Testing out the photoresistor

This section focuses on how to test out a photoresistor to see if it is working OK. First of all, remember that the photoresistor used in this chapter does not have polarity, so you can safely connect any of its pins (legs) to a microcontroller board's input port.

You also need to make sure that the pull-down resistor connected to the photoresistor has the right value. For example, the pull-down resistor used in the Blue Pill example from Figure 4.4 is 10K ohm, and we used a 220-ohm resistor for the Curiosity Nano example from Figure 4.6. We found those resistor values experimentally. You can try out different resistors connected to the photoresistor to see if the voltage passing through the photoresistor changes widely. Ideally, that voltage should be changing between 0 and 3.3 volts, or close to those values, because in our circuit examples from this chapter, we connected one pin of the photoresistor to 3.3 volts.

In order to see if the photoresistor...