LED triggered by LDR

The setting for the LDR exercise is the same as the button exercise except that the button is replaced by LDR(light dependent resistor) which leads to the environment light brightness as the factor controlling the LED's on/off. It is a simple interesting sensor-based electrical circuit.

The 2nd exercise is modified based on the previous one, but the output pin is shifted to the PWM which conveys not only the yes or no value but also how much the value is and what quality the value effects the environment condition.