Collaborators: Eli Abidor 

Project Dates: 1/5/2013-6/10/2013

Prior to designing the PID Cruise Control throttle for the Northeastern Solar Boat Team we designed a manual throttle to race the team's electric boat at the National Solar Splash Competition. 

We picked three standard 3200 RPM Etek DC electric motors for the drive train based on our budget constraints, their relatively high power output and their mechanical compatibility with the existing drive train. The competition limits battery capacity by total weight instead of voltage which limited our motor drive voltage when designing the system.  Due to the battery weight constraints we ended up driving the motors at 36 V instead of the maximum drive potential of 48 V.

We chose to drive the motors with 36 V Alltrax Axe motor controllers. The controllers were chosen due to their low latency, rugged design and extensive documentation. There were more affordable controllers that worked  with a greater voltage range which would allow for easier changes to our design in future iterations, however due to the lack of documentation we decided it wasn't worth delaying our build schedule to work with products with a greater learning curve.

The motor controllers had existing configurations for a 0-5k throttle and for a signal from a 0-5V signal. Although the manual system only requires a 0-5k throttle we already had future plans to make a cruise control system that would more smartly discharge the boat batteries throughout an endurance race and so configured the system for a 0-5V signal so it would be easier to integrate the cruise control system. 

The voltage seen by the motor controllers was determined by a calculated voltage drop across a potentiometer in a basic voltage divider circuit.  Posi lock and Wago connectors were used for the connections between the throttle, the motor controllers and peripheral components due to their durability and potential to allow for testing and integrating new components into the system.