Ramp input testing of the custom speed controller we are developing for the cap kart. (http://web.mit.edu/first/kart)

Speed control is done by rapidly switching voltage on to and off of the motor coils. In this video, you can hear the speed controller switching frequency as it ramps up and down (high-pitched whine). It is most noticeable at about half speed.

Our speed controller is entirely custom, built in-house. Testing here is with very little load, just the inertia of the rear axle. However, since no heating of the power transistors used to switch was seen, we will be stepping up to load testing very soon.

We hope to be able to handle a maximum current of 300A. The total component cost to build our speed controller will be less than $100 and plans will be made available on our web site if (when) it has fully proven itself.