Monday, November 18, 2013

Custom Electronics from the EE Team


The EE team this year is working on some custom electronics in addition to all of the COTS (commercial off the shelf) work we do on the larger electric vehicles. Our responsibility has grown to not only include the interface and safety circuitry for the large motor controller, battery pack, and system logger for the trike but also a variety of custom electronics.
We have two (new) main projects):

  1. Electronic actuation of a brake system for the NY bike trailer
  2. A custom BMS (battery management system) for small (bike) to medium (moped/go-cart) electric vehicles
In addition to these two tasks, its also my job to teach electronics to the EE-team; the engineering goals of the projects have to balance cost, effectiveness, and the potential to teach electronics design principles.

Our lab space was recently upgraded with a new electronics test bench (courtesy of the MIT Edgerton Center) to accommodate, in part, our new role.

Brake system

We needed a way of actuating a pair of rim brakes on the bike trailer, and while a mechanical linkage was preferred initially, mocking up the requirements for quick disconnects and cable pull routing lead us to shift to electrical actuation. The system uses a worm-driven motor to pull and release the brake cable; because this can not be back driven (a property of the work gear) the motor does not need to stall to continue apply brake force. While the ME's worked on enclosures and mounting, team produced a schematic and a board layout for this task using an Attiny85 micro-controller at the center. 
Layout for NY-bike-trailer-brakes

Battery Management System

We are working on a battery management system that is fully modular. Someone who wants to build an EV, once our system is complete, could connect several 4s2p modules together with a central controller to form a 'smart pack' capable of self balancing and charging. We are still at the system design level and currently working on a digital communications bus to communicate between all of the individual modules.

More updates are coming your way in the future.
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