusts the phase angle of the drive signal to the driver circuit of the power semiconductor switch through an opto-coupler using a software algorithm to allow the luminous output of the lamp or light fixture to be higher or lower than the preset luminous output level, in order to maintain a constant ambient luminous level selected by the users. The software algorithm, together with a non-volatile memory and the microcontroller, allows the desired ambient luminous level to be retained even when the AC supply power is cut off from the smart dimmer switch.