Pill Centering Module
The problem of centering the pill and aligning it under a blade is non-trivial. Many designs were considered such as modifying a bar scanner to utilized an array of LEDs to detect where the pill is. Eventually mechanical means were chosen in favor of reliability and repeatability.
Our team realized that two pins, equidistance from a center point could easily align a pill. The question was by what means would we be able keep the two pins equidistance without a complicated feedback controller. It was suggested that we use two bolts welded back to back to manipulate the positioning of the alignment rods.
If the threads of two bolts, with opposing thread direction, were welded back to back one could manipulate the positioning of two alignment rods with respect to a center position by turning a single rod. This will keep the alignment rods equidistance, and it eliminates the need for multiple sources of movement. Because left handed screws are quite rare, we instead chose to disassemble an turnbuckle. The process was similar to this.
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| The turnbuckle is first cut in half, trimmed to size then flattened to make it more square. This was necessary to recover a left hand screw of appropriate size. |
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| Here the final result can be seen. A standard right hand nut for right side. Two stainless steel screws were then brazed together to form the inner gear. |
The inner gear comprised of two stainless steel screws that were brazed together. Excess solder was lathed off. An aluminum block was then profiled to create a pathway for the turnbuckle. The motor was then crimped to the aluminum block. The inner gear would be rotated by a geared motor being activated by a bi-polar stepper motor controller. The motor controller sends pulses of defined width using a crystal oscillating clock and a 555 timer. A potentiometer than varies the speed of the rotating inner gear, and thus the speed of the two alignment rods going to or from center.
A video of the centering module being tested for functionality can be found here| Concept Centering Module w/ integrated cutter | |
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