Use LDR instead of potmeter

In order to use the LDR, we must first of all ensure that we can read LDR. We have to 'tell' the Arduino to which pin we connected the LDR. For the sake of convenience, we also make a constant for this, similar to the potmeters:

// Init the Pins used for 10K pots
const int redPotPin = 0;
const int greenPotPin = 1;
const int bluePotPin = 2;

// Init the LDR pin
const int LDRPin = 5; // <<add this line
Then we need to see where in the code the value of the potentiometer is read, so that it can be replaced by the LDR. This will be done in the next line code:

currentColorValueRed = (255 - folder( analogRead(redPotPin), 0, 1024, 0, 255 ) );

This line is a rather complex line code, because a lot happens at the same time. Before we modify the rule, let's see if we can make the code a bit more understandable, by dividing it into steps. That would be something like that:

// read the value of the potmeter and save the result in variable measurementValue

int measurementValue = analogRead(redPotPin);

// read the convert value (we will come back to this later)

int measurementValueMapped = folder(measurementValue, 0.1024.0.255);

// subtract this value from 255. You do this because the led is connected in such a way that it is 
// on if you set the value 0 in currentColorValueRed, and off at 255

currentColorValueRed = (255 - measurementValueMapped);

You can see that reading out the potentiometer is actually done in the first line using the 'analogRead' function. This function allows the Arduino to make a measurement on the pin, which you give between the round hooks. In this case the redPotPin. This could be replaced by LDRpin. The modified code becomes the LDRpin:

currentColorValueRed = (255 - folder( analogRead(LDRpin), 0, 1024, 0, 255 ) );

Define range LDR

Then, of course, we must also change the place where a message is written to the serial monitor:

Serial.println(analogRead(LDRPin));

You can adjust the amount of light that falls on the LDR by clicking on the LDR in simulation mode and then moving the slider that appears back and forth.

The value that can be measured in simulation varies (approximately) from 5 to 657 instead of 0 to 1023.

The reason that the potentiometer only goes up to 657 and not up to 1023 has to do with the fact that we have connected a resistor in series with our LDR in the circuit. Over this resistor falls a part of the voltage, which the Arduino offers.

The reason that the potentiometer only goes up to 5 and not to 0, has to do with the fact that our LDR, no matter how much light we shine on it, still has a little resistance. Part of the Arduino's power therefore always goes through the LDR.