Electronic Dice

What you’ll make

Press a button and seven LEDs “roll,” then settle on a dice face from 1 to 6, chosen at random by your program.

What you need

• A Raspberry Pi Pico with its header pins already fitted (Pico H or Pico WH), a data-capable USB cable, and Thonny with MicroPython (Lesson 24)
• Two breadboards: a full-size one for the Pico and a half-size one for the dice face, plus jumper wires
• A printed copy of Raspberry Pi’s Pico pinout diagram
• 7 LEDs, 5 mm, all the same colour (red is easiest)
• 7 resistors, 220 Ω
• 1 pushbutton

Safety numbers for this build

Build it

1. Unplug the USB cable. Press the Pico into the full-size breadboard across the centre gap, with pin 1 in row 1.
2. Ground: jumper from row 8, column a (GND, pin 8) to the main board’s left − rail. Then jumper from that rail to both − rails on the half-size dice-face board.
3. Watch the GND pin: the LED pins are GP2 to GP8, which are physical pins 4, 5, 6, 7, then 9, 10 and 11. Pin 8 between them is GND, so don’t count straight down.
4. The dice face: each breadboard row half (a to e, or f to j) is one connection, so each LED needs rows of its own. Build the face on the half-size board using this table. “Rail” means the − rail along that side. The resistors bend to span two rows, and each short leg bends out to reach the rail.

5. Button: place it across the dice-face board’s centre gap at rows 18 to 20. GP16 is physical pin 21 on the Pico’s right side (row 20, column j). Jumper from main row 20 col j to face row 18 col a, and from face row 20 col j to the right rail. This uses diagonally opposite button legs.
6. Check every connection against the table and the pinout diagram, then plug in the USB cable.

Program it

from machine import Pin
import time, random

# LED positions:  TL   TR
#                 ML C MR
#                 BL   BR
pins = {"TL": 2, "TR": 3, "ML": 4, "C": 5, "MR": 6, "BL": 7, "BR": 8}
leds = {name: Pin(gp, Pin.OUT) for name, gp in pins.items()}
button = Pin(16, Pin.IN, Pin.PULL_UP)

faces = {
    1: ["C"],
    2: ["TL", "BR"],
    3: ["TL", "C", "BR"],
    4: ["TL", "TR", "BL", "BR"],
    5: ["TL", "TR", "C", "BL", "BR"],
    6: ["TL", "TR", "ML", "MR", "BL", "BR"],
}

def show(n):
    for name, led in leds.items():
        led.value(1 if name in faces[n] else 0)

show(1)
while True:
    if button.value() == 0:             # button pressed
        for i in range(12):             # quick "rolling" animation
            show(random.randint(1, 6))
            time.sleep(0.05 + i * 0.02)
        show(random.randint(1, 6))      # the final roll
        while button.value() == 0:      # wait for release
            time.sleep(0.01)
        time.sleep(0.05)                # let the contacts settle
    time.sleep(0.01)

Run it and press the button. To make it start by itself, choose File, Save as, then Raspberry Pi Pico, and name it main.py.

How it works

The faces table lists which LEDs make each dice face. random.randint(1, 6) picks a whole number from 1 to 6. The program waits for the button (which reads 0 when pressed, thanks to the pull-up), plays a short animation that slows down like a real die, shows the final number, then waits for you to let go, with a short pause so a bouncing contact (Lesson 11) can’t start a second roll.

Strictly, computers make pseudo-random numbers from a mathematical recipe, but for a dice game they are random enough.

It doesn’t work?

• One LED never lights: check its orientation and that its resistor goes to the right GP pin.
• The pattern looks wrong: two LEDs may be connected to swapped pins. Compare with the TL/TR/ML/C/MR/BL/BR list.
• The button does nothing: use diagonally opposite button legs, one to GP16 and one to the − rail.

For teachers and parents

Learn more

• Raspberry Pi: Pico documentation: official getting-started guides
• Project 6: Traffic Light Controller
• Back to Electronics School