MAT - Magic Angle Turning 2000 - 2001 Developed by Kunal Kandekar and Subodh Joshi * INTRODUCTION This was undertaken a final-year project for our Bachelor of Engineering (BE) degree in Instrumentation & Control engineering. We implemented a real-time embedded control system for "Magic Angle Turning" for specialized Nuclear Magnetic Resonance (NMR) experiments. All (except a vanishingly small minority, e.g. us) of NMR experiments utilize something called "Magic Angle Spinning" (MAS). Here, the sample to be analyzed is oriented at the magic angle (54.7356 degrees) and spun at very high speeds (multiples at KHz) in a ridiculously strong magnetic field. (And I mean RIDICULOUSLY; google for "MRI accidents" -- MRI is comparable to NMR) Our project applied to a very specialized form of experimentation, called Magic Angle Turning (MAT) where the sample is turned at much lower speeds (30 to 100 Hz). Since conventional NMR equipment was not designed for MAT, specialized eqiupment (such as ours) is required. We wrote the code in raw 8051 assembly, using an Atmel 8051 microcontroller. * NEAT HACKS We used the voice coil of a cheap audio speaker (literally ripped out of a PC speaker) to precisely modulate pneumatic pressure. Check out "flapper-nozzle" for it's doable. Also, check out the "32 bit by 16 bit division" routine. It divides a 32-bit number by a 16-bit number on an 8-bit device in raw 8051 assembly. No floating point, of course. It takes advantage of a specialized 16-bit by 8-bit division instruction our Atmel microcontroller had. With his, we were able to measure frequency from inter-interrupt intervals (heheheh, just made that up) up to 2 decimal places of accuracy. This level of accuracy was needed to maintain a stable spinning speed, since only a 0.01 variance is tolerable for MAT NMR experiments.
kunalkandekar/MAT-NMR
Source for a 8051 microcontroller-based real-time embedded control system for Magic Angle Turning NMR experiments.
AssemblyNOASSERTION