P18463: Water Powered USB Charger
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

As MSD I draws to a close, so does the amount of time to make crucial design decisions before the build begins. In order to mitigate risks and problems during MSD II, the team needed to review and update the feasibility of each subsystem and focus on how the subsystems would be integrated during the build. The first and most simple sanity check is making sure all of the components can spatially fit in the geometries we are envisioning. The finalized CAD file will reflect the dimensions of each of the components needed for subsystem functionality.

A crucial component in ensuring the accuracy of our CAD model is comparing it to our current Bill of Materials in order to verify the design includes all of the intended components. Each entry in the Bill of Materials needs to identify which subsystem the entry will be used for, and whether or not these are purely material expenses or costs associated with developing the product.

What we managed to get done this phase was update our turbine blade design and simulation, update the method of waterproofing the housing, clean up the wiring diagram, determine what accessories are needed, generate a Bill of Materials for the prototype, and update our Risks.

Turbine Design

Progress & Planning

One of the bigger focuses for the ME's for this phase of the project was determining the turbine and any associated risks that would come along such a turbine. To determine the most effective turbine, fluid simulations were run through SOLIDWORKS flow simulation software. The output we were looking for was the highest power output. However this power output had to come with reasonable turbine characteristics.

The chosen turbine length had to give enough room to internal components and fixtures that would be placed in the housing. The turbine also had to satisfy the cross sectional area constraints that we had determined through MatLab in the previous sections of the project. The turbine also needed to be light and economical to 3D print, and needed to decrease any instability that might have occurred during use. Ultimately, the turbine had to create the most power possible, which this current design seems to do.

One of the most challenging aspects of this turbine was the connection method to the USB Charger itself. This connector is still potentially going to change if we run into 3D printing problems. But our current design employs the sidewalls of the turbine itself to increase the surface area through which the tabs connect to. These tabs that reach the drive center pieces of the turbine assembly (the bearing on the lower end and the drive shaft on the upper end).

Analysis & Simulation

Data from parametric study run on turbines through SOLIDWORKS Flow Simulation

Data from parametric study run on turbines through SOLIDWORKS Flow Simulation

The data above helped prove why the best choice was a flat angled turbine. This was not the expected result however from the data we can see throughout the ranges of velocities that the tests were run on, the most power was produced with the angle of the blade effectively 0. This saved us time and money that we would have spent on the turbine testing part of this project, because now instead of running 20-30 different turbines, we can identify which one we want to run and compare that single turbine to the expected results and then the maximum theoretical output to attain its efficiency.

The above file can be accessed through excel by clicking on the following link: CFD Analysis Data

Drawings and Schematics

Turbine

Turbine

Connection point to join housing to turbine blades

Connection point to join housing to turbine blades

Test Plans

Turbine Test Plans

Turbine Test Plans

The Test Plan Document can be found here: Test Plans

Housing and Waterproofing

Progress & Planning

We have identified that the most economical and sane way to seal the rotating drive shaft would be through lip seals. Multiple options were available, and the most secure method used to seal rotating components in the industry are mechanical seals. However, for our application, where the pressure drop will be almost insignificant, lip seals make the most sense. We also checked other companies (such as E-Steam) and found out that they too use lip seals to waterproof the shaft seal.

We will also be using gels and coatings - primarily silicon-based - to insulate the internal components from impacts and moisture. The interior of the components have proved to be smaller than we have initially planned for; this is great for design flexibility. If certain tests warrant that we change out design, there is now available room on the device that we can either use or get rid of.

In order to insulate the internal generator and voltage regulator, we will size the ovular casing just larger than the generator. After connecting the voltage regulator to the generator, we will coat the sides of the housing with the warm silicon adhesive and slide the generator anchoring piece to the back of the housing where it can set. The driveshaft will extend out of the back of the housing.

The team has selected the GE Iron Grip Silicon Adhesive to use in this application due to its extremely versatile range of surfaces it can be applied to, as well as its extremely effective resistance to impacts and water. It is also GREENGUARD certified, meaning it meets stellar standards for low indoor harmful emissions.

The team is also researching the use of coatings for the bottoms of boats on the exterior of the housing and fins of the device. While they appear to add durability and reduce friction with the water, we are still unsure how these coatings would behave when applied to ABS. Contacting manufacturers will be a major part of next semester when purchasing begins to pick up.

Drawings and Schematics

Cross Sectional View of Components of Charger

Cross Sectional View of Components of Charger

Exploded View Labeled - Part 1

Exploded View Labeled - Part 1

Exploded View Labeled - Part 2

Exploded View Labeled - Part 2

Exploded View Labeled - Part 3

Exploded View Labeled - Part 3

Test Plans & Data Sheets

Waterproofing Test Plans

Waterproofing Test Plans

The Test Plan Document can be found here: Test Plans

Generator & Voltage Regulator Selection

Progress & Planning

Generator and voltage regulator purchase options are finalized and ready to be ordered. The electrical wiring diagram is ready and is shown below in the Drawings & Schematics section. The voltage regulator comes as a package consisting of the necessary required components for successful voltage regulation. Generator and voltage regulator overheating will be countered by the water flowing over the casing which should keep the internal electrical components operating within an optimal temperature range with varying water flow as well as taking into account direct heat from the sun.

Analysis & Simulation

Power will be transmitted through a rigid cable from the device in water to the power bank on shore and there will losses. Based on our selected cable and standard phone battery specs, these losses are theoretically very minimal. Trickle charging is preferred and hence the selected voltage regulator is capable of transmitting a low current to the connected power bank and phone.

Drawings and Schematics

Shown below is the electrical interconnection wiring diagram which shows all the required electrical connections.
Electrical Components Wiring Diagram

Electrical Components Wiring Diagram

Test Plans & Data Sheets

Attached are the links to the test plan and product datasheets below. First is the Generator Test Plans:
Generator Test Plans

Generator Test Plans

Next is the Voltage Regulator Test Plans:

Voltage Regulator Test Plans

Voltage Regulator Test Plans

The Test Plan Document can be found here: Test Plans

The DC Motor Specification Sheet can be found here: DC Motor Specifications

The Voltage Regulator Specification Sheet can be found here: Voltage Regulator Specifications

Accessories

Progress & Planning

Electrical accessories selected for this design consist of Mini USB and USB cable connectors, power cable itself and a power bank. The device will run through a number of tests in order to determine successful functionality.

Analysis & Simulation

The rigidity of the connections would require testing in order to be sure if these components would not disconnect when in operation. The soldering of the connections need to be good enough for them to withstand the durability tests. This is covered in our engineering requirements as ERS13.

Data Sheets

Attached are the links to the product datasheets below

The Cable Specifications can be found here: Cable Specifications

The Powerbank Specifications can be found here: Powerbank Specifications

Packaging

Progress & Planning

The original plan had been to model our case as something relatively similar to a cylinder and have it 3D printed out of ABS. Unfortunately, we recently discovered limiting size constraints in the Construct here at RIT. Research for existing forms of packaging are in place, but the packaging is a lower risk item that is not on the critical path. The main risk is leaving enough lead time in the event that we need to order a more expensive, customized case.

Test Plans

Packaging Test Plans

Packaging Test Plans

The Test Plan Document can be found here: Test Plans

Bill of Material (BOM)

BOM For Device only

BOM For Device only

The above document can also be found in the following link: BOM for device only

Design and Flowcharts

The system and subsystem architectures have not changed in functionality. Small additional components have been added to the BOM, but are too insignificant to add to the subsystem flow chart. The overall nature of this system is linear in terms of subsystem interaction; the input for one is the output of another. The flow charts can be found below:

System Architecture

System Architecture

Subsystem Inputs & Outputs

Subsystem Inputs & Outputs

Risk Assessment

The focus of Phase 4 was moving as many risks as possible into the "Resolved" section of our Risk Analysis. Additionally, two key risks have been recognized in Phase 4 and are currently being addressed.

Below is a screenshot of all working risks. These risks each specific have plans to address them, but are typically more complicated, require more attention, and have a higher chance of presenting problems during the build.

Working Risks

Working Risks

All other risks have more or less been resolved.

The Risk Assessment Document can be found here: Risk Assessment

Design Review Materials

The Project Summary Sheet gives a quick snapshot of the key risks, progressions, action items, and a list of questions for the guides. It can be found at the link below:

Project Summary Sheet

The Presentation Outline document gives an overview of the Detailed Design Review Agenda. The review will cover major resolutions in this phase, tasks that are still in progress, and a summary of how we intend move forward with testing, building, and integrating out subsystems in MSD II. It can be found at the link below:

Detailed Design Review Presentation Outline

The Presentation slides are what will be shown during the Detailed Design Review. These slides encompass all of the major progressions, potential setbacks, and things we have all learned throughout MSD I and how we intend to prepare for MSD II. The link to the slides can be found below:

Detailed Design Review Presentation

Plans for next phase

The size restrictions for the 3D printers at the RIT Construct are proving to be most inconvenient for the team. In order to stick to the critical path, the issue must be promptly resolved. We will be working to design the parts in such a manner that they can be printed and assembled modularly. Ordering a print from a third party would be far too costly, time consuming, and leave little to no room for error.

The team will be tackling this issue and advancing the other subsystems in parallel. Due to the new turbine testing procedure, the electrical and waterproofing subsystems will have to be tested and completed first. This allows the team to stay on track with the critical path and allow time to potentially redesign the turbine blades. Once the issues along the critical path have progressed, the team will begin to focus on lower-risk items like the packaging for the device.

Ideally, the schedule will leave the team with two or three weeks of redesign time in the event that case major design pivots or improvements are necessary.


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