As some of you are aware, I am a member of the University of Manitoba SAE (Society of Automotive Engineers) Formula Hybrid team. The major project that I have been working on for a while now is a CAN bus controller Arduino shield. The system is based on the one designed by Mike Sefton last year. We are using the same CAN interpreter because the manufacturer was generous enough to donate some chips to us. These chips work well, but they are designed to be used with an OBDII reader, so we are using a few work arounds to get the system to work for us the way we need.
Aside from some simple changes to the circuit, there are two major changes to the system. First, I added a the NUP2105L chip to the CAN bus to give us some over-voltage protection. The major cause of failure last year was over-voltage, which is always a concern when dealing with electric vehicles. The second change was to allow an outside system to communicate with the CAN controller over a serial connection. Last year the CAN devices were controlled directly by the Arduino, but this year the Arduino is basically a middle man that can do some processing of commands if needed.
For the hardware design, I decided to try out a few open source tools. I first tried KiCad because it was more cross platform and a fully integrated suite. There were some things I didn’t like about it though (although I may have just been looking in the wrong place for the feature I thought was missing) so I decided to try out gEDA. I personally liked the feel of gschem better than KiCad’s schematic editor, and the PCB software seemed quite good to me too. The workflow between tools is a bit less intuitive, requiring a few terminal commands, but I am quite comfortable with the command line, so I can see myself using gEDA much more in the future.
The files for the hardware design are posted here: HARDWARE
The firmware for the Arduino is posted here: FIRMWARE
The firmware is currently a very basic repeater but will likely see changes once we start figuring out what specific features we will need. Feel free to post a comment or send me an email if you have any questions about the design.
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