Magnetic Levitation
Build and/or program a Proportional Integral Differential (PID) controller to maintain the height of a steel ball bearing below an electromagnetic coil. This one is considerably more difficult than levitating a ping-pong ball in a tube, but it's also way cooler.The apparatus was built by Eric Ayars, starting with a design used in the Advanced Lab at UC Berkeley. It has been done successfully twice so far: once using an op-amp circuit (Dr. Ayars) and once using a Teensy 3.1 microcontroller (Charris Gabaldon and Robert Keen, 2016.) Note that it does not work with an Arduino (the Arduino PWM frequency is too low.) Whether it's possible with a LabVIEW program is still an open question.
Regardless of the control mechanism used, you'll have to build your own photodiode amplifier circuit. Refer to your PHYS 327 notes, or to Dr. Ayars.
Reading
- More than you ever want to know about this topic, by John Bechhoefer
- Figure 2 from this handout may be helpful for building your light sensor
Location
Room 108, cabinet 108.24.
Additional equipment needed
- 12V 2A power supply, possibly bipolar depending on if you're using op-amps or not.
- ELVIS II board, if using LabVIEW for control.
- Teensy 3.1 or 3.2 microcontroller, if using microcontroller PID control.
- Op-amps (TL06x is a good choice, as is LF411) if you're going that route.
- Power MOSFET(s) to drive the coil.
Cautions
- None. This is a completely non-hazardous lab.