Hagrid is the prototype of a robot design that I've been working on for a few years now. This massive robot chassis uses parts from Powerwheels cars, so that it can navigate rough terrain. It's designed to carry a laptop and to be a platform for robotics experiments.
The four powerful motors in these powerwheels robots about 20 total amps. Commercial controllers capable of the high power required for this robot's motors are expensive. I decided to build my own to see if I could do it cheaper and gain a better understanding of the technology.
The high currents involved mean that if I make a design mistake, the controller goes up in smoke. I've rebuilt the motor controller many times.