Introduction: Electronic Connect Four (arduino)


Kelly Bodeman -

Jack Whelan -

(For more questions contact us at our emails above)

Here is a link of a youtube video of our project: Connect Four Video

California Maritime Academy (Marine Engineering Technology)

Professor Chang-Siu (ET370 Electronics)

The Idea:

Connect Four is a two-player game typically consisting of a 7 x 6 board where players physically drop their chips into their desired slot. The goal of the game is to get four of your color in a row whether it be vertically, horizontally, or diagonally. Instead of physically dropping the chips into slots there are buttons that correspond to their nearest row. When the button is pressed the board will play an animation of a ball dropping. The color/player changes from blue and red every time a ball is dropped. The most challenging part of this project is detecting a win. The solution to this was to scan for a win every time a ball is placed, and at the location, it is placed. From that location, it scans in every possible direction (horizontal, vertical, and both diagonal directions). To keep things simple it only scans the nearest line, which also makes the win scan a little faster. Another thing to detect would be a tie, to detect a tie we could set a counter for how many plays there have been, and when that limit is reached it displays a tie.


Below is the list of materials used for this project:

  1. Neo Pixel LEDs
  2. Arcade Buttons
  3. ping pong balls
  4. Arduino Uno
  5. Power Supply (Arduino) (9V 2.5A)
  6. Wires
  7. circuit boards
  8. breadboard
  9. PLC 3D Printing Material
  10. Acrylic Sheets
  11. Various screws
  12. Aluminum bar for stand

Step 1: Project Functionality


Above is the basic functionality of how the game will theoretically work. This game is designed to play identical to how one would play the real connect four. For example, if you plug the game in it won't do anything until a button is pressed. Each button corresponds to the column it is below, which can be seen in the diagram. Once a button is pressed it will animate a puck dropping and it will place it in its corresponding place. However, if a column is completely full you will not be able to drop another puck. This continues until the program detects that any series of the lights have a four in a row it animates a win by progressively lighting up the whole board with whatever color won. If there is no winner and the board is completely full then you can reset the game. To restart the game at any time the side button can be pressed.

Step 2: Circuit Diagram


There are 8 buttons on this project. 7 of the buttons correspond to its nearest row. Then the 8th button is a reset button. Since we used an Arduino there were not enough input pins on the board to have each one have its own connection, so the solution to this was to use resistors at different values connected in parallel. This uses the concept of a voltage divider. Different voltages will be sensed for in the code and then show which resistor/button was pressed. The power source can be anything from 7-12 V. There is a voltage regulator that steps down the voltage to 5v to power the LED matrix, and also supplies the Arduino with whatever the incoming voltage is.

Power Consumption:

As for power consumption all of these components run at 5 V. Each neo-pixel has a max consumption of 60 mA, with 42 of these, and the Arduino itself has a max power usage of 50 mA. With all of this taken into account, we would need a 13 W power supply, at 5 V.

Step 3: Code Logic State Machine

Above is the logic diagram which shows the basic concept of our code. When the game is plugged into the power source the game automatically starts which is in the “initialize game” state. This state also clears and sets the data. Then it goes straight to the “button sensing” state. The player colors are preset so all the player needs to do is press a button. Once a button is pressed it senses which column to drop the ball. Next, the code runs through the ball drop animation and then scans for a win. These steps repeat until it senses there are four of one color in a row, which would then go to the “win animation” state. Also at any time, the game can be reset with the reset button as shown above in the logic diagram.

There are still some flaws within our code. One of those is we need a tied state because it is possible to have no winner. Therefore, another state should be made since it is possible for that to happen. There are several other features that could be added but those will just be extra animations/states or fun improvements to this project.

The code is broken up into these four main states:

State 1, Button Sensing

State 2, Ball Drop Animation

State 3, Win Detect

State 4, Win Animation

Step 4: Code

Button Sensing:

  if ( voltage1 > 4.4 && voltage1 < 4.9 && buttonblock == 0 && overload[0] == 0) {
    Serial.println ("button 1");
    buttonstate[0] = 1;
    buttonblock = 1;
      if (buttonstateprev1 == 0 && buttonstate[0] == 1) {
        State = 2;
        x = 0;

As stated before the buttons use a voltage divider and then sense the voltage to know which button was pressed. We first found what voltage each button was sensing when pressed then but a range into the code so it would know whether the 1st or 2nd or 3rd button was pressed. The buttons are broken into 3 branches since we did not have enough variation in the voltages which so we broke them into separate input in the code which caused no issue.

Ball Drop Animation:

    case 2: //animation
      Serial.println("in State 2 (animation)");
      Serial.print("anistate = ");
      switch (anistate) {
        case 1: //checking for overload and adjusting if it sees anything
          if (y[x] <= 0) {
            y[x] = 0;
            Serial.print("row overload");
            overload[x] = 1;
            anistate = 2;
          else {
            anistate = 2;

The ball drop animation was pretty simple. All it does is check the hight of the active row and animates the ball until it reaches that height. After that is sets the new color, sets the height of the active row, and sends it to the next state. The actual animation part of this code just draws a pixel on the matrix, shows it, then deletes that drawn pixel and moves to the next one below and shows that. This repeats until it reaches the height of that row.

Win Detect:

    case 3: //win detect
      switch (winstate) {
        case 0: //setting led states
          Serial.println("winstate 0");
          scanX = 0;
          win = 0;
          scanY = y[x] + 1;
          winstate = 1;

        case 1: // horizontal scan
          if ( BoardMatrixState[scanX][scanY] == BoardMatrixState[x][Y]) {
          else {
            win = 0;
          if (win >= 4 ) {
            Serial.println("someone won horizontal");
            State = 4; //win detected
          if (scanX >= 6) {
            win = 0;
            scanY = 0;
            scanX = x;
            winstate = 2; //move to vertical scan

There are 4 win cases: horizontal, vertical, diagonal up/down. Each different win scenario has its own case. To make the scan easier we created a matrix of arrays to help sense the location of LEDs of where the ball was dropped. When looking at the code we designated the Blue = 1 & Red = 2.

Win Animation:

    case 4: //Win Animation
      // 1 is blue, 2 is red, 0 is off
      if (BoardMatrixState[x][Y] == 2) {
        colorWipe(strip.Color(255,   0,   0), 100);
      else {
        colorWipe(strip.Color(0,   0,   255), 100);
      State = 5; 
    case 5:
      if (buttonstateprev1 == 0 && buttonstate[7] == 1) {
        digitalWrite(Reset, LOW); //resets arduino

The win animation starts after a win is detected. The code runs through a simple color swipe which displays the winner color across the board. After this, you can reset the game but pressing the reset button on the side of the board.

Step 5: CAD Drawing

First off we started making a 3D CAD drawing of the whole game, theoretically, we wanted the final product to be similar. We wanted to keep the same design as a normal connect four board but we wanted to make it a little different which is why we used the ping pong balls to cover the LED, to make the game pop out more. Since we could not buy a connect four board that would be big for our design, we custom made the board by 3D printing it into 4 parts. Above are the 2 designs we thought would be ideal for the game, after some debate we decided to use the left version.

Using CAD was very important to help visualize how the project would work. Any complex parts were designed using Autodesk Inventor and then 3D printed. Any renderings depicted were made using Blender

Step 6: 3D Design & Dimension

Many of the dimensions for this project could be changed depending on how big you want the board to be. The only constants to keep in mind are the sizes of the ping pong balls which are 40mm in diameter. This is a standard for all ping pong balls. Any 3D printed dimensions can be found in the CAD files.

The dimension for our board as following:

Length: 13 ‘’

Width: 1 ‘’

Height: 11.2’’

Ping pong ball slot diameter: 40mm

LED slot diameter: 10mm

Screw diameter: .25”

Step 7: Initial Testing

Throughout this project we did some testing before assembling the whole project. Te first thing you should testing while constructing this project is after soldering all 42 LEDs together test them to check all your solder joints are working. After that we tested various parts:

  • 3D printed a section of the board:

After printing a section of the board, we realized we needed to edit the dimensions for certain parts since they did not fit as well as needed. We added some neo-pixels on the back and soldered some wires to later test how bright we want the lights to be when we put the ping pong balls over the top. Make sure to test your dimension before printing the whole board.

  • Drill size for the ping pong balls:

After soldering all the LEDs together we tested to see how big we need to drill the ping pong ball to cover the LED

  • Coded the algorithm to drop the balls in each column:

With this testing, we can transfer the knowledge to be able to code with neo-pixels, and we could potentially use parts of this code in the final In this testing, we learned how to use parts of the neo-pixel library, and how to use RGB variables (which will be very useful)

Step 8: Assembly


Almost all the parts in this project were custom made. Most were made using a 3D printer using PLA filament. The acrylic was cut using a table saw and drilled with a drill press. All lights and wiring connections were soldered. The Arduino is attached to the back using screws into the acrylic. The stand was made by hammering metal around a template made out of wood. Even the matrix was soldered together piece by piece and then attached to the back in the wiring grooves.

After printing all the board pieces and attaching them all together and the LED matrix attached to the back, the rest of the game could be assembled. First, the ping pong balls were drilled and then glued over the LED, then the brightness of the LED was adjusted to be seen through the ping pong ball. The construction of this project was a lot of fun and we were able to use creative ideas. There is still room for improvement.

Step 9: Conclusion & Improvements


The main concept of this game is to detect four LEDs of the same color in a row whether it be horizontal, vertical, or diagonal. We custom made an LED matrix for the board that was 3D printed. Though throughout the project we had to make some tweaks in our circuit diagram with the buttons and adjust the dimension of the 3D printed board to fit the ping pong balls. The buttons were a little tricky since we were using a voltage divider and then detecting the voltage across each button to differentiate them. To limit the overlap of the button we made three branches to different sensing pins on the Arduino which can be seen in the circuit diagram. This project was very code-heavy from the animation to the win-detect function. Although the construction did take a while, it was definitely the code that was the most complicated. A good understanding of state switching cases was essential to our project. Even knowing how and where to troubleshoot problems in the code was crucial. There were many cases we needed to troubleshoot the code to figure out where the problem was. After that, we were able to complete the whole project and it works fantastically.


Other win animations:
We could have the player who won four in a row flash with the four that won. Another animation would have the balls seem like they're all drop down like in a normal Connect Four game when clearing the game.

Select Player color:

A fun improvement would be to have the player be able to select the color they want to play with instead of having it pre-set.