P19330: Computer Chassis Cleaner

Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

Teams Plan:

Tasks accomplished:

Prototyping, Engineering Analysis, Simulation

Airflow Models

Branching Static Divider - divide main flow into smaller sub-branches to provide a field of air flow in the inner chamber.

Front View public/Photo Gallery/PDDR/Branch Proto 1.jpeg Rear View public/Photo Gallery/PDDR/Branch Proto 2.jpeg

Intake Manifold - Dynamic control of air flow with the use of valves. This will take the airflow supplied by the shop vac and enable the system to divert it when and where it wants.

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From these models, they were simplified and a 7" 1/2" OD tubing was connected to showcase what one 'trunk and branch' would look like. This was then placed into CFD software to try to gain more understanding on our flow parameters.

public/Photo Gallery/PDDR/Intake Proto Simulation.jpeg

ME Analysis

Due to limited knowledge of flow parameters, a MatLab code was generated to help in testing and simulation. However, once we found out the parameters generated by the code, we realized that due to supersonic flow the equations and assumptions used are incorrect and invalid for our situation. This is further discussed in feasibility and will serve at a limiting factor in our design work.

Live document version here

Feasibility: Prototyping, Analysis, Simulation

The Valve Controller Chips has limits as to how much current it can sink based on Duty Cycle and the Number of loads it is driving. This was analyzed using the following graph from T.I.'s TPL7407L Datasheet. Due to this, and the fact that the current chosen valves require 350mA per valve, one drive pin from the controller will not work. In the Schematics of circuit board you will see that each valve is controlled by 2 drive pins of the Valve Controllers which can handle the current load.

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From the mechanical side of things, our largest feasibility concern is all the unknowns when it comes down to the air flow through the system. Due to rough calculations, we found out that airflow will be at supersonic speeds in the system and current knowledge from the team is limited to sub-sonic flow. Also, if we are not able to branch our air flow into a substantial number of branches, we will not be able to cover the large area of the inner chamber with enough nozzles to have an effective cleaning flow. [The arrow shows the size of 1 branch/nozzle, and this shows the shortest side which is 2.5-3 times smaller than the largest side.]

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Consultation of SME's and further research into supersonic flow is required before finalized design and budgeting. Due to the limited time frame for MSD 1, this is the largest concern at this time.

Drawings, Schematics, Flow Charts, Simulations

Electrical Block Diagram

  1. Updated Block Diagram of the Electrical System is here. A 15 Amp Relay was added to the AC side of the system and the Temperature and Humidity Sensors were removed.

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The PCB Schematics are below. They are still in progress. Schematics


The Board layout is in progress in parallel with the schematics. The current design if 4 inches by 6 inches. It is four layers. All connections should be made easily but nothing is connected at the moment. Currently just working on placement until the schematics are complete.

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User Interface

Due to the elimination of sensors from the system, the need for error messaging is eliminated. Therefore the 7-segment display was removed to reduce cost and simplify the design. Below is the current concept for the User Interface. It has one large Blue button which also has an LED to indicate the system is powered on. It will also have a smaller red LED which can notify the user that the door is open or if another problem is detected by changing how the LED is illuminated, (Blinking or steady).

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Enclosure Designs

Two designs were created based on the final concept chosen based on use scenarios.

Design 1 is with the scenario of the enclosure itself being attached via the luggage style of a handle and caster wheels attached to the bottom with a cover opening from the top.

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A color code is used to differentiate the different elements involved in the interactions between both the internal and external frames.

The enclosure in both designs is going to be composed of two separate frames with the external frame being the main support for an internal frame which will contain the computer.

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The schematic below is the same enclosure with the cover for the internal frame.

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To explain the interactions some of the different elements involved:

Design 2 is going to be placed on a flat top surface such as a cart where the door will open from the side to slide the computer in.

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The same color code will be used for the design of this setup as well.

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Some changes compared to design 1:

The document for both schematics can be found here

Of course, the final design will be chosen by the customer in the Phase end review.

Bill of Material (BOM)

Electrical Bill of Materials

Electrical Bill of Materials with all known materials. Miscellaneous Circuit Board Components will be added to the BOM after Circuit Schematics and Board Layout are complete. These items include (Surface Mount Resistors, Capacitors, Additional Connectors). Wiring is also not included at the moment. This will be added during the next phase.

public/Photo Gallery/PDDR/BOM_Electrical.JPG

Live Document for Electronics BOM here

Mechanical Bill of Materials

Not certain of final design or materials

Test Plans

Mechanical Test Plans

Test for External Width and Depth


Test for Internal Volume


Other test plans include:

Live document for Mechanical Test Plans here

Electrical Test Plans

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The Circuit Board will also be tested while the circuit board is being built and populated. All Circuit Board functionality will be tested individually. Once the Schematics are finished, a detailed PCB testing procedure will be written.

Live document for Electrical Test Plans here

Design and Flowcharts

A high level concept of how the code will function on the Microprocessor is below. More detailed code flowcharts will be developed once discussion over the best cleaning cycle would run. Meaning controlling which valves and when still needs to be discussed but this current flowchart describes the higher level how the system works.

public/Photo Gallery/PDDR/Code_FlowChart.png

When considering the mechanical challenges needed for operation of the enclosure, we went back and modified our first ME flowchart to include detail of what we need to accomplish. For here, the hardest complication is that we still do not fully understand the airflow through the system and this is impacting design and budgeting.

public/Photo Gallery/PDDR/ME_FlowChart.jpg

Risk Assessment

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Live document version here

Design Review Materials

Plans for next phase

Mechanical Plans for Next Phase

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Electrical Plans for Next Phase

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Plans for Everyone

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Full Current Schedule here

Individual 3-Week Plans

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