P16551: Observer Calibrator
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Subsystem Design

Table of Contents

Team Vision for Subsystem-Level Design Phase

During this phase of MSDI, we plan to expand on the functionality of the subsystems which comprise the Observer Calibrator.

We were able to develop a schematic which describes the circuits used to power each LED. This was accomplished by first narrowing down our choices of LEDs and converging on a solution to provide the requisite luminance levels for the device.

Ben began work designing the integrating spheres for color mixing of each side of the Observer Calibrator.

Lastly, preliminary flow charts were created to describe the software program flow and the testing process for the critical path of this project: achieving proper luminance levels out of the LEDs.

Feasibility: Prototyping, Analysis, Simulation

We did a proof-of-concept test to illustrate how we will control the LEDs for the Observer Calibrator. The test uses an LED, a transistor, two resistors, and a function generator. The function generator is used to create a square wave with varying duty cycle, in order to demonstrate controlling the LED intensity with Pulse Wave Modulation. The video can be viewed here.

We have begun narrowing down solutions for observer ergonomics. Below is the concept selection for this subsystem. The stand height should be adjustable by at least 5.4 inches, from the criteria set in the Wickens Table of Anthropometric Data.

Stand Concepts Considered

Stand Concepts Considered

Stand Concept Selection

Stand Concept Selection

Drawings, Schematics, Flow Charts, etc.

Electronics Design

Below is a schematic developed to describe how we will power the LEDs.

Schematic of LED Control Electronics

Schematic of LED Control Electronics

Since luminance is vital to the proper operation of the Observer Calibrator, we have identified a detailed test plan below:

Luminance Test Plan

Luminance Test Plan

Mechanical Hardware Design

We began designing the housing structure and integrating sphere for the Observer Calibrator. Below is a CAD drawing of the housing strucure.

Housing Drawings

Housing Drawings

We may be creating the integrating sphere ourselves, so below is a CAD drawing of the integrating sphere.

Integrating Sphere Drawings

Integrating Sphere Drawings

Below is an illustration of how the spheres will sit inside the housing.

Combined Integrating Sphere in Housing

Combined Integrating Sphere in Housing

Software Design

We have refined our anticipated use cases, and simplified them for the purpose of designing the researcher's software-side interface.

Refined Use Cases

Refined Use Cases

A preliminary example of the flow of our software is shown below.

Software Flowchart

Software Flowchart

Bill of Materials (BOM)

Below is a Bill of Materials for the critical functional blocks of the Observer Calibrator. This BOM will be updated as we converge on solutions for mixing chambers, observer ergonomics, and device mounting. The editable file is located here

Bill of Materials

Bill of Materials

Risk Assessment

Below is the relevant update we have added to our customer requirements in this phase.

Updated Customer Requirements

Updated Customer Requirements

We have updated our risk assessment to include the possibility of LEDs burning out or not providing enough luminance. Below are the risks we believe to be the highest priority and urgency.

Updated Risk Assessment.

Updated Risk Assessment.

The live risk assessment document can be found here.

Design Review Materials

The slides for our Subsystem Design Review can be downloaded here.

Plans for next phase

Next week, we plan to further refine our detailed design. We would like to order the LEDs we selected to test their luminance output. Once we have confirmed they will work, we will begin designing a mounting system for the LEDs.

After that, we will work on designing eyepieces for the observer, and further define ergonomics.

Then, we will be working on a more detailed description of the software flow and interface between the Arduino and the host computer.


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