Mission 17 · Stage 2

Electronic Dice

random() triggered by a button

Roll a random number 1–6 on a 7-segment display when you press a button.

Pin connections

Part 1		Part 2
Arduino pin 2	→	Roll button pin 1
Roll button pin 2	→	Arduino GND
Arduino pin 3	→	7-segment display seg A
Arduino pin 4	→	7-segment display seg B
Arduino pin 5	→	7-segment display seg C
Arduino pin 6	→	7-segment display seg D
Arduino pin 7	→	7-segment display seg E
Arduino pin 8	→	7-segment display seg F
Arduino pin 9	→	7-segment display seg G
7-segment display COM	→	Arduino GND

See it

Let's roll a dice with code!

Press the button and a surprise number 1 to 6 pops up — just like a real die.

Board games and game apps use random numbers so you can never guess what comes next.

The story

The problem

We want a new surprise number every time, not the same number again and again.

Think of it like

Like shaking a real die — you can never tell what face will land up.

Meet the parts

It picks a random number and shows it.

Arduino

The brain

Loading part…

Press it to roll a new number.

Roll button

The roll button

Loading part…

It lights up little bars to show a number 1 to 6.

7-segment display

The number screen

Loading part…

How it works

Wait for a press

We only roll when you press the button.

if (digitalRead(BUTTON_PIN) == LOW)

Pick a surprise number

random(1, 7) gives a number from 1 to 6 — perfect for a die.

int roll = random(1, 7);

Light up the number

showDigit turns the right bars on and off to draw your number.

showDigit(roll);

Then loop back to step 1

Build the circuit

Follow these steps in order. Match the wires to the colors shown.

1
Place Arduino
Place the Arduino (uno) on the breadboard.
Arduino placed — ready to build!
Loading part…
2
Place Roll button
Place the Roll button (btn1) on the breadboard.
Loading part…
3
Place 7-segment display
Place the 7-segment display (seg1) on the breadboard.
Loading part…
4
Connect Arduino pin 2 to Roll button (btn1) 1.l
Connect Arduino pin 2 to Roll button (btn1) 1.l.
5
Connect Roll button (btn1) 2.l to Arduino GND
Connect Roll button (btn1) 2.l to Arduino GND.
6
Connect Arduino pin 3 to 7-segment display (seg1) anode (+)
Connect Arduino pin 3 to 7-segment display (seg1) anode (+).
7
Connect Arduino pin 4 to 7-segment display (seg1) B
Connect Arduino pin 4 to 7-segment display (seg1) B.
8
Connect Arduino pin 5 to 7-segment display (seg1) cathode (-)
Connect Arduino pin 5 to 7-segment display (seg1) cathode (-).
9
Connect Arduino pin 6 to 7-segment display (seg1) D
Connect Arduino pin 6 to 7-segment display (seg1) D.
10
Connect Arduino pin 7 to 7-segment display (seg1) E
Connect Arduino pin 7 to 7-segment display (seg1) E.
11
Connect Arduino pin 8 to 7-segment display (seg1) F
Connect Arduino pin 8 to 7-segment display (seg1) F.
12
Connect Arduino pin 9 to 7-segment display (seg1) G
Connect Arduino pin 9 to 7-segment display (seg1) G.
13
Connect 7-segment display (seg1) COM.2 to Arduino GND
Connect 7-segment display (seg1) COM.2 to Arduino GND.

Try it

Press the button again and again — the number should keep changing.
No fair guessing — random() decides each roll!

Peek at code

Number shapes

const uint8_t DIGITS[7] = {
  0b0000000,
  0b0000110,
  0b1011011,
  0b1001111,
  0b1100110,
  0b1101101,
  0b1111101,
};

Each number has a pattern that says which bars turn on to draw it.

showDigit()

void showDigit(int digit) {
  uint8_t pattern = DIGITS[digit];
  for (int seg = 0; seg < 7; seg++) {
    digitalWrite(SEG_A + seg, (pattern >> seg) & 1);
  }
}

It steps through the bars and turns each one on or off from the pattern.

Roll on a press

void loop() {
  if (digitalRead(BUTTON_PIN) == LOW) {
    int roll = random(1, 7);
    showDigit(roll);
    while (digitalRead(BUTTON_PIN) == LOW) {
      delay(10);
    }
    delay(200);
  }
  delay(20);
}

The button picks a random number, then showDigit() shows it until your next roll.

Show full sketch (electronic-dice.ino)

const int BUTTON_PIN = 2;
const int SEG_A = 3;
const uint8_t DIGITS[7] = {
  0b0000000,
  0b0000110,
  0b1011011,
  0b1001111,
  0b1100110,
  0b1101101,
  0b1111101,
};
void showDigit(int digit) {
  uint8_t pattern = DIGITS[digit];
  for (int seg = 0; seg < 7; seg++) {
    digitalWrite(SEG_A + seg, (pattern >> seg) & 1);
  }
}
void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  for (int i = 0; i < 7; i++) {
    pinMode(SEG_A + i, OUTPUT);
  }
  showDigit(1);
  randomSeed(analogRead(0));
}
void loop() {
  if (digitalRead(BUTTON_PIN) == LOW) {
    int roll = random(1, 7);
    showDigit(roll);
    while (digitalRead(BUTTON_PIN) == LOW) {
      delay(10);
    }
    delay(200);
  }
  delay(20);
}

Quick quiz

Q1. Where does work that repeats go?

A. loop() ✓
B. setup()
C. pinMode only

Why: Yes! loop() runs again and again.

Q2. What numbers can random(1, 7) give?

A. 1 up to 6 ✓
B. 1 up to 7
C. Always 3

Why: Yes! 7 is not included, so you get the six die faces.

Code lab — try on your own

Add a note (comment) on the randomSeed line that says it makes different rolls each run.
Hint: That's line 24 in setup().
Hold the number longer — change delay(200) to delay(400).
Hint: That's line 33 in loop().

Code walkthrough

A line-by-line tour of the sketch — the same steps as in Robot Gurukul Studio.

Program overview

Big idea

Every Arduino program has a top part, a setup() part that runs once, and a loop() part that runs again and again.

In this project

Press the button and a number from 1 to 6 shows up, just like rolling a die.

Tip

Read from the top to the bottom. Tap any word or line if you need help!

const int BUTTON_PIN = 2;
const int SEG_A = 3;
const uint8_t DIGITS[7] = {
  0b0000000,
  0b0000110,
  0b1011011,
  0b1001111,
  0b1100110,
  0b1101101,
  0b1111101,
};
void showDigit(int digit) {
  uint8_t pattern = DIGITS[digit];
  for (int seg = 0; seg < 7; seg++) {
    digitalWrite(SEG_A + seg, (pattern >> seg) & 1);
  }
}

setup()

Big idea

setup() runs one time when the board turns on.

In this project

It gets the button and the number display ready, shows a 1, and mixes up the randomness.

Why here

Things we do only once go inside setup().

void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  for (int i = 0; i < 7; i++) {
    pinMode(SEG_A + i, OUTPUT);
  }
  showDigit(1);
  randomSeed(analogRead(0));
}

loop()

Big idea

loop() runs again and again, forever.

In this project

It waits for a button press, then rolls a new number.

Why here

Things that repeat go inside loop().

void loop() {
  if (digitalRead(BUTTON_PIN) == LOW) {
    int roll = random(1, 7);
    showDigit(roll);
    while (digitalRead(BUTTON_PIN) == LOW) {
      delay(10);
    }
    delay(200);
  }
  delay(20);
}

Try this: Change a number inside loop(), then press Run to see what happens.

pinMode

Big idea

pinMode tells a pin if it will listen or push power out.

In this project

It sets the button pin to listen and the display pins to push power out.

Why here

It goes in setup() because we only set it once.

  pinMode(BUTTON_PIN, INPUT_PULLUP);

digitalWrite

Big idea

digitalWrite turns a pin ON or OFF.

In this project

It turns each little bar of the display on or off to draw the number.

Why here

It is used inside showDigit() to paint the number.

    digitalWrite(SEG_A + seg, (pattern >> seg) & 1);

digitalRead

Big idea

digitalRead checks if a pin is ON or OFF.

In this project

It checks if you pressed the roll button.

Why here

It goes in loop() so we can react to your press.

  if (digitalRead(BUTTON_PIN) == LOW) {

analogRead

Big idea

analogRead reads a number from a pin, from 0 up to 1023.

In this project

It reads a wiggly number from an empty pin to mix up the randomness.

Why here

In setup() so the rolls are different each time.

  randomSeed(analogRead(0));

delay

Big idea

delay means wait. Nothing else happens while it waits.

In this project

A short wait holds the rolled number for a moment.

Why here

Right after a roll, before checking the button again.

      delay(10);

random

Big idea

random picks a surprise number for you.

In this project

It picks a number from 1 to 6 — your dice roll.

Why here

In loop() when you press the button.

    int roll = random(1, 7);

← 16. Quiz Buzzer 18. Simon Says →