Fourth Assignment - High(er) voltage and transistors!

Circuit

Schematic

Calculation

Firmware

//set pin numbers
const int ledPin = 10; //the number of the lED pin
const int ldrPin = A0; //the number of the LDR pin

int sensorValue = 0; // value read from the photoresistor
int outputValue = 0; // value output that is mapped out

void setup() {
    // initialize serial communications at 9600 bps:
    Serial.begin(9600);
    //initialize the LED pin as an output
    pinMode(ledPin, OUTPUT); 
    //initialize the LDR pin as an output
    pinMode(ldrPin, INPUT);
}

void loop() {
    // read the ldrLED in value
    sensorValue = analogRead(ldrPin);        
    //map it to range of analog out
    outputValue = map(sensorValue, 0, 1023, 0, 255);        

     // When output value is equal to or less than 200, turn the LED on       
    if (sensorValue <= 200) { 
      // turn on LED      
      digitalWrite(ledPin, HIGH); 
      Serial.println("LED is ON");

    // if the output value is greater than to 200, turn the LED off
    } else {  
      // turn off LED       
      analogWrite(ledPin, 0); 
      Serial.println("LED is OFF");             
    }
}
    

Circuit's operation