LIGHT is a light intensity sensor unit with an adjustable photoresistor。
A photoresistor is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity, and vice versa. It exhibits photoconductivity which make it possiable to detect the varies based on Voltage, and use a AD to convert the digital data.
We add some extra work to strengthen the circult, a Dual Differential Comparators LM393, compares the differntial voltage between the photoresistor and the varistor. It could offer larger and accuracy range of light intensity.