Microcontroller will act as switch master, for that you need to connect the relay for switching, wherein uC will provide the signal for switch the relay...
then you need sensors to be connected like temp sensor, for that you need to connect it with ADC if you are using 8051...
And you need a light sensor for that you can use Photodiode Light Sensors, Optical detectors or something....
Now firstly you need to decide wat controller you are going to use based on the above requirement, and if anything else that you want....