Low Side Chopper!

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Breaks at MIT are always wonderfully magical times. If you’re motivated enough, you have all the resources you could ever want combined with free time. What better combination is there?

Seeing as MITERS was currently transitioning out of the Battlebot phase, and everyone was working on electric vehicles again, I decided I would take a slight exploration and make one for myself.

Inspired by some 24v wheelchair motors my roommate and I had found at the Loading Dock a few months earlier, and the abundant 12s4p A123 packs MITERS had I decided to make a derpy vehicle to get used to things I haven’t dealt with like steering, higher voltages, etc.

First step, SPEED CONTROLLER!

Thus the low side chopper was born.

A while back, MITERS folk had bought a large quantity of Brems-Choppers, these fantastic 1700 V, 1000(ish)A continuous IGBTs for Tesla coil shenanigans. They’re also pretty great (albeit a “little” overkill) for derpy brushed motor controllers.

The low side chopper is a single directional speed controller only using the low side FET (hence low side). Mine uses some random gate drive we had lying around, along with an arduino pro mini for logic. I used a linear pot for throttle input. Everything was just potted in hot glue later for “waterproofing”

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Somehow, it worked magically (without any magic smoke) after a couple hours of work.

Derp vehicle was in business!

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