9. Input Devices

group assignment: • probe an input device’s analog levels and digital signals

individual assignment: • measure something: add a sensor to a microcontroller board that you have designed and read it

I tested the following sensors: Push Button Turbidity sensor

Turbidity Sensor

Measured water quality using turbidity sensor in preparation to my final project. Turbidity sensor measures the cloudiness of a liquid caused by suspended particles. These particles scatter the incident light.

How Turbidity sensor works Turbidity sensors measure the amount of light that is scattered by suspended solids in a liquid, such as water. When the concentration of total suspended solids (TSS) and total dissolved solids (TDS) in a liquid increase, the turbidity also increases.

When measuring turbidity, most often, you will see the units NTU or JTU.

NTU = Nephelometric Turbidity Units JTU = Jackson Turbidity Units

I worked with turbidity and whenever it detects particles in water the led blinks and it prints on the serial.

I used chatgpt to generate the code, you can replicate the code

// Pin configuration
const int buttonPin = 0;    // D0
const int ledPin    = 10;   // D10

// Button state tracking
int buttonState;
int lastButtonState = HIGH;

// Timing variables
unsigned long lastPressTime  = 0;
unsigned long buttonDownTime = 0;

// Press logic
int pressCount = 0;

// Timing thresholds (in milliseconds)
const unsigned long doubleClickInterval = 400;
const unsigned long longPressTime       = 1000;

// LED state
bool ledOn = false;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);

  Serial.begin(115200);
}

void loop() {

  // Read button state
  buttonState = digitalRead(buttonPin);

  //  Detect button press (HIGH → LOW)
  if (buttonState == LOW && lastButtonState == HIGH) {
    buttonDownTime = millis();
  }

  //  Detect button release (LOW → HIGH)
  if (buttonState == HIGH && lastButtonState == LOW) {

    unsigned long pressDuration = millis() - buttonDownTime;

    //  LONG PRESS → Turn LED OFF
    if (pressDuration >= longPressTime) {
      ledOn = false;
      digitalWrite(ledPin, LOW);
      Serial.println("Long press → LED OFF");
      pressCount = 0;
    }

    //  SHORT PRESS handling
    else {
      unsigned long now = millis();

      // Check for double click
      if (now - lastPressTime < doubleClickInterval) {
        pressCount++;

        if (pressCount == 2) {
          ledOn = true;
          digitalWrite(ledPin, HIGH);
          Serial.println("Double click → LED ON");
          pressCount = 0;
        }

      } else {
        pressCount = 1;
      }

      lastPressTime = now;
    }
  }

  // Update last state
  lastButtonState = buttonState;
}

Push button I used push button 12mm as my input and led as output and connected this to my analog pin D0, when i press the button twice quickly the led turns on and if i hold it for 1 second it tuens off i

// Pin configuration
const int buttonPin = 0;    // D0
const int ledPin    = 10;   // D10

// LED state
bool ledOn = false;

// Timing variables
unsigned long buttonPressTime = 0;
unsigned long lastReleaseTime = 0;

// Timing thresholds (in milliseconds)
const unsigned long doubleClickTime = 400;
const unsigned long longPressTime   = 1000;

// Click tracking
int clickCount = 0;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);

  Serial.begin(115200);
}

void loop() {

  // Track button state
  static bool lastState = HIGH;
  bool currentState = digitalRead(buttonPin);

  //  Detect button press (HIGH → LOW)
  if (lastState == HIGH && currentState == LOW) {
    buttonPressTime = millis();
  }

  //  Detect button release (LOW → HIGH)
  if (lastState == LOW && currentState == HIGH) {

    unsigned long pressDuration = millis() - buttonPressTime;

    //  LONG PRESS → Turn LED OFF
    if (pressDuration > longPressTime) {
      ledOn = false;
      digitalWrite(ledPin, LOW);
      Serial.println("LONG PRESS → LED OFF");
      clickCount = 0;
    }

    //  SHORT PRESS handling
    else {
      unsigned long now = millis();

      // Check for double click
      if (now - lastReleaseTime < doubleClickTime) {
        clickCount++;

        if (clickCount == 2) {
          ledOn = true;
          digitalWrite(ledPin, HIGH);
          Serial.println("DOUBLE CLICK → LED ON");
          clickCount = 0;
        }
      } 
      else {
        clickCount = 1;
      }

      lastReleaseTime = now;
    }
  }

  // Update last state
  lastState = currentState;
}