# Robot Solves Sudoku On Paper

Sudoku is a great way to pass some time, especially on a long flight. However, we don’t think the airlines will let [Sanahm] board with his sudoku-solving robot. The basic machine looks like a 2D plotter made with aluminum extrusion, with the addition of a Raspberry Pi and a camera. The machine can read a sudoku puzzle, solve it, and then fill in the puzzle with a pen. Unlike humans, it should never need to erase its work.

The software uses OpenCV to process the camera data, find the grid, and the cells provided by the puzzle. TensorFlow recognizes the numbers. From there, it is all just math to solve the puzzle. Once solved, the plotter part of the robot takes over and fills in the blanks. After all that, this seems like the easy part.

# Handheld Sudoku (Assuming You Have Large Hands)

[Hari Waguna] wanted to build a computerized Sudoku game. Ordinarily, that wouldn’t be a big deal. You can buy one, of course, but what fun is that? There’s plenty of apps for phones, but again, not much of a challenge. If you want to preserve your hacker cred, you’d use a CPU board like an Arduino or a Raspberry Pi with an LCD screen, right? But if you want to grow your hacker cred, you’d follow [Hari’s] lead and use 81 seven-segment displays and a membrane keyboard.

Driving that many displays takes some doing (in this case shift registers). [Hari] uses some other tricks, like reading the keyboard using a single pin (and a resistor network). He’s made several videos about the project, including the one below.

# 7-segment Sudoku

[John Sarik] keeps cranking out new ideas for his digital Sudoku project. This time he’s using 7-segment displays for each digit. The game play works the same as the Nixie Tube version, but this makes things quite a bit easier to build. The board above is one of the nine modules that make up the game. They each use three shift registers to drive the nine 7-segment displays. With the help of five resistors all of the multiplexing is addressed via the serial input on those chips.

# Nixie Sudoku: A Look At The Hardware

We’re always happy to receive a tour of the guts that make things work. [John Sarik] posted several pictures and descriptions of the hardware that makes up his Nixie Sudoku build. The modular design uses professionally made circuit boards which greatly improve the durability of a large set of circuits such as this.

The design draws on good ideas from similar hardware. The Nixie Duo kit from Ogi Lumen allows tubes to be mounted on top of driver boards with cascading shift registers for control of up to 8 tubes. The ArduiNIX shield makes the high voltages needed for Nixies easy to control with an Arduino. No, [John] didn’t just order these kits and plug them into each other. He designed his own boards to suit his needs. Each driver board can control 9 tubes in a 3×3 grid, all on one PCB. His high voltage board can supply enough juice for the whole system which is tied together with a single Arduino board.

His writeup is quite interesting so do take a look. He also filmed a walk through video which we’ve embedded after the break. It clears up some questions, such as showing the use of a blinking decimal point to indicate the current cursor position.

# Nixie Sudoku

[John Sarik] asked himself why a project should only have a handful of Nixie tubes? Without a good answer to his query he went ahead and built this Sudoku game using 81 Nixie tubes. There’s not much of a description for his work but here’s how we think things go: The two knobs manipulate a cursor, one for rows and the other for columns, while the keypad is used to input your chosen number. The system is Arduino based and [John’s] linked to his code, schematic, and board layout files on Dropbox. He’s even written a recursive solver which can be seen in the video after the break. Would it be inappropriate to bring this to work and whip it out during some down time?