Introduction
Related Projects and Inspiration
Description
Shuffling Method
Software
Design
Video
Milestone 1
Milestone 2
Milestone 3
Future Improvements

Chenqi Zhu

•

Advait Vartak

•

Siddhi Patil

Published December 16, 2024 © GPL3+

Card Shuffler

A card shuffler that automatically shuffles your cards!

IntermediateFull instructions provided502

Things used in this project

Hardware components

Espressif ESP32

DC motor (generic)

DRV8833 DC/STEPPER MOTOR DRIVER

SG90 Micro-servo motor

Software apps and online services

Autodesk Fusion

Hand tools and fabrication machines

3D Printer (generic)

Story

Introduction

Shuffling cards by hand can be tedious as the dealer may be asked to do it dozens of times in the span of a few hours and perilous as your stingy friend who lost 20 dollars at Texas Holdem may get mad at you for always giving them the worst hand, accuse you of cheating and ruin your friendship. If only there’s a simple-to-build machine that shuffles the cards for you and can guarantee the randomness of the shuffled deck, maybe your fragile friendship can still be preserved. We intend to present to you such a miraculous machine. Our Card Shuffler only consists of two DC motors and one servo motor with all other parts being 3D printed. It would shuffle your cards by randomly dividing the deck into two and recombining them. Our design protects the fairness of card shuffling while being easy to use.

Most card shufflers on the market use similar designs, one where the user splits the deck into two, inserts it into the machine, and the machine interlaces them together. There have even been hand-operated shufflers that do the same, like this one by Josh-3D. It also includes a drawer-like system to remove the shuffled deck, which we also implement in our design.

Description

Shuffling Method

Consider a deck of unshuffled cards, the device follows the rule of riffle shuffle where it splits the deck into two packets and then combines them. For each card, whether it goes to packet A or packet B is chosen at random. After all cards have been allocated, packet B is stacked on top of packet A. Repeat this process multiple times will give out a deck of cards that is fully shuffled.

A pile shuffle is a shuffling method where you distribute a deck of cards into a number of piles, and then combine all of the piles into one shuffled deck. Our robot implements a method similar to this, where it places cards either to the left or to the right, creating a left deck and right deck. At the end it places the right deck on top of the left deck, creating a single shuffled deck. And while a normal pile shuffle would alternate between left and right, our robot picks randomly, introducing more chaos into the shuffle.

Software

The software is simple and easy to use. The servo motor will reset to default position after the shuffler starts running. Pressing A on the keyboard will start the shuffling. After the shuffling is done, press S to stop the DC motors and release the servo motor.

Design

Starting with a top card holder that contains all the cards to be shuffled. There are two motors under the card holder. With the software controlling the motors, the cards are dealt either from the left or right side of the card holder. The cards dealt on the left side are caught by a wing shaped structure and slide into the bottom card holder while the cards on the right are caught by a hook-shaped stopper and stack on the right wing. After all cards have been dealt from the top card holder, the hook on the right side would release all the cards on the right wing into the bottom card holder. The bottom card holder would subsequently contain all the cards after one shuffle.

The bottom card holder can then be pulled out like a drawer, and the deck can be taken out.

Video

Milestone 1

In Milestone 1 we aimed to come up with an idea and general design of our project. Our initial design included a single wheel at the top of the deck to be shuffled. It would act as a weight on the top of the cards and would lower as the deck got smaller. The cards would accumulate in two different platforms, one of them being able to open like a trap door. After all the cards have been divided, that trap door would open, letting the two decks merge.

Milestone 2

In Milestone 2, we tried to create a working prototype and refine the design further. We decided to place the bottom so that they would not need to move, and added two wheels to make sure the cards moved out of the holder completely.

We built the top part of the machine as a prototype, testing our design’s ability to move cards out of the holder.

We found that it worked for the most part, but the construction was too flimsy, the motors would bend outwards and not touch the cards. It needed to be manually held together for it to work.

Milestone 3

In Milestone 3, we finished building the robot, refining our prototype for the top, and building out the bottom. The flimsiness of the top was fixed by adding metal rods to connect the top and bottom card holders. The metal rods held the motors in place. We noticed that cards were not falling straight but leaning to the side when exiting the card holder, so we added walls to keep them aligned.

We also changed the design so both of the sloped wings are on the same level. And instead of a trapdoor, we added a hook-shaped stopper to stop the decks from combining immediately. We went through many iterations of the bottom card holder, increasing both width and depth so that cards wouldn’t get stuck in it.

Future Improvements

The structure can be made more stable by adding bolts to secure the motors to the top card with bolts, and adding supports for the wings on either side.
Cards are still getting stuck when exiting the top card holder. A potential solution could include increasing the voltage the motors are run at so cards exit the holder faster.
Checking if all the cards have left the top card holder is a little awkward. This can be solved by making it so that when the weight reaches the bottom of the card holder, it completes a circuit and the robot automatically knows to combine both the decks.
Increasing the speed of shuffling to improve the overall practicality of the Card Shuffler in a real world situation

Shuffling Code

#include <Arduino.h>

#define MOT_A1_PIN 19
#define MOT_A2_PIN 18

#define MOT_B1_PIN 23
#define MOT_B2_PIN 22

#define SERVO_PIN 13

void servoWrite(int angle) {
  int width = map(angle, 0, 180, 500, 2600);
  digitalWrite(SERVO_PIN, HIGH);
  delayMicroseconds(width);
  digitalWrite(SERVO_PIN, LOW);
  delayMicroseconds(20000 - width);
}


void setup(void)
{
  // Set motor A control pins to OUTPUT
  pinMode(MOT_A1_PIN, OUTPUT);
  pinMode(MOT_A2_PIN, OUTPUT);
  pinMode(MOT_B1_PIN, OUTPUT);
  pinMode(MOT_B2_PIN, OUTPUT);

  pinMode(SERVO_PIN, OUTPUT);

  // Turn off motor A and B initially
  digitalWrite(MOT_A1_PIN, LOW);
  digitalWrite(MOT_A2_PIN, LOW);
  digitalWrite(MOT_B1_PIN, LOW);
  digitalWrite(MOT_B2_PIN, LOW);

  digitalWrite(SERVO_PIN, LOW);

  for (int j = 0; j < 10; j++){
    servoWrite(95);
    delay(15);
  }
  Serial.begin(9600);

  Serial.println("===========SHUFFLE BOT===========");
  Serial.println("PRESS A TO START");
  Serial.println("PRESS S TO STOP");
}

void loop(void)
{
  char instr = Serial.read();

  if (instr == 'a') {  
    for (int j = 0; j < 10; j++){
      servoWrite(95);
      delay(15);
    }

    while(instr!= 's') {
      instr = Serial.read();
      digitalWrite(MOT_A1_PIN, LOW);
      digitalWrite(MOT_A2_PIN, LOW);
      digitalWrite(MOT_B1_PIN, LOW);
      digitalWrite(MOT_B2_PIN, LOW);
      // delay(10);
      int dir = random(2);  

      if (dir == 0) {
        digitalWrite(MOT_A1_PIN, LOW);
        digitalWrite(MOT_A2_PIN, HIGH);
      }
      else {
        digitalWrite(MOT_B1_PIN, HIGH);
        digitalWrite(MOT_B2_PIN, LOW);
      }

      delay(1000);
    }
    digitalWrite(MOT_A1_PIN, LOW);
    digitalWrite(MOT_A2_PIN, LOW);
    digitalWrite(MOT_B1_PIN, LOW);
    digitalWrite(MOT_B2_PIN, LOW);
    Serial.println("\nSHUFFLING FINISHED\n");
    Serial.println("PRESS A TO START");
    Serial.println("PRESS S TO STOP");

    for (int j = 0; j < 10; j++){
      servoWrite(0);
      delay(15);
    }
    delay(100);
  }

  delay(10);
}

Credits

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Card Shuffler

Card Shuffler

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Related Projects and Inspiration

Description

Shuffling Method

Software

Design

Video

Milestone 1

Milestone 2

Milestone 3

Future Improvements

Code

Shuffling Code

Credits

Chenqi Zhu

Advait Vartak

Siddhi Patil

Comments

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