Question

Suppose that you use a 220 Ohm resistor as the fixed resistor in your Arduino burglar alarm.

Suppose that the photoresistor is the same one we used in our last homework assignment, where the resistance is 500 Ohms when it is fully illuminated by light, and 180 kiloOhms when it is in darkness.

What would the input voltage be to the Arduino when it is fully illuminated if we connect the Arduino so that its analog input pin "sees" the same voltage difference that the photoresistor has across it.

In the previous problem, what would the input voltage be to the Arduino when it is darkness if we connect the Arduino so that its analog input pin "sees" the same voltage difference that the photoresistor has across it.

Answer 1

Different types of light detectors are LDRs or Light Dependent Resistors Photo . First you need to connect the LDR to the analog input pin 0 on the Arduino. If intensity of light falling on LDR is high LDR will have low resistance