P20395: The Martone
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

Goals for Phase 3: Preliminary Design:

In this phase of MSD1, the team worked on producing preliminary designs for all relevant concepts selected for the next iteration of the Martone. This includes schematic diagrams of circuitry, technical drawings of mechanical designs, and any additional relevant diagrams/charts to the design. Ultimately, the final goal for this phase was to have a basis for the final design of the Martone, so that in the final phase of MSD1, the design for the new Martone could be finalized.

Phase 3 Accomplishments:

Updated Design Artifacts

This phase, communication with the customer has led to new features to be considered in the final design of the Martone. The most notable changes included a dedicated on/off switch on the instrument body, a dedicated volume control mechanism, and the inclusion of a proximity sensor within the Martone. The on/off switch came as a result of the instrument currently only being capable of activating and deactivating electronics by plugging and unplugging the Martone. The volume control mechanism was important because the Martone's volume can only be adjusted by accessing the electronics within. Finally, inclusion of a proximity sensor was a personal choice by the customer. These changes were captured in the customer requirements and engineering requirements which are shown below,
Updated Customer Requirements

Updated Customer Requirements

Updated Engineering Requirements

Updated Engineering Requirements

Feasibility and Engineering Analysis

Martone Dimensions

Martone Dimensions

The Martone outer body dimensions are set by the customer at an ellipse of width 3 inches and a height of 1.75 inches. The assumption is the minimum wood thickness that could support the body or be manufactured is 0.15 inches in thickness. This assumption comes from the previous edition of the Martone that was CNC'd successfully to this shape. This assumption will need to be monitored carefully as features are added to the Martone. The first of which is the embedded touchscreen. The touchscreen dimensions were measured from the current Martone to be 2.1mm. This is subject to change as the LED layer will be redesigned, but this value will be used for now. The two options being pursued are embedding the touchscreen in the wooden top layer by thickening the section, or cutting a window and placing a malleable metal plate backing and supporting the touchscreen. The benefits of using the metal plate is the cross sectional area does not decrease, allowing for space for the components. However, it is not clear whether the rails could be CNC'd to the geometry shown below. In the next phase, expert analysis will be seeked and a design will be selected that allows for manufacturability.
Thickened Top Layer

Thickened Top Layer

Metal Plate in Body

Metal Plate in Body

Thin Rails

Thin Rails

Three methods of opening and closing the Martone for access to the components were identified: a regular hinge as seen in most doors, concealed hinges also known as barrel hinges, and a mortise and tenon joint combined with a magnet to hold the two halves together. The regular door hinge was not acceptable to the customer requirements as the user's hands would come in contact with the protruding tube that is inevitable with a regular hinge. The barrel hinges seemed promising as they come in miniature versions on the order of less than 10mm in diameter. However due to the elliptical shape of the Martone and the minimum distance between the two barrels, either the Martone cross-section would require a chamfer or rectangular extrusions would be required to house the barrel hinges.

Barrel Hinge

Barrel Hinge

Mini Barrel Hinge Superimposed on Elliptical Cross Section

Mini Barrel Hinge Superimposed on Elliptical Cross Section

Barrel Hinge Chamfer

Barrel Hinge Chamfer

Barrel Hinge Extrusions

Barrel Hinge Extrusions

The remaining option is to use magnets and a mortise and tenon joint. Using small magnets found on Amazon, and using them as the males for the joint, the concept was deemed feasible as it has a small footprint on the Martone body and can be placed at any location with little interference with the other electronics and mechanisms. Should the magnetic strength be too great or too little, the number of joints could be increased or the distance between magnetic rectangles could be increased.
Small Cheap Magnets Found on Amazon

Small Cheap Magnets Found on Amazon

Magnetic Mortise and Tenon Joint

Magnetic Mortise and Tenon Joint

Magnetic Mortise and Tenon Joint

Magnetic Mortise and Tenon Joint

Attaching the touchscreen to the body requires fixing the polycarbonate layer to the outer area of the ellipse. The current design wraps the polycarbonate into the surface on the inside of the top half of the Martone with two sided tape. It was considered whether a pin could hold the polycarbonate to the outer surface so as not to need to wrap the polycarbonate to the inside of the Martone. The idea being if the polycarbonate is wrapped inside it takes up extra inner space of the Martone and bellies the polycarbonate and may affect the touchscreen sensitivity. Assuming the electrode width is reduced by 0.4" from current dimensions and creating the bed of the touchscreen accordingly, there is just barely enough space to fit the smallest chicago screw posts found available on the internet. As shown in the drawing below, holding the polycarbonate along the long side of the Martone is not feasible with pins. The pins will need to either be on the long ends or a cover plate will be needed. Further manufacturing feasibility analysis is needed to determine whether a wooden window-like plate could be made to hold down the polycarbonate layer.
Chicago Screw Post

Chicago Screw Post

Space Allowed for CSP

Space Allowed for CSP

Regardless, even if the screw posts could fit in the space allowed by the rails of the body, the post heads would overlap onto the touchscreen and likely annoy the users hands as it traveled along the instrument length.
CSP Overlap

CSP Overlap

For the leg design, the current Martone design will be used with the improvement to the shape of the legs for a more aesthetic design. The legs will retract into the body maintaining an elliptical body shape. The legs will slide out on a metal rod and rotate down into a horizontal position. They will then rotate out and lock into an expanded position. The legs must allow for 0.45" diameter worth of cables to enter the extremities to connect the 1/4" jack, 1/8" jack, and the usb. The horizontal play position must be stable and stand freely. The design shown below utilizes the mini chicago screw posts to rotate the legs out. The material can be either wood (laser cut) or metal (CNC machined).

Legs Expanded

Legs Expanded

Legs Retracted

Legs Retracted

Legs Retracted

Legs Retracted

Space for Cable Connections

Space for Cable Connections

The tuners are to hold the strings in place and be easily adjustable for the user. This requires the attachment of the string to be accessible from the outside of the instrument. The difficulty with this is that most tuning pegs hold the string on the opposing side of the handle the user spins to tighten/loosen.

Common Tuning Peg

Common Tuning Peg

After some research, a banjo 5th string tuning peg was selected as feasible for the Martone application as it holds the string on the same side as the user's applied torque.
Banjo 5th String Tuning Peg

Banjo 5th String Tuning Peg

Another similar option is to use zither pins with custom made wooden handles to hold the guitar strings. This option is noticeably cheaper as zither pins run about $1 a piece vs $10-$50 for a 5th string banjo tuning peg. It also has the benefit of maintaining a wooden theme and the knobs can be designed to house the Martone/Brazenhouse logo. The zither pins have not been analyzed for geometric feasibility but will be pursued in parallel with the 5th string banjo string unless proven to interfere with the leg mechanism.
Zither Pin

Zither Pin

Harness Concept

A harder harness concept was created as an alternative to using the strap design considered in the previous phase. Below is an image,
Hard Harness Concept

Hard Harness Concept

To operate, the Martone would need to be designed with two rings/tubes inside of it that was securely attached to the frame. The instrument would then be placed on the harness by sliding the two rails through the tubes. Next, the instrument could be adjusted at any angle desired relative to the bottom and then locked in place by tightening the two joints that connect it to the harness. The major advantage of this system is the ability to have the instrument rest at many different angles relative to the body, making it easier to play in a vertical position. The disadvantages include being heaver, potentially less comfortable, and overall being less stylish than the strap system.

Drawings, Schematics, Flow Charts, Simulations

This section contains preliminary detailed designs for the electrical subsystems of the Martone. This includes main rigid PCB schematics/layouts, LED layer schematics/layouts, and any other relevant diagrams/simulations.

Power Block

A Component Level Diagram of Power block design is shown below. USB 3.0 inserts at the connector to supply power. The charge controller manages the charge voltage and current so that the LIPO 3.7 V battery is charged at an acceptable rate and voltage. A power switch controls the battery supply to the internal electronics of the Martone. A link to the some of the research/design documents can be found below. Among these documents are notes about the designs, small feasibility calculations, possible IC's and solutions, and notes on the design process. https://edge.rit.edu/edge/P20395/public/Phase%20III%20Documents/Power%20Block

A preliminary design for the USB 3.0/Charge controller circuit can be seen below. The selected charge controller chip has a programmable current that can be set by changing resistor Rprog's value. Please note that this circuit was previously set up for USB 2.0 and as a result can support 500 mA output charging current. This circuit will be modified in phase 3 to allow for 2 A charging current Ibat, which means the charge controller IC here will be swapped for a more appropriate IC.

Rigid PCB

This board holds the main electronics of the Martone, such as the micro-controllers, auxiliary integrated circuits, and the power regulation circuitry. The Eagle schematic and layout files can be found here.

Electrode PCB

This flexible board contains all of the electrode scanning footprints, as well as the routing to the FPC connector which will allow the electrode board to interface with the rigid board. The Eagle schematic and layout files can be found here.

Bill of Material (BOM)

A live document of the BOM can be found here.

Test Plans

The Test Plan document can be found here.

Risk Assessment

The Risk Assessment document can be found here.

Design Review Materials

The presentation for this phase can be found here

Notes from Review

Plans for next phase

In the coming phase our team will take the improved detailed feasibility in addition to the design work that has been completed at the end of this phase, and proceed with the design work for the electrical and mechanical systems. The goal for the end of the coming phase is to have these designs completed and verified by a third party, and have the fabricators/designers chosen. Upon agreement that all systems are correct and meet their specific requirements, both individually and combined, the designs will be sent out to order. Upon receiving the completed designs, the aforementioned test plans will be conducted on the appropriate design(s). A link to the team's 3-week plan document for the coming phase can be found here.


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