SunFounder 3in1 Kit
In this circuit, the 10K resistor and the photoresistor are connected in series, and the current passing through them
is the same. The 10K resistor acts as a protection, and the pin A0 reads the value after the voltage conversion of the
photoresistor.
When the light is enhanced, the resistance of the photoresistor decreases, then its voltage decreases, so the value from
pin A0 will increase; if the light is strong enough, the resistance of the photoresistor will be close to 0, and the value
of pin A0 will be close to 1023. At this time, the 10K resistor plays a protective role, so that 5V and GND are not
connected together, resulting in a short circuit.
If you place the photoresistor in a dark situation, the value of pin A0 will decrease. In a dark enough situation, the
resistance of the photoresistor will be infinite, and its voltage will be close to 5V (the 10K resistor is negligible), and
the value of pin A0 will be close to 0.
The calculation formula is shown below.
(Vp/5V) x 1023 = Ap
Wiring
122 Chapter 4. Basic Projects
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