Lab set Program-7

 7. Develop a program to read the pH value of a various substances like milk, lime and water.

Objective

To develop a program that reads and classifies the pH value of various substances such as milk, lime water, and pure water using Arduino.
(Simulated using a potentiometer in Tinkercad since the actual pH sensor is unavailable.)

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Learning Outcomes

After completing this experiment, students will be able to:

1. Understand how a pH sensor works and its output behavior.

2. Simulate sensor readings in Tinkercad using analog components.

3. Map analog readings to real-world pH ranges (acidic, neutral, basic).

4. Write Arduino code for data classification and serial monitoring.

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Components (from Tinkercad Palette)

• Arduino Uno board

• Potentiometer (as pH sensor)

• 3 LEDs (Red = Acidic, Green = Neutral, Blue = Basic)

• 220 Ω resistors × 3

• Breadboard

• Jumper wires

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Circuit Wiring (Exact)

1. Potentiometer (pH Sensor substitute)

   • One outer leg → 5 V

   • Other outer leg → GND

   • Middle pin → A0

2. LEDs

• Red LED → Pin 9 (through 220 Ω resistor to GND)

• Green LED → Pin 10 (through 220 Ω resistor to GND)

• Blue LED → Pin 11 (through 220 Ω resistor to GND)

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Arduino Sketch

int phPin = A0;
int redLED = 9;
int greenLED = 10;
int blueLED = 11;
float phValue = 0.0;

void setup() {
  pinMode(redLED, OUTPUT);
  pinMode(greenLED, OUTPUT);
  pinMode(blueLED, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(phPin);

  // Convert analog (0–1023) to pH scale (0–14)
  phValue = map(sensorValue, 0, 1023, 0, 14);

  Serial.print("Analog Reading: ");
  Serial.print(sensorValue);
  Serial.print(" | pH Value: ");
  Serial.println(phValue);

  // Classification
  if (phValue < 6.5) {              // Acidic
    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);
    digitalWrite(blueLED, LOW);
  } 
  else if (phValue >= 6.5 && phValue <= 7.5) {  // Neutral
    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, HIGH);
    digitalWrite(blueLED, LOW);
  } 
  else {                            // Basic
    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, LOW);
    digitalWrite(blueLED, HIGH);
  }

  delay(500);
}

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How It Works

1. The potentiometer simulates different pH levels:

   • Turning it left → low analog value → acidic.

   • Middle position → around neutral (7).

   • Turning right → high value → basic.

2. Arduino reads analog values from A0 (0–1023) and maps them to pH 0–14.

3. The corresponding LED lights up:

   • Red → Acidic (e.g., milk, lemon juice)

   • Green → Neutral (e.g., pure water)

   • Blue → Basic (e.g., lime water, soap solution)

4. pH values are displayed on the Serial Monitor.

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Common Mistakes & Quick Fixes

Issue	Cause	Fix
LEDs not glowing	Missing resistor or wrong pin mapping	Verify wiring and resistors
pH readings unstable	Loose breadboard connection	Re-insert jumper wires
Wrong LED lighting	Reversed LED polarity	Longer leg → digital pin side

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Viva / Check-Your-Understanding

1. What is the pH range of acidic, neutral, and basic substances?

2. What is the function of a pH sensor?

3. How did we simulate the pH sensor in Tinkercad?

4. What are typical pH values of milk, water, and lime water?

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Extensions (Mini-Tasks)

• Display the pH value on an LCD instead of Serial Monitor.

• Use a buzzer to alert when the sample is too acidic or too basic.

• Expand to detect more categories (strong acid, weak acid, etc.).

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Lab Record (Suggested Headings)

1. Title

2. Objective

3. Components Used

4. Circuit Diagram (Tinkercad screenshot)

5. Arduino Code

6. Output / Simulation Result

7. Viva Questions & Answers

8. Extensions

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Tinkercad Link

https://www.tinkercad.com/things/2EPEgTk14FZ-labset-prog-7