Mechanical Checkers

Peter FrandinaRaymond PoudrierChristopher Rouland

Agenda

Project objective Interface design and layout Initialization and startup Hardware components Software components Testing / Integration Remaining Issues Questions

Project Objective

-To Achieve a Physical Checkers Game Experience Against a Computer Opponent

Physical game board with tangible pieces Enjoyable for players of variable skill Computer plays using a microcontroller and

magnets hidden below the playing surface Piece placement detected by embedded photocells

Game-play

Follows Traditional English Draughts If one or more jumps exist, one must be taken

User is responsible for ‘kinging’ pieces at appropriate times

The user is responsible for removing all pieces jumped during his or her turn

Computer is responsible for removing all pieces jumped during its turn

Exterior Physical Layout

Game Board24”x24”x10”

Squares2” green/white in color24 black squares along perimeter for captured pieces

PiecesRed/white in color

Error

IllegalMove

Performed

WhiteTurn

Move inProgress

RedTurn

Takeback Reset Start/Resume

Draw

Difficulty

HardEasy Med

Draw

User Interface

5 Push-Button Switches Reset, Start/Resume, Take Back, Draw, Difficulty

9 LEDs 2 Turn Indicators, Move in Progress, Illegal Move

Performed, Error, Draw, 3 for difficulty level

Initialization

Initially, the user is required to set up the checker board by placing all checkers in their appropriate starting locations

User selects difficulty setting User presses the “Start / Resume” button

All checker locations are verified by checking photocell values. If board is setup correctly, motors will move to starting locations, and game will begin

Otherwise, error light will be illuminated

Error Recovery

Errors Illegal jump/move Checkers are placed in improper locations during the

user’s turn

Recovery The error light is illuminated, at which point all checkers

have to be replaced to last known valid location The user then presses the “Start / Resume” button, and

all checker locations are verified via the photocell values

If board is in last valid state, the game will resume

Photocell Board Placement

Error

IllegalMove

Performed

WhiteTurn

Move inProgress

RedTurn

Takeback Reset Draw

Difficulty

HardEasy Med

Draw

Start/Resume

56 Photocells Used 32 Playing surface 24 Removed checker

locations 5mm wide x 4mm high x 2mm

thick Light Resistance = 5k Dark Resistance = 500k Mounted flush with the board

surface Centered in each square

Microcontroller Module

CSM12D module Uses Freescale MC9S12DT256

5V power requirement 16bit processor 256K byte Flash EEPROM 4K byte EEPROM 12.0K byte RAM

Microcontroller I/O Scheme

61 Inputs (Photocells, switches) 19 Outputs (LEDs, motors) Not enough on breakout header of CSM12D

I/O expander via I2C bus (Inter-Integrated Circuit) 4x 16 bit I/O Expanders

Each individually addressable Only 2 pins on microcontroller needed (SCL, SDA)

Expanders will handle photocells and switches MCP23017 by Microchip

Positional Motors

2 Stepper Motors 5 V, 7.5° step angle

2 Aluminum Timing Belt Pulleys

2 Urethane Timing Belts 40” length, ¼” wide

2 tracks perpendicular to platform for alignment

Electromagnet

motor_x

motor_y

Y-axis Track

pulley_ypulley_x

Positional Motors

Motor Stepping Pattern +5 V

Darlington Arrays

(ULN2064b)

8-Wire Stepper Motor

+5 V

Coil 1 Coil 2 Coil 3 Coil 4

Step 1 0 1 1 1

Step 2 1 0 1 1

Step 3 1 1 0 1

Step 4 1 1 1 0

Capturing a Piece

If a piece to be removed is horizontally blocked from the removal squares, 1. Blocking pieces are each moved down one square 2. The captured piece is moved to its appropriate removal square3. Blocking pieces that had to be moved are returned to their starting

positions. 4. The actual “jumping” movement take place.

→

1. Remove Captured Red Piece, 2. Move the Jumping White Piece

Software Algorithm

Minimax Algorithm Recursive algorithm which calculates best possible

score of future moves Difficulty setting determines number of moves to

calculate (Easy = 2, Medium = 3, Hard = 4) Scoring events

Capturing pieces (higher score for capturing ‘kinged’ pieces than normal checkers)

Attaining key positions on the board (positions along left/right edges of board for normal checkers, any edge position for ‘kinged’ piece)

Anticipated Problem Areas

Experimenting with electromagnet Wiring

Placing photocells in board and wiring so that magnet can pass as close to the surface as possible

Keeping wiring out of the way of the moving electromagnet

Power source must be investigated

Testing Strategies Motor Testing

Verify that it takes 54.5 steps to move 1 square 7.5 degrees / step = 48 steps / 360 degrees Circumference of pulley = 1.76 inches 1 step = 0.03665 inches

Photocell Testing Operation of game will be done in various lighting

environments to verify photocell functionality

Software Algorithm will be verified on personal computer so

that adjustments to scoring methods may be easily altered and re-simulated

System Integration Software algorithm completed and verified Software driver functions for I/O

Photocells LED’s Reset Switches

Motor verification Board creation Wiring to various I/O devices

Questions?

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