Preliminary Detailed Design
Table of Contents
Team Vision for Detailed Design PhaseDuring this phase, we ordered the materials we'll need to begin prototyping the Observer Calibrator. We planned to prepare a prototype circuit with the LEDs we will end up using, but were delayed due to an issue with the MSD ordering system.
During this phase, we also revised our Engineering Requirements, Test Plans, Design Drawings, and Software Plans in accordance with the information we gained from the last Design Review.
We began looking further into stands for the Observer Calibrator, but this is not on the critical path for our project.
Prototyping, Engineering Analysis
During this phase, we planned to prototype the LED array with the actual LEDs we will be using. Due to an issue with the MSD purchasing system, we did not acquire the LEDs in time. However, the prototype developed during the Subsystem Design phase can still be viewed here.
Drawings, Schematics, Flow Charts, Simulations
Below is an updated schematic for the LED array.
The above schematic was simulated again, and the updated simulation can be seen below:
From the schematic and simulations, we calculated the individual resistor values for each LED. This was necessary because of the different forward voltage and forward current specifications for the different types of LEDs. The selection of Resistor values is given below.
The CAD models of the integrating sphere have been updated, and are shown below:
The housing was redesigned with peg board, to allow easier mounting of the integrating spheres.
Bill of Material (BOM)
We have updated our BOM, and it now includes a potential stand and platform for the Observer Calibrator.
With this updated BOM, we mapped out our budget and compared it to the maximum budget allocation. This can be seen below.
A rough outline of our testing plan for the mechanical aspects of the Observer Calibrator is given below:
- Purchase possible elements and measure dimensions to see if part fits, examining schematic for certain components
- 3D print any designed parts if needed
- Make sure each designed component is ready to build prototype and to be tested by beginning of next semester
- Trouble shoot any possible problems
We identified the LED luminance as the critical component for this stage of design. Thus, we developed test plans for the LED luminance before and after creating the integrating sphere. We also added a test plan for the stability of the LED brightness. A link to the Requirements and Testing document, which contains more details on the proposed test plans, is given here
Details regarding the three phases of LED testing are given along the right.
- First, we will measure the luminance of just the LED array. From this test, we may need to adjust the PWM signal to move the maximum and minimum luminance levels.
- Second, we will measure the stability of the LED array. If this is not meeting requirements, we may have to adjust the power supply or LED array control circuits.
- Third, we will add the integrating sphere and re-do the measurement of the luminance, to ensure it still meets our requirements. If necessary, we will also re-adjust the PWM generator in software.
Design and Flowcharts
Below are screenshots from GUIDE, a tool used to create graphical user interfaces in MATLAB. We plan to use this for the researcher interface.
We also looked at some sample code for controlling the Arduino in MATLAB. This is shown below:
Last phase, it became apparent that we may desire to have a user interface for the observer, as well, for alternate use cases. The observer would be able to adjust the primaries in one LED array until they match. An example of a knob usable for such a situation is given below:
Below is a screenshot of our latest risk assessment. The risk assessment has not changed, but the due dates for some items have passed due to the delay in acquiring our LEDs. The live document is available here
Design Review Materials
The slides for our Preliminary Detailed Design Review can be downloaded here.
Plans for next phase
- Next phase, we will have the LEDs we ordered, and will demonstrate proper functionality in our prototype circuit.
- We will also acquire a sample of 3D printing material to test its compatibility with potential reflective coatings for the integrating sphere.