Monday, May 16, 2011

< Summer Projects >

While studying for finals I realized something, and that is procrastination, NOT necessity, is the mother of invention. With the dark cloud of exams looming overhead my mind naturally started generating ideas for the more exciting ways I could be spending my time. Now that they are over* my ideas are rapidly coming into fruition.

Motors Controllers:

After working with servo's for far too long, I bought some TI SN754410 quad half H-bridges and Sparkfun's cheapest motor, which turned out to also be their smallest! I wrote a quick Arduino/Processing sketch and touchOSC layout to integrate my iPhone control process to this tiny motor. It's very straight-forward, just PWMing the enable pin to control the speed. This was a success.

More recently, a friend handed me a hard drive spindle motor after realizing that a battery and wires alone could not bring it to life. It even has four wires, "what could the extra two do?" he might have asked. I knew it must be brushless and after a little bit of research, it turns out it's a 3-phase BLDC. There is one wire for each phase and the fourth is common. In a trial by fire effort I am in the process of building a controller with some parts I had lying around.

The basic idea is to drive each of the phases with one side with one, or one half-bridge. Thus two SN754410s are used. The Arduino Nano provides the PWMing for the three enable pins, the inputs for the six logic pins, and the back-EMF sensing. The latter will be the tricky part, and I am still doing some reading to determine the best way to do that -both in hardware and software. This is a sensorless motor, meaning instead of onboard hall-effect sensors the position of the rotor is approximated by detecting the back-EMF. Not any easy undertaking, and for now just a clusterfuck of wires.

In the background -or maybe the foreground- another project is in the making. Today I ordered a 3-axis accelerometer and a 20x4 LCD. I've had an itch to start working with inertial sensors for some time and I think I've found the perfect application. Hmm what could those be for? Hint: my car.

*one non-engineering final left

No comments:

Post a Comment