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Student Projects |
Hardware: The body of the robot is built from a Japanese remote controled rock crawler. We took the treads, motor, and a few pieces of the frame to build the body. The motors were driven with a FAN8200 low voltage h-bridge. The microcontroller used was the Parallax BASIC Stamp SX. For wall sensors we used a very simple light sensor. It consisted of an ultra bright white LED paired with a photoresistor. This was sent through a voltage comparator and into the microcontroller.
Software: Because we were limited in memory, a modified flooding algorithm was used. The robot would make its decision based on which way would get it closer to the center of the maze.
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George Keiser and Nicholas Truncale undertook a project to re-build a scanning tunneling microscope that was first purchased in 1988 which needed major repairs. The most basic function of a STM is to lower a metalic tip extremely close(4-9 Angstroms) to a sample of interest. A quantum tunneling phenomena occurs, creating a current flow from the tip to the sample or vice versa. This current is proportional to the distance between the tip and the sample. The result of this is a topographical readout of the sample surface. Hardware: This particular apparatus had a damaged piezo-actuator along with its head, which was the mechanism that lowered the tip very close to the sample with angstrom level precision. The electronics were also out of date and had to be created from scratch. We purchased piezo-actuators and built a custom head from common lab supplies. The piezos were powered by an opto-coupler circuit that we designed to isolate the high voltage portion of the circuitry from the amplifier portion due to noise. This opto-coupler circuit is powered by common wall voltage and is controlled by a USB data acquisition device. This device outputs 0-5 volts into the opto-coupler circuit which is then converted to 100-140 volts and sent to the piezos. The amplifier, which sits in the head apparatus, is a common JFET that will amplify our tunneling current(5-30 nA) and convert it to a readable voltage by our data acquisition device. Low pass filters were also implemented to nullify 60 Hz and 120 Hz noise from out DC tunneling current. All of this is located in the head portion of the apparatus. Infromation is sent via ribbon cable to more circuitry including the digital logic for our stepper motor control. The USB DAQ dends out signals to control our stepper motor. The original hardware was kept because of its pristine condition. Software: One of the goals of this project was to step away from total hardware control and attempt to implement some software control. Using Labview, the scanning portion of the STM is totally software based. The basic process included moving the stepper for coarse control and then oscillating the piezo until a tunneling current is initialized. A method called constant current mode is used to then laterally scan the sample and create a contour plot of the sample giving us the topography. |