In this phase, we focused on designing the dispensing cup support (in yellow), the dispensing cup, and the inner disc.
The holes in the dispensing cup and the inner disc should align in order for the pills to be successfully dispensed. The shapes and sizes of the holes are designed to correspond to the shapes and sizes of the 3 types of pills that we have selected.
Communication with the software members was key at this stage to ensure that the rotation of the disc (via the stepper motor and the motor shaft) is 360 degrees anticlockwise for the dispensing of each pill. As the stepper motor has a relatively low rpm (value?), the cup stays in place while the disc rotates 360 degrees anticlockwise, and the disc stops against the lock for every complete rotation.
However, to ensure that a pill is dispensed with every complete rotation, a new function was added in the Arduino code to “jiggle” the dispensing cup. This “jiggle” motion was a fast motion at 22200 rpm, to 40 degrees in alternating clockwise and anticlockwise directions. The fast alternating rotations cause the dispensing cup to move, thus the dispensing cup and the inner disc are no longer aligned at their respective fixed angles, affecting the dispensing mechanism. The inner disc may grind against the inner wall of the dispensing cup, increasing the distance between the inner disc and the dispensing cup, so pills may drop between rotations instead of one pill being dispensed for each complete revolution of the inner disc. Therefore, an additional stopper (in purple) was fixed onto the dispensing cup support (in yellow) to lock the dispensing cup in place throughout the “jiggle” motion. The holes in the dispensing cup and the inner disc should align in order for the pills to be successfully dispensed.
The shapes and sizes of the holes are designed to correspond to the shapes and sizes of the 3 types of pills that we have selected. The knob on each disc allows for easy removal of the disc should the pill dispenser jam while dispensing pills.
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We finalized the 3 types of pills that we will test with our pill dispenser (see list below)! All pills are purchased from Holland and Barrett.
- Size 00 capsules
https://www.hollandandbarrett.com/shop/product/holland-barrett-turmeric-500mg-capsules-60000525
- Round flat pill
https://hollandandbarrett.com.sg/products/good-n-natural-bilberry-100-tablets-375mg
- Oval flat pill
These 3 pill shapes are standardized shapes most commonly found among medications and supplements that are manufactured today. For capsules, which are defined as _____, size 00 capsules are the most frequently found in pharmaceutical products. However, for oval and round pills, there is great variety in pill sizes and pill weights according to the contents of the pill, thus we wanted to conduct a variety of trials with our pill dispenser using pills with different weights and different sizes (length, width, height). We hope to design a pill dispenser that is versatile and customizable, to accommodate the lifestyles of different users.
We also tried to use an oblong flat pill, but decided not to proceed with it because it was too heavy and there was greater friction between the pill surface and the slide; the oblong flat pill barely slides down the slide at an inclination angle of 20 degrees.