Updated motor controller

The re-designed motor controller

The motor controller has had the largest update of all the boards, however the general function of the board remains the same.

On the schematic the voltage regulator was removed as it is not required for the current generation of boards as they all run on a standard 5v TTL signal that is currently provided by the battery pack, the voltage regulator and the complimentary components also took up a large amount of room, which could have been used for other components or to provide more space the current parts.

A secondary trim-pot has been added, this allows for control over the speed of both wheels, so that it can be calibrated to go in a straight line, or if you reduce the speed of both wheels evenly, you could make the robot go slowly. Minor changes to the bottom and top silkscreens were made to help make the pin-outs and board labelling easier to understand, especially when viewing the board from the top.

The perimeter shape of the board has been altered to make better use of the paid-for area (You pay for a bounding box at OSH Park, so any cut-outs would be costly) This was also required for the second trim-pot as there would not have been enough room previously. I was also able to re-arrange various components to allow for more space between parts. Due to the extensive amount of redoing the tracks on the board, no vias were required, and there is a large amount of room between the majority of the tracks. 

The increase in spare space on the board enabled me to move the PCB switch location to a more suitable position, so that it would not be obscured by the shields that would be stacked on top. A secondary switch pin-out was put onto the board, in parallel to the first, this would allow you to add an external switch on the chassis (for example) and could provide the user with more elegant switch in order to turn the robot on.

A single 2-pin header was added to the board, which, when a shunt (shorter) is put on, it would short the VCC and the forward control pins of both motors, this would cause the robot to move forwards to allow the user to calibrate the trim-pots to make the robot move forwards in a straight line.

One aspect of the motor controller PCB that is yet to be updated is the layout of the mounting holes, so that it would be impossible for the motor controller, and therefore the shields with inputs/outputs, to be incorrectly orientated on the chassis.

The motor controller Eagle files discussed in this post (v0.5) can be downloaded from Dropbox.