Preliminary Detailed Design
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:
- First draft of BOM
- Updates to feasibility analysis
- Schematic design for rigid PCB with preliminary layouts
- Schematic design of LED layer
- Mechanical solutions for legs, strap system, touchscreen mounting
- A test plan for all proposed design solutions
Updated Design ArtifactsThis 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,
Feasibility and Engineering Analysis
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.
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).
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.
Harness ConceptA harder harness concept was created as an alternative to using the strap design considered in the previous phase. Below is an image,
Drawings, Schematics, Flow Charts, SimulationsThis 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 BlockA 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 PCBThis 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 PCBThis 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)here.
- Connect all 3 selected speakers to the prototype board and evaluate performance of each different speaker
- Measure dB output to confirm satisfaction of ER (75-85 dB)
- Main Rigid PCB
- Probe critical outputs from power block to confirm correct amount of power is being supplied to subsystems (ordering separate smaller board for power)
- Check trace continuity against layout for rigid and flex pcbs upon receiving
- Apply input power to board and check power/ground lines for each chip/IC
- Solder in components one subsystem at a time and verify workings
- LED Rigid/Flex PCB
- Test both horizontal and vertical traces to see which one is better.
- Test to see if rigid part of PCB is too big.
- Test to see if noise will cause issues in either design.
- Closing Contraption
- Test user can easily open and close Martone without damaging body
- Test Martone does not separate in two halves easily when flipped upside down and move around
- Test user can change legs from insert to horizontal position
- Test user can play in vertical position without any adverse effects
- Test Martone stands stationary when placed horizontally
- Test Martone does not knock over when played horizontally
- Test user can change and tensions strings easily
- Test strings stay tensioned after play
- Test touchscreen responds to user input
The Test Plan document can be found here.
Design Review MaterialsThe presentation for this phase can be found here
Notes from Review
- From Juan
- The current design solution for the legs does not
meet the vertical requirement. The instrument should
be stable on its own in vertical position.
- Supporting with shoulder makes it difficult to play the top notes.
- The harness concept looks functional but not
cool. It also needs to be something that is easily
carried. It is more important for the harness to
support the instrument for standing play though than
to just support it in general.
- It might be necessary to sacrifice some of the requirements for this to work.
- We may have to replace some of the harder parts of the harness with straps.
- For concept generation, we should consider using Teensy 4.0 over 3.2 for the speed it offers with little difference in cost.
- The current design solution for the legs does not meet the vertical requirement. The instrument should be stable on its own in vertical position.
- From Ken
- Discussion with Juan should take place to make sure that performance can be measured when using the new mounting technique vs old.
- BOM should take into consideration the labor cost for Juan in the future.
- The planning should include at least 3 mitigation actions for the risks presented.
- Words like "research" and "brainstorm" should be avoided in planning.
- For the Touchscreen Fastening, using 2-sided tape might be an issue due to changing thickness overtime.
- Add labor and other costs (assembly) to BOM.
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.