Detailed Design

Team Vision for Detailed Design Phase

Summarize:

• What did your team plan to do during this phase?
  • Finalized design of system
  • Finalized bill of materials
  • User interface components ordered
  • Test Plans written
• What did your team actually accomplish during this phase?
  • Developed more complete design of system
  • Ordered components for user interface, control, and motor subsystems
  • Wrote test plans for user interface subsystem

User Interface Subsystem

Microcontroller Configuration

2 microcontrollers (1 for student input, 1 for teacher input and device)

• Student Input
  • Arduino
  • Need Bluetooth
  • Low power

• Teacher Input and device

  • Need bluetooth

  • Need screen output

  • Need many pins

  • Raspberry pi

Team decided to plan on using 2 microcontrollers

Determination of Programming language

Python was chosen as the programming language for the teacher input as it is the most familiar and would be the easiest to work with.

C was chosen as the programming language for the student input as it can run on arduinos and teensys and allows for low power and fast execution.

Design of Teacher Input Screen

The teacher input screen was designed to allow the teacher to be able to remotely control the device along with the student, stop the student from being able to control the device if necessary, input the size of drawing area, and select tools for drawing. The design can be seen below:

Python code was written to emulate the design of the teacher input screen shown above. The teacher input user interface designed in Python can be seen below:

Student Input Parts

Buttons:

• Ablenet( https://www.ablenetinc.com/switches/)
  • Jelly Bean
    • $65.00
    • 2.5" diameter
    • Removable cover
    • 3.5mm barrel connector
  • Big Buddy Button
    • $65.00
    • 4.5" diameter
    • Smooth top
    • 3.5mm barrel connector

Joystick

• Adafruit small arcade joystick
  • https://www.adafruit.com/product/480
  • $14.95
  • 8 direction
  • 4 switch output
  • Top can be removed

Microcontroller

• Arduino Nano 33 IoT
  • Has Bluetooth and Bluetooth low energy connectivity
  • Input voltage of 3.3V
  • 14 pins
  • Jameco ($19.95)
    
    • https://www.jameco.com/z/ABX00027-Arduino-Arduino-Nano-33-IoT-without-Headers_2304695.html

Student Input Options

The wheelchair table is 24" wide and 12" deep.

Using Big Buddy Buttons the buttons would have to be close together but would have a large area to hit.

Using Jelly Bean buttons the buttons could be spread further apart but would have a smaller area to hit.

Updated Microcontroller Benchmarking

The microcontroller benchmarking from the previous phase was trimmed down to focus on the most important features to better facilitate choosing which microcontroller to control each of the subsystems. The main features being looked into were Bluetooth connectivity, low power, high number of I/O pins, and a display port.

Block Diagram of User Interface

Motor Subsystem

Initial Motor Specification Requirements

Control Subsystem

Benchmark stepper drivers

Control Subsystem schematic

Power Subsystem

Updated Power Subsystem Block Diagram

Updates:

• AC/DC Converter selected with output of 5V and 12V. The 5V output will be easier to step down to 3V for the motors. 
• A linear regulator is used instead of the dc/dc converter for the motor voltage to ensure 3V is provided.
• The servos for the gripper and z-axis are given 7.4V. The input range on the servo is 4.8V to 8.4V. The input voltage will be determined with testing. An adjustable buck dc-dc converter is used to adjust the voltage.
• The Arduino Nano will be powered by a lithium ion power bank.
  • The power bank can be recharged through a wall adapter and USB cable.
  • This solution allows for easy charging and replacement of the power bank if needed.

Finalized Power BOM

Gripper Subsystem

Extra jaws were added to further support the tool and standoffs were added to space the jaws out from one another. Servo model and gears have been updated to specs from off the shelf components. Hardware has been added. 

Belt Subsystem

The belt system was updated to include 2 belts to move the gripper and slide assembly.

New Parts Needed:

Mechanical Subsystem

Bill of Material (BOM)

Updated BOM

• Need more materials than originally anticipated.
• Large, easily pressed buttons are more expensive than anticipated.
• We'll request a budget increase at the beginning of MSDII with our finalized BOM.

Document: here

Test Plans

Live Document: https://docs.google.com/spreadsheets/d/1_IZcNNnW0dwpgoJAZ-F0mmnLqIqh75EQA9Q7DGl4pTg/edit?usp=sharing

System Design and Flowcharts/System Block Diagram

High Level System Block Diagram

Risk Management

Design Review Materials

Detailed Design Review Notes & Actions

Plans for next phase

• First 2 Weeks of MSD II
  • Review and Finalized the BOM
    • Order final components
    • Submit Budget Increase Request
  • 3D Print Gripper and Cup to test interaction
  • Start Assembly 
  • Test the Motors
  • Gather the components we need for testing

• Individual Phase Plans
  • Andrew Pasek
  • Allison Morgan
  • John Owens
  • David Nwokolo
  • Dylan Lebedin