P19361: Optoelectronic Guitar Pickup
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

The team plans on completing the detailed design of the optical guitar pickup. All parts should be on order, or prepared to be ordered, and the mechanical design should have a timeline as to how long it will take to make. A guitar routing plan will be made to ensure accuracy when cutting into the guitar. The MSD II plan will be completed by the time of our presentation, which will cover what needs to be done next semester.

This phase, the team completed prototyping and testing of our reflective sensor placement. From this, the team determined the sensor had to be moved closer to the strings from the design from last phase. The transmissive emitter was also changed due to needing to be further away from the sensors. The designs were updated to fit these new findings. A Bill of Material was completed for the parts included in our current design. An MSD2 schedule was created to help plan for the upcoming build process.

Prototyping and Testing

Due to the distance limitation of the QRE1113, testing was performed to see how far away the sensor could be from the strings and still get a good signal. The data sheet specifies a distance 5 mm is the max distance for the sensor to detect signals. This was tested by following the same steps to the Reflectivity of Strings feasibility performed last phase, with the added step of measuring the distance of the sensor from the strings. The results showed that after 5 mm, the signal amplitude dissipates significantly. The mechanical design from last phase had the sensors 12.7 mm, thus a redesign was necessary.

Following the results of this test, the team tested the transmissive design with the QRE1113 receiver at 5 mm and the emitter varying from 5 mm to 10 mm. The design worked best at 5 mm apart for each, however this is too close for the design to work properly. The team switched out the QRE1113 emitter with an infrared LED, and the sensor worked past 10 mm. Due to this, the transmissive electrical designs were redesigned with the new infrared LED included and the transmissive mechanical designs were redesigned with the new sized infrared LED and the updated distances.

Drawings, Schematics, Flow Charts, Simulations

Reflective Design: Electrical

Reflective Sensor Electrical Design

Reflective Sensor Electrical Design

This design is based on the Sparkfun analog line sensor board and previous revisions of the optical pickup project. The resistor values from the Sparkfun board were used, and a trim-pot will be used on the receiving end to allow fine tuning of the signal level at the input. These values are not final and will be tested.

Reflective Design: Mechanical

Reflective Assembly

Reflective Assembly

Reflective Adjustment Assembly

Reflective Adjustment Assembly

After further testing, we came to the conclusion that the QRE1113 sensor could not be under the pickguard, as it did not produce a usable signal past 5mm away from the strings. Since the adjustment mechanism could not be underneath the pickguard, we had to scrap the screw/spring arrangement. The set screw/spring arrangement needs to be under the pickguard so playing does not interfere with the placement of the sensors.

The slide track method was determined to be the method to move forward with, since normal playing will not affect the adjustment. The slide track adjustment method uses a set screw that can be cracked open to adjust the position of the sensor transversely to the strings, and then re-tightened to set the position.

Transmissive Design: Electrical

Transmissive Sensor Electrical Design

Transmissive Sensor Electrical Design

Although we were initially planning to use the same QRE1113 IR transceiver for the emitter of the sensor design, when we tested two QRE1113 chips in a transmissive configuration, the sensors did not have enough range to produce a good signal. The design has been modified to include a normal IR LED (p/n TSAL4400), which was tested and has better range.

Transmissive Design: Mechanical

Transmissive Assembly

Transmissive Assembly

Since we are using the reflective sensor as the photodetector, the bottom adjustments are the same as the reflective arrangement. A removable bar is added above the strings to hold the LED's. This bar uses an L bracket with two set screws to allow for adjustment transversely to the strings, along the strings, and to and from the strings.

Bill of Material (BOM)

Preliminary BOM. We still need to go through David's board to set up a full list of electrical components, and some mechanical parts may change in size slightly
Guitar rout

Guitar rout

Test Plans

Test plans are being developed for the engineering requirements. The current test plans developed so far are shown below.
Test Plans

Test Plans

These test plans will be finalized in MSD2, per the MSD2 schedule created by the team. For more information on the current test plans, see this excel sheet where the information is being edited.

Guitar Routing Plan

Guitar rout

Guitar rout

Guitar rout schematic

Guitar rout schematic

The routing will consist of connecting the bridge humbucker rout to the control cavity, routing out a section for the board, 14 thru holes for locating pins, and four pilot holes for the wood screws that will attach the reflective assembly to the guitar. The routing will be done on a CNC mill in the Brinkman Lab

Risk Assessment

This is our risk assessment for this phase. There are no new risks comparing this assessment to last phase's assessment.
Risk Assessment

Risk Assessment

Design Review Materials

Include links to:

Plans for next phase

Preliminary Gantt Chart for MSD II

Preliminary Gantt Chart for MSD II

Individually, we each will complete our own specific tasks for the rest of the semester. This links to the individual task document, which details what each member of the team will be doing for the rest of the semester.


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