Hello!

This is a tutorial for beginners, that will help you create a "Mystery Box" that will only open after using all three inputs (HC-SR04 Ultrasound sensor, Photoresistor, and an NTC Thermistor).

After gathering all needed items, you can wire them like I did in this Fritzing Diagram:

For the NTC Thermistor I used a 10k resistor.

For the Photoresistor I used a 5k resistor.

You can use regular 220 ohm resistors for the LEDs.

You can position the "sensors" how you'd like it the most in the box, but for me, this was the most easy and effective way.

Coding the Arduino board:

After complete wiring, you can pass on to programming the Arduino board.

const int blitzled1 = 9;
const int blitzled2 = 8;
const int redled = 7;
const int orangeled = 6;
const int yellowled = 5;
const int blueled = 4;
const int fotor = A0;
const int temp = A1;
int valu = 0;
int fot = 0;
int trigPin = 11;
int echoPin = 12;
long duration, cm, inches;
int ledState = LOW;
int steps = 1;
unsigned long previousMillis = 0;
const long interval = 100;

unsigned long currentTime  = 0; 
unsigned long pastTime     = 0;
int           currentState = 0;
unsigned long seconds = 0;
#include <Servo.h>
Servo myservo;
void setup() {
pinMode(blitzled1,OUTPUT);
pinMode(blitzled2,OUTPUT);
pinMode(redled,OUTPUT);
pinMode(orangeled,OUTPUT);
pinMode(yellowled, OUTPUT);
pinMode(blueled, OUTPUT);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(fotor, INPUT);
pinMode(temp, INPUT);
myservo.attach(10);
Serial.begin(9600);
myservo.write(100);
startup();

}

void loop() {
  if (steps == 1) {
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, HIGH);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
  digitalWrite(trigPin, LOW);
  delayMicroseconds(5);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  cm = (duration / 2) / 29.1;
  if (cm > 7 && cm < 9)
  {
    pastTime    = currentTime;
    currentTime = millis();
    unsigned long timePassed = currentTime - pastTime;
    if (timePassed >= 1000);
            {
            seconds ++;
               pastTime = currentTime;
               blitz();
            }
   if ( seconds == 20 ) {
    Serial.print("Done!");
    Serial.println();
    seconds = 0; 
    steps = 2;
    Serial.print("Step 2");
    digitalWrite(blitzled1, LOW);
    digitalWrite(blitzled2, LOW);
  }
  Serial.print(cm);
  Serial.println();
  delay(50);

}
}
  if (steps == 2) {
  int plm = 0;
  digitalWrite(orangeled, HIGH);
 valu = analogRead(fotor);
 plm = map(valu, 0, 1023, 0, 100);
 Serial.print(plm);
 Serial.println();
 if (plm > 0 && plm < 6)
{
    pastTime    = currentTime;
    currentTime = millis();
    unsigned long timePassed = currentTime - pastTime;
    if (timePassed >= 1000);
            {
            seconds ++;
               pastTime = currentTime;
               blitz();
            }
   if ( seconds == 20 ) {
    Serial.print("Done!");
    Serial.println();
    seconds = 0; 
    steps = 3;
    Serial.print("Step 3");
    digitalWrite(blitzled1, LOW);
    digitalWrite(blitzled2, LOW);
    
  }
    
  Serial.println();
  delay(50);
  
}
}
  if (steps == 3) {
    digitalWrite(yellowled, HIGH);
int temps = analogRead(temp);
int tempsp = map(temps, 0, 1023, 0, 100);
 Serial.print(tempsp);
 Serial.println();
if (tempsp >= 53)
{
    pastTime    = currentTime;
    currentTime = millis();
    unsigned long timePassed = currentTime - pastTime;
    if (timePassed >= 1000);
            {
               seconds ++;
               pastTime = currentTime;
               blitz();
            }
   if ( seconds == 10 ) {
    Serial.print("Done!");
    Serial.println();
    seconds = 0; 
    steps = 4;
    Serial.print("Step 4");
    digitalWrite(blitzled1, LOW);
    digitalWrite(blitzled2, LOW);
    
  }
    
  Serial.println();
  delay(50);
  
}
}


  if (steps == 4) {
  int plmz;
  int valuz;
  digitalWrite(blueled, HIGH);
 valuz = analogRead(fotor);
 plmz = map(valuz, 0, 1023, 0, 100);
 Serial.print(plmz);
 Serial.println();
 if (plmz >= 75)
{
    pastTime    = currentTime;
    currentTime = millis();
    unsigned long timePassed = currentTime - pastTime;
    if (timePassed >= 1000);
            {
            seconds ++;
               pastTime = currentTime;
               blitz();
            }
   if ( seconds == 20 ) {
    Serial.print("Done!");
    Serial.println();
    seconds = 0; 
    steps = 5;
    Serial.print("All done!");
    digitalWrite(blitzled1, LOW);
    digitalWrite(blitzled2, LOW);
    myservo.write(0);
    
  }
    
  Serial.println();
  delay(50);
  
}
}

}
void blitz() {
  unsigned long currentMillis = millis();
    if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
unsigned long previousMillis = 0;
const long interval = 100;
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }
    digitalWrite(blitzled1, ledState);
    delay(100);
    digitalWrite(blitzled2, ledState);
  }
}

void startup() {
  digitalWrite(blitzled1, HIGH);
  delay(1000);
  digitalWrite(blitzled2, HIGH);
  delay(1000);
  digitalWrite(redled, HIGH);
  delay(1000);
  digitalWrite(orangeled, HIGH);
  delay(1000);
  digitalWrite(yellowled, HIGH);
  delay(1000);
  digitalWrite(blueled, HIGH);
  delay(3000);
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
  delay(1000);
  digitalWrite(blitzled1, HIGH);
  digitalWrite(blitzled2, HIGH);
  digitalWrite(redled, HIGH);
  digitalWrite(orangeled, HIGH);
  digitalWrite(yellowled, HIGH);
  digitalWrite(blueled, HIGH);
  delay(150);
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
  delay(150);
  digitalWrite(blitzled1, HIGH);
  digitalWrite(blitzled2, HIGH);
  digitalWrite(redled, HIGH);
  digitalWrite(orangeled, HIGH);
  digitalWrite(yellowled, HIGH);
  digitalWrite(blueled, HIGH);
  delay(150);
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
  delay(150);
  digitalWrite(blitzled1, HIGH);
  digitalWrite(blitzled2, HIGH);
  digitalWrite(redled, HIGH);
  digitalWrite(orangeled, HIGH);
  digitalWrite(yellowled, HIGH);
  digitalWrite(blueled, HIGH);
  delay(150);
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
  delay(150);
  digitalWrite(blitzled1, HIGH);
  digitalWrite(blitzled2, HIGH);
  digitalWrite(redled, HIGH);
  digitalWrite(orangeled, HIGH);
  digitalWrite(yellowled, HIGH);
  digitalWrite(blueled, HIGH);
  delay(150);
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
  delay(150);
  digitalWrite(blitzled1, HIGH);
  digitalWrite(blitzled2, HIGH);
  digitalWrite(redled, HIGH);
  digitalWrite(orangeled, HIGH);
  digitalWrite(yellowled, HIGH);
  digitalWrite(blueled, HIGH);
  delay(150);
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
  delay(150);
  digitalWrite(blitzled1, HIGH);
  digitalWrite(blitzled2, HIGH);
  digitalWrite(redled, HIGH);
  digitalWrite(orangeled, HIGH);
  digitalWrite(yellowled, HIGH);
  digitalWrite(blueled, HIGH);
  delay(150);
  digitalWrite(blitzled1, LOW);
  digitalWrite(blitzled2, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(orangeled, LOW);
  digitalWrite(yellowled, LOW);
  digitalWrite(blueled, LOW);
}

Done!

The project is now complete!

After completely wiring your Mystery Box and setting it up, you can now proceed to uploading the code to your Arduino Board.

The box will need this 4 steps in order for the servo to open and let you take a look inside.

1. Step 1: You will need to place something or your palm at 8 CM distance to the Ultrasonic Sensor.
2. Step 2: You will need to cover the Photoresistor so the value will be less than 7.
3. Step 3: You will need to heat the Thermistor a bit, so the value will increase.
4. Step 4: You will have to go back to step 2, but this time add light to it so the value increases to more than 75.

*Do not forget to adjust the values in the code, as for what you want it to do. (Change distance, temperature, or light values).

You can also improve the box, and add more sensors to make it more difficult.

I used this box to give my girlfriend a gift that could fit into the box, after she opened it. It took her about 2 hours and it said it was very challenging.

Have fun making this Mystery Box, and let me know what other features you'd add or already added to it.