Week 09: Input Devices

Group Assignment

• Probe an input device(s)'s analog levels and digital signals.
• Document your work on the group work page and reflect on your individual page what you learned.

Individual Assignment

• Measure something: add a sensor to a microcontroller board that you have designed and read it.

This week is all about Input devices…these are hardware used to provide data and control signals to a computer or information processing system like a keyboard, mouse scanner, camera, microphone, light switch or other such device.

Input devices that we come into contact like sensors and buttons can be (to name a few): Proximity, pressure, temperature and humidity, flow and level, alcohol, motion, colour, chemical, vibration, touch, infrared, gas, gyroscope, ultrasonic accelerometer (to measure the orientation of an object, its rate of change, including tap, shake, tilt and positioning), and so many more.

We were given a breadboard, wires and sensors

In a closed circuit measuring at ground the Voltage will be 0v. if the circuit is open then the voltage will be undefined. We connect basic breadboard circuit – and made a light flash when button pressed

We used multimeter to look at the voltage around the circuit

Then we went down to the lab and soldered pin connectors into both sides of a barduino and then put the barduino into the breadboard

Then I wrote a simple code analog read the pin

#define PIN 17

void setup() {
    pinMode (PIN, INPUT);
    // put your setup code here, to run once:
    Serial.begin(115200);
}

void loop() {
    int reading = analogRead(PIN);
    Serial.println(reading);
    // put your main code here, to run repeatedly:
}

and then ran it…and its giving off random numbers

so we ground it by connecting ground to pin 17 as can be seen in the image

so the circuit is running and when you push button on barduino now it closes circuit and that can be seen with the serial plotter

If we replace analog read with digital read the values change to 0 and 1

With new code it looks at the code and button not pressed reading is 1…..then button is pressed and the reading is 0, then 1, then when I hold it down the reading is 0 at every count until button is released, then reading 1 again – verifying the number of milliseconds the button has been pressed.

#define PIN 17
int prevReading = 0;
int reading = 0;
int timesPressed = 0;

void setup() {
    pinMode (PIN, INPUT);
    // put your setup code here, to run once:
    Serial.begin(115200);
}

void loop() {
    prevReading = reading;
    reading = digitalRead (PIN);

    if(reading == 0) {
        timesPressed = timesPressed + 1;
    }
    
    Serial.print("reading:");
    Serial.print(reading);
    Serial.print(" timesPressed:");
    Serial.println(timesPressed);

    delay(1);
}

Then in the next code, the serial port counts the number of times the button is pressed.

#define PIN 17
int prevReading = 0;
int reading = 0;
int timesPressed = 0;

void setup() {
    pinMode (PIN, INPUT);
    // put your setup code here, to run once:
    Serial.begin(115200);
}

void loop() {
    prevReading = reading;
    reading = digitalRead (PIN);

    if(prevReading == 1 && reading == 0) {
        timesPressed = timesPressed + 1;
    }
    
    Serial.print("reading:");
    Serial.print(reading);
    Serial.print(" timesPressed:");
    Serial.println(timesPressed);

    delay(1);
}

Moving on to a new input device – how a potentiometer works? It is like a variable resistor and it is essentially the technical name for a volume knob type input device – (an infinite one that keeps turning is called a rotary encoder)

One can set values for a potentiometer, so each movement or click corresponds to a particular output. It could be analog or digital meaning, like an analog volume not or perhaps a digital one with preset increments.

In the following video one can see the potentiometer control on the monitor reading as analog:

Now measuring the resistance of a light sensor when adding light the resistance decreases and when reducing light resistance is increased and this is the code

void setup() {
    pinMode (17, INPUT);
    // put your setup code here, to run once:
    Serial.begin(9600);
}

void loop() {
    int lecture = analogRead (17);
    Serial.println(lecture);
    delay(50);
}

Next we are going to measure a sensor individually so I am using the pir….

with the code below it showed motion detection but the light didn't change – it just stayed on

// Define the PIR pin
const int pirPin = 17;  

// Variable to store the PIR sensor status
int pirState = LOW;

void setup() {
    // Initialize the serial monitor at 9600 baud rate
    Serial.begin(9600);
    
    // Set the PIR sensor pin as input
    pinMode(pirPin, INPUT);
}

void loop() {
    // Read the state of the PIR sensor
    pirState = digitalRead(pirPin);

    // If the PIR sensor is triggered (motion detected)
    if (pirState == HIGH) {
        Serial.println("Motion Detected!");
    } else {
        Serial.println("No Motion");
    }

    // Delay for a short period (500ms) before the next reading
    delay(500);
}

So after updating the code A FEW times I rewired the LED not to take power directly and instead connected it to PIN 13. It is still not working yet but see updated wiring image

Finally got it to work but it seems slightly buggy and weird reaction times although conditions are not ideal for testing

This was the final code and screenshot. In the embedded video you will really have to squeeze your eyes on the right to see how the LED switches from OFF to ON, and at the same time do some gymnastics by squeezing your eyes left to notice that the serial monitor changed from No Motion detected to Motion Detected!

int pirPin = 17;   // PIR sensor output pin
int ledPin = 13;   // LED pin
int analogPin = A0; // Analog pin (change if needed)

void setup() {
    pinMode(pirPin, INPUT);
    pinMode(ledPin, OUTPUT);
    Serial.begin(9600); // For debugging
    delay(100); // 1 minute delay for sensor stabilization
}

void loop() {
    int pirValue = digitalRead(pirPin); // Read PIR sensor value
    int analogValue = analogRead(analogPin); // Read analog value

    if (pirValue == HIGH) {
        digitalWrite(ledPin, HIGH); // Turn LED on
        Serial.print("Motion Detected! Analog Value: ");
        Serial.println(analogValue); // Print analog value
        delay(100); // Small delay to avoid rapid triggering
    } else {
        digitalWrite(ledPin, LOW);  // Turn LED off
        Serial.print("No Motion. Analog Value: ");
        Serial.println(analogValue); // Print analog value
    }

    delay(50); // Small delay for loop stability
}