P18347: Baby Stroller with HVAC
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

Phase 2 Team Vision Phase 2 Accomplishments Phase 3 Team Vision
Electrical Tasks
  • All components/kits will be inspected, assembled, and evaluated to ensure they are working (not broken or damaged in shipping)
  • Electrical components that were purchased as kits will be soldered together into complete packages
    • Relays
    • LCD display shield
  • Each subsystem will be assembled such that it will be ready to be programmed in Phase 3
  • Skeleton code of the main loop for the overall system will be outlined
  • Components/kits are inspected, assembled, and evaluated
  • Completed the skeleton code of the main loop for the overall system
  • Electrical components are soldered together
  • Electrical subsystem with breadboard prototype is completed
  • Debug and develop code of the main loop
    • Fix noise in temperature sensor
    • Program UI
    • Program input buttons
  • Convert breadboard components to PCB
  • Develop a battery charging method to be user friendly
Mechanical Tasks
  • Prototype the nichrome wire within insulation and perform the Heated Seat Functionality test
  • Using Stroller Pod Air Quality test to prove design of preliminary ventilation system (infiltration focused design). If test fails, begin design of forced air convection system for ventilation
  • Preliminary mounting locations for components that allow the stroller to fold up (wires, batteries, LDPE cover)
  • Final decisions on component placing have been completed
  • Developed preliminary heating system with insulation
  • Completed design of preliminary ventilation system (infiltration focused design)
  • Started CAD modeling of microcontroller box
  • Complete the heater system
  • Mount all components to stroller (battery, seat, wiring, microcontroller)
  • Complete microcontroller CAD modeling and determine how it will be manufactured
  • Connect the plastic covering and zipper to the stroller
Test Plans
  • Heated seat functionality
  • Battery capacity
  • Required foam thickness
  • Stroller pod air quality
  • Ventilation test
  • Heated seat functionality
  • Continue to test heated seat functionality
  • Controller testing (user interface)
  • Usability- ease of movement
  • Overall electrical charge on stroller

Test Results Summary

A preliminary version of the air quality test was completed this phase. It was run using both a humidifier and a water bottle filled with hot water, surrounded by low density polyethylene plastic. The procedure and results of both these tests are outlined in their own individual report linked below.

Additionally, a test tracker sheet was created to keep better track of when tests have been completed with a brief overview of their results.

Component Placement

Team sat down together to discuss various possibilities for mounting components that would result in the system taking away the least amount of space from the user and allowing the stroller to maintain its full range of collapsibility.

Battery

The battery will be mounted to the stroller within a 3D printed enclosure.

Preliminary Battery Box Design - Iso View

Preliminary Battery Box Design - Iso View

Preliminary Battery Box Design - Inside View

Preliminary Battery Box Design - Inside View

The team brainstormed a few solutions for mounting the battery to avoid offsetting weight and maintaining collapsibility of the stroller.

Option 1:

The battery box would be secured on parallel mounting bars welded or fasted on to the stroller frame. Slots would be cut into the parallels that screws would go through the top of the battery box to secure the box beneath the structure.

The main problem with this design option is that front wheel interferes with the space between the bars when collapsed. Additionally the orientation of the bars with the stroller offsets when collapsed, so any mounting bars for the battery would have to allow for automatic adjustability.

Battery Mounting Option 1 - Bars Beneath Seat

Battery Mounting Option 1 - Bars Beneath Seat

Option 2:

The battery box would be secured the bars that run beneath the basket. Fasteners would protrude through the basket material. Mounting screws would go through the bottom of the battery box to secure the box to the structure.

The main problems with this design option is that the battery box is taking away customer storage space and any electrical connections would need to be lengthened. This would increase the overall product cost and increase the risk of wires getting caught or cut.

Battery Mounting Option 2 - Corner in Basket

Battery Mounting Option 2 - Corner in Basket

Option 3:

The battery box would be secured the bars that run beneath the basket. Mounting screws would go through the top of the battery box to secure the box beneath the structure.

The main problem with this design is that the battery box is closest to the ground. The battery box would have the greatest exposure to harsh street environmental factors that could damage the structure and components: snow, salt, rain, dirt, rocks, etc.

Battery Mounting Option 3 - Bar Beneath Basket

Battery Mounting Option 3 - Bar Beneath Basket

Option 4:

The battery box would be suspended within a fabric sling that had a buckle and adjustable straps to tension the battery box in place behind the child's back.

The main problem with this design is the uncertainty in the product life-cycle of the fabrics that make up the sling. This method leaves more room for user misuse to occur. Additionally, if not secured properly, damage to the battery and system could be severe.

Battery Mounting Option 4 - Adjustable Tensioned Strap

Battery Mounting Option 4 - Adjustable Tensioned Strap

Temperature Sensor

Temperature sensor was placed to be within carriage space to measure enclosure temperature. Casing options need to be determined to protect sensor from child and potential spills.

Temperature Sensor Mounting - Beneath Tray

Temperature Sensor Mounting - Beneath Tray

Microcontroller

Microcontroller solutions were determined by the need of the display to be close to the caretaker to receive feedback from the system. Using the space formerly dedicate to the speakers and personal storage, the team will need to determine alternative personal device storage options or result in the customer losing this space to the technology.

Microcontroller Mounting - Within Storage Tray

Microcontroller Mounting - Within Storage Tray

Microcontroller Mounting - Space Removed for Mounting

Microcontroller Mounting - Space Removed for Mounting

Electrical Subsystems

The following is an overview of what what accomplished this phase; For a more detailed document check the P18347 Electrical Subsystem Status Update document.

Arduino code and screenshots can be found in the following compressed folder. P18347 Subsystem Review Mirco-controller Demos & Code

Temperature Sensing System

Initial decision to use the AD22100KT sensor that Ian already had has been reversed due to initial oversight in sensor's requirements for accurate data. Analog devices TMP36 sensor intended to be used instead.

Seat Heating System

Preliminary testing done with NiChrome wire and polyurethane foam. 24AWG wire was used spaced 3 inches apart connected to the battery for the seat heater which was measured to be 12.644V. Complete data from test found here.
Thermal Camera Image of Initial Seat Heater Design

Thermal Camera Image of Initial Seat Heater Design

Basic control of the power input to the heater was established using the purchased relay kit along with code created for the Arduino which is controlling the system.
P18347-Relay Control Functionality Demo

P18347-Relay Control Functionality Demo

User Interface

The LCD shield kit purchased over break was inspected for damage and assembled. Once assembled Functionality was verified using the code provided by the manufacturer. Initial decision to use the push buttons built into the shield has been revised; instead, large push buttons similar to those found on a late 80's arcade game will be implemented.
P18347-Push Button Input Functionality Demo

P18347-Push Button Input Functionality Demo

Bill of Materials

The below document shows the current status of the Bill of Materials. The status of the items are color coded. Green represents items that the team has acquired, yellow stands for items that the team has ordered, but has not yet received, orange stands for the item is known and sourced, but the team is waiting to order, and the red stands for the item not being sourced or decided on yet.

Financial Update

MSD II Phase II Financial Update

MSD II Phase II Financial Update

We have continued to update our BOM and a Purchase order checklist (POC) accordingly. A separate finance sheet is maintained and updated, keeping track of all expenses along with each purchase made along with date and price of item. 90% of the items in the BOM have been ordered and rest 10% pending on certain decisions at this point of time.

Risk and Problem Tracking

Problem Tracking Document

Problem Tracking Document

Plans for next phase

MSD II Phase III Schedule

MSD II Phase III Schedule

The teams three week plans for phase three of the project can be found at the following: P18347 MSDII Phase III Three Week Plans


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