PCOM – Week 02

Digital Input & Output with an Arduino

Arduino Uno connected to pushbutton and LED

and adding two LEDs (Red, Yellow)…

void setup() {
  pinMode(2, INPUT);    // set the pushbutton pin to be an input
  pinMode(3, OUTPUT);   // set the yellow LED pin to be an output
  pinMode(4, OUTPUT);   // set the red LED pin to be an output
}

void loop() {
   // read the pushbutton input:
   if (digitalRead(2) == HIGH) {
     // if the pushbutton is closed:
     digitalWrite(3, HIGH);    // turn on the yellow LED
     digitalWrite(4, LOW);     // turn off the red LED
   }
   else {
     // if the switch is open:
     digitalWrite(3, LOW);     // turn off the yellow LED
     digitalWrite(4, HIGH);    // turn on the red LED
   }
 }

Lab: Analog In with an Arduino

Add a Potentiometer and LED

const int ledPin = 9;       // pin that the LED is attached to
int analogValue = 0;        // value read from the pot
int brightness = 0;         // PWM pin that the LED is on.
void setup(){

  // initialize serial communications at 9600 bps:
    Serial.begin(9600);
    // declare the led pin as an output:
    pinMode(ledPin, OUTPUT);
}

void loop() {
    analogValue = analogRead(A0);    // read the pot value
    brightness = analogValue /4;       //divide by 4 to fit in a byte
    analogWrite(ledPin, brightness);   // PWM the LED with the brightness value
    Serial.println(brightness);        // print the brightness value back to the serial monitor
}

 a potentiometer connected to analog in 0 of an Arduino and an LED connected to digital pin 9.

const int pinNumber = 9;       // pin that the LED is attached to
int analogValue = 0;        // value read from the pot
int frequency = 0;         // PWM pin that the LED is on.
void setup(){
  // initialize serial communications at 9600 bps:
    Serial.begin(9600);
    // declare the led pin as an output:
    pinMode(pinNumber, OUTPUT);
}

void loop() {
    analogValue = analogRead(A0);      // read the pot value
    frequency = (analogValue /4) * 10; // divide by 4 to fit in a byte, multiply by 10 for a good tonal range
    tone(pinNumber, frequency);        // make a changing tone on the speaker
         
}

replacing the LED with a speaker that will play a changing tone.

Gear motor + potentiometer + pushbutton control

To further, I wanted to control DC motor by adjusting the intensity with a potentiometer on the pushbutton. So in this page, ‘Lab: Using a Transistor to Control High Current Loads with an Arduino’s Figure 22, I experimented with motor before connecting to my labtop and arduino first. It looks like working well.

Things you need

• microcontroller
• jumper wire/ aligator clips
• gear motor
• potentiometer
• breadboard
• 1N400x power diode
• TIP120 transistor

an Arduino connected to a potentiometer, a transistor, a DC motor, and a DC jack. A transistor is connected to Digital Pin 9. A DC motor connects to the transistor and a DC jack. The DC jack connects its positive wire to the first wire of the DC motor. The negative wire of the DC jack connects to ground. The second wire of the DC motor connects to the collector of the transistor. A 1N400x diode’s cathode is connected to the collector, and its anode is connected to ground.

In this circuit, I added one pushbutton here.

Now, connect all together, Potentiometer + pushbutton + gear motor(with a pinwheel) In other words, control a gear motor by adjusting the intensity with a potentiometer on the pushbutton’s on & off.

• on= push (which is ‘move’ the motor)
• off = not push (which is ‘stop’ the motor)

const int transistorPin = 9;
const int button = 2;
int buttonValue = 0;
int Pot = A0;


void setup() {
  Serial.begin(9600);
  pinMode(transistorPin, OUTPUT);
  pinMode(button, INPUT);
  pinMode(Pot, INPUT);
}

void loop() {
  buttonValue = digitalRead(button);

  if (buttonValue == HIGH) {
    int sensorValue = analogRead(A0);
    // map the sensor value to a range from 0 - 255:
    int outputValue = map(sensorValue, 0, 1023, 0, 255);
    analogWrite(transistorPin, outputValue);
  } else {
    analogWrite(transistorPin, 0);
  }

}

Problem & Questions

– Why the pushbutton did not work? not a complete circuit? or code error in code sketch?

– why a 1N400x power diode needed?

– alternatives? motor drive or H-bridge??