Design Process

Design Decision

With the two designs proposed, there are a few major design tradeoffs:

Cost: The PWM IC is considerably less expensive than a microcontroller. Since this is a major factor in the project, the PWM IC is the better choice here.

Implementation: The PWM IC requires a simpler design and implementation than a microcontroller. A PWM IC was very specific inputs and outputs where with a microcontroller the inputs and outputs are mainly determined by software. The microcontroller also requires a software package to control the system. The benefit of a microcontroller over a PWM IC is the wide range of extra features that can be implemented into the design.

The design NAU Motor Systems has chosen is the PWM design. This was a matter of cost since a main goal of the project is to reduce price of the motor controller. The final decision came from Electric Blue Motors. This design reduces cost and complications with software bugs and updates and in the time frame of this project, finishing the PWM design for Electric Blue Motors is more realistic.

Another major design decision for the project is the use of four MOSFETs versus one MOSFET. With one MOSFET the entire load is controlled and dependant on one device. This is a major safety concern due to the risk of failure of the single MOSFET. If this MOSFET fails open, there are no other MOSFETs to prevent the entire load going straight to the motor. With four MOSFETs the risk of total failure is much less. If a single MOSFET fails, the other devices can prevent the motor from getting the full load of the batteries. The team chose the PWM design with four MOSFETs as the best option for their system. This was a major milestone as it allowed the team to start designing the circuit.