Functions and Constraints

The main function of the device will be to collect electrical signals from the abdominal skin surface for at least 24-hours and the have a sampling rate of at least 100Hz, to allow for collection of colonic data and heart rate data. It is also necessary for the device to save the data collected to a SD card, and for the device to have simple to use user interface. The goal is for the electrical components to be wireless and wearable. The constraints include battery life, durability, user comfort.  

Battery life

One part of the user-friendly design would be to have a long-enough lasting battery, the battery must last for at least 24 hours after one charge. A battery that could last for greater than 24 hours would be a benefit, as it would allow for even longer studies, but the absolute minimum is 24 hours of charge. We want the battery to last the time with only one charge so the device can be charged before it is given to the research participant and will not need to be charged again until the participant returns the device. We do not want to hand the responsibility of charging the device off to the participant. This means that less responsibility is placed on the participant which can make the testing process more robust. 

Durability

The average American male weight is approximately 199 lbs, so we would like our box to withstand at least 200 lbs in case a participant sits on our box (Elflein, 2022).  The housing unit box will be what protects the electrical components during the time the participant is wearing the electrodes. It is important that the participant can comfortably go about their day without worries that the box will break.  

User Comfort

Our aim is for the electrical box to be easily portable. Currently, this means reducing the size of the box as much as possible. We are using 9 x 5 x 2cm as a rough guideline for the box size, which comes from the dimensions of the current electrical components.  We also want it to be as light as possible to allow for the device to not disrupt the participant’s day-to-day life. The participant will need the device to be on their person, so having an electrical box with a user-friendly design with a method to attach it to their clothing or body throughout the day must be considered. 

As for connecting the electrodes to the electrical box, we must find connectors that are flexible, durable and maintain a secure connection with an easy interface. The current design’s connectors are very fragile and limit movement, so we aim to increase the durability of the connections and house most of the connections inside the protective box. 

Additionally, although we have a reasonable budget to work with for this capstone, we must be mindful when making decisions about ordering components for testing, mounting components to the printed circuit board (PCB) and building the housing unit. The manufacturability and serviceability, that is making sure the parts can be easily sourced and outside sources for building are easily accessible, are key in that it can be inexpensively and reliably produced.