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Old 11-21-2010, 07:22 AM   #4 (permalink)
Greg Fordyce
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Join Date: Nov 2009
Location: Scottish Borders, Scotland
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Originally Posted by mrbigh View Post
Greg, what is the outcome of your Arduino interface?
Sadly at the moment it is on hold. The first priority is getting my EV on the road, after all the CougArd Explorer isn't much use without an EV to put it in. I have all the bits, but other things keep getting in the way, work, major house renovations and life in general. I am thinking about buying a can of time, but even it's on back order!

Seriously though, I am moving away from the Arduino platform for this, at least for the moment. The original reason for choosing the Arduino was because my BMS couldn't support serial comms faster than 9600 baud and the Cougar is at 19200. So the idea was for the CougArd Explorer to sit in between the Controller and my BMS and maybe eventually move the BMS master functions to the CougArd Explorer.

But things have changed on the BMS front and the project can now support 19200 baud serial comms. This is because we have moved from the original Picaxe chips to using bare Microchip pics and the Pic Basic Pro development environment. So now I have the possibility of directly connecting the bms to the controller. The first task will be to get the current limit working as I described above when the battery pack starts getting low. Then I want to monitor data from the controller starting with battery amps and amp hour data. The BMS has a built in current measurement, but I want to use the bms current data for battery charging and dc-dc loads from my pack. This will allow a smaller and more accurate sensor for this and use the controllers motor amp sensor for the motor load.

With the Arduino I was able to send commands to the controller and also read the serial data. Parsing the data string and storing the values to variables was proving a bit harder, but this looks to be quite simple with PicBasic, although I haven't actually tried it yet. Another advantage of PicBasic over the Arduino is connection is possible with a couple of resistors, no RS232 level shifter required.

My plan is to get the car on the road soon and get back to working on this project early in the new year.

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