Test analog data reading for Arduino UNO

We need to test how to read analog data from actual circuits before completing the solar tracker experiment. In Arduino board, we use analogRead() function to read the analog data. Let's look at the usage of this function first.

Syntax:
analogRead(Pin);
where "Pin" represents the pin number of the input pin which read from. Furthermore, the return value is integers from 0 to 1023 and the analog value can be read from 0 to 5V. Therefore, the resolution of measurement is approximately 4.88mV.

In the test, we design the circuit that voltage of photo-resistor can be read via Arduino UNO. Therefore, the power supply (+5V) is connected to the resistor, one terminal of photo-resistor is connected to ground and another terminal is connected to the Arduino (e.g. A0) as shown in following Figure 1.

         
                                               Figure 1: Circuit for testing data reading
 
After that, upload the program from computer to Arduino board and then open the Serial Monitor. Observe the voltage of photo-resistor as shown in following Figure 2:

                                               Figure 2: Voltage of photo-resistor

When the strength of light increase, the voltage of photo-resistor becomes smaller as shown in following Figure 3:

                             Figure 3: Voltage of photo-resistor with increasing strength of light

When the strength of light decrease, the voltage of photo-resistor becomes larger as shown in following Figure 4:

                             Figure 4: Voltage of photo-resistor with decreasing strength of light