CheckersBot

The project uses three servo motors and one webcam
The plan motion is insured by 2 servomotors and a third servomotor is used to activate the gripper as stated before. A webcam is used to recognize the pieces and their positions.

Servomotors:
1- For the plan motion the following motors were used (imposed).
2- This servo controls the gripper. It was chosen because it has small weight and due to the small weight of the gripper, in addition the torque needed to control the gripper's arms is very small, we can turn it manually without effort, hence the torque is not a design factor. And should rotate at least 180 degree.

A servomotor has been used in order to activate the gripper because a precise rotation angle is needed; the gripper needs an angle range that is well defined. In addition back-drivability is very important; in fact the motor should be able to turn in both directions so that the gripping and releasing actions could be achieved. Also the servomotors are reliable and simple to control.

Webcam: the webcam that is used has a resolution of 0.3 megapixels. The resolution isn't an important factor in our case, because the colours of the board are black, white, red and green. These colours can be treated separately using filters and the board could be easily recognized. In the software part, a more in-depth explanation will be presented

Microcontroller: To control all these elements an Arduino Uno board was used to make the tests, but for the final prototype a PCB was also designed and we used only the parts of the Arduino that we needed. In fact we only kept the features that were interesting in our case. Namely we kept the microprocessor, oscillating quartz of 16 MHz, voltage regulators to supply the motors, and a FT232 module equipped with a type B USB to ensure the constant communication between the Computer and the Microcontroller.

Eagle: To design the printed circuit boards the program EAGLE is used.

Once all these components were linked to each other, the second part of the design began which was the board design. This part consisted on displaying how the real PCB would look like, physical connections between the components.

The realization of the PCB was also done by soldering the components on the PCB board.

The configuration schematics were obtained in the data sheet of each component.
- The control system is the Arduino ATMEGA (dip) with a clock of 16 MHz. The following schematic shows also a reset button with a pull up configuration to prevent the input line from floating.

- Power supply: the power supply is provided by linear voltage regulator to get the right level voltage in order to have a good performance of the servomotors. Regulators of 5 and 6 volts were used with 1 A to 2.2 A of output currents.

- Serial communication: USB powered situation using a 232 FT communicator. This configuration supplies the power to the controller from the USB (computer).

PCB schematic and board layout.

Realization of the PCB.

The PCB obtained was performant. The voltage regulators worked as expected. But the seiral communication showed some problems. When connecting the PCB to the computer, a voltage of 5V was observed but the arduino programm always said that the microcontroller was not in sync. Other groups had the same problems with the arduino PCB when connecting and deconnecting the microprocessor. The source of the problem is still a mystery.

To ensure a good functionning of the robot, we decided to control the motors with the Arduino PCB and the power supply will be provided by the PCB