The 52-Card Shuffling Robot is designed to completely randomize a deck of playing cards in under 60 seconds. The robot is made up of three subsystems that work in sync: the input mechanism, the indexer drum, and the output mechanism. Each subsystem plays a critical role in ensuring a randomized shuffle and smooth card handling.

The first step in the shuffle process is dispensing one card at a time from an unshuffled deck. The input mechanism uses a stepper motor driving a rack and pinion system to grip and feed the bottom card from the deck into a set of double rollers. These rollers, powered by a 5V DC motor, propel each card into the indexer drum. Initially, I experimented with a servo motor to control the rack and pinion, but it was too slow for my time requirement. Switching to a stepper motor added complexity in wiring and programming but provided the necessary speed and control for reliable card dispensing.

The heart of the system is the round drum, which has 60 slots to hold the cards during the shuffle. After each card is inserted, the drum rotates to a random position to ensure the card is placed in a random slot. This rotation is powered by another stepper motor, and I integrated a gear ratio into the drum itself. The drum acts as both the indexer and the central axle for the card retrieval mechanism, which leads to the next subsystem.

The output mechanism is responsible for removing the shuffled cards from the indexer drum. Most designs I researched relied on gravity, allowing the cards to fall out naturally, but this wouldn't meet my 60-second time limit. I developed an active ejection system using a servo motor with a 3D-printed linkage inside the rotating drum. The servo pushes each card about half an inch out of the drum, and then a second set of rollers, powered by a 5V DC motor, pulls the card the rest of the way out for collection. I added finger cut outs in the side to make it easier to remove the cards.

The biggest hurdle was preventing multiple cards from sticking together and being dispensed simultaneously. I went through nearly 20 iterations of the dispensing mechanism, tweaking the dimensions and design of the rack and pinion system to achieve consistent one-card dispensing.

Removing cards from the indexer drum proved to be a major challenge, especially with the time limit I imposed. Relying on gravity alone wouldn't be fast or consistent enough, so I had to design a system that actively pushed cards out of the drum. I tested various solutions, including pulling and pushing mechanisms, but many either jammed or failed to maintain the necessary speed. I finally settled on a hybrid solution: the servo motor pushes the cards slightly out of the drum, and a second set of rollers quickly pulls them out. This combination ensured the cards were ejected reliably and within the time constraint.

During initial tests, I found that the system’s power consumption was causing the Arduino to brownout and restart when motors were activated. After some troubleshooting, I determined that the voltage was dropping to around 4V, which was too low for the Arduino. I opted to use two separate battery packs—one for the control circuits and one for the motors. This separation prevented the voltage drop from affecting the Arduino’s operation. I could have used capacitors to smooth the voltage, but using separate power supplies was a simpler and more reliable solution for this project.

The software aspect of the project was straightforward but essential for ensuring a truly randomized shuffle. The system needed to control two stepper motors, two DC motors, one servo motor, and a set of indicator LEDs. Each motor had its own function in the program, which allowed me to sequence the shuffle operations.

To generate randomness, I used an analog reading from an empty pin on the Arduino to seed the random function. This method ensured that the shuffle sequence was different every time. I then used an array of 52 integers, representing card positions, and performed 60 swaps between random pairs of cards. This method achieved a well-randomized deck without adding significant time to the process.

This project was a valuable learning experience, particularly in how to approach complex problems without a clear solution. By iterating quickly through different designs and prototypes, I was able to identify issues early and refine my solutions. Revisiting my original design requirements throughout the process helped ensure that my final design met the 60-second time constraint while still functioning reliably.

One key takeaway is the importance of managing complexity, both in mechanical design and in electronics. By organizing the electronics in a clean and accessible way, I avoided the mess of exposed wires while still allowing easy debugging. Overall, this project improved my ability to prototype, test, and refine a system to meet specific goals.