Table of Contents
Prototyping, Engineering Analysis, SimulationMechanical Design
P13323 Opto-Electric Guitar Model
Factor of Safety analysis for each mechanical component is on the left, and Von Mises plots for principal stresses in each component are on the right.
Guide BedImages show the guide bed being tested with an 8N tensile force being exerted on the strap surfaces per calculation for 3g's of retention force to the soundboard. Tensile force was derived from soundboard retention force and the angle of the straps where they connect to the guide rail.
Upper Sensor Mount (Photo-transistor)These show upper sensor mount being tested with an axial clamping load of 20N, enough to retain component and sensor when dropped from 1.5 meters. The lower sensor mount will not have the 4.69mm diameter hole in it, and will therefore be more resistant to deformation and failure than the upper mount.
Sensor Mounting PostImages here show the sensor mounting post being tested with an axial clamping load of 65N, enough to retain the mass of the component itself, and all components attached to it, when dropped from 1.5 meters.
Drawings, Schematics, Flow Charts, Simulations
System Block Diagram
All internally designed mechanical components are shown here.
Individual PDFs can be obtained for each component as well:
As well as PDFs for the purchased enclosure, set screws, and switches
Bill of Material (BOM)
Subsystems Test Plan
- Test in different lighting conditions
- Incandescent lighting
- Fluorescent lighting
- Natural light
- Test ADCs and routine speed
- Read in signal, then use LEDs attached to indicate when each process is complete
- Test DAC and filters
- Send test signals with frequencies both within and outside of the filtered bandwidth
- Use oscilloscope to observe output
- Send test signals with frequencies both within and outside of of the filtered bandwidth for each string
- Observe the output from each stage of each string with an oscilloscope when applying the test signals
- Test battery life by having someone play it until the battery quits
- Test functionality of the voltage regulator by attaching a variable power supply
- Alignment accuracy with repeated installation
- Screw vibration test
- Stripping torque
- Test effect of interaction with user interface on strap position
- Test strap position with the amp hooked up
Whole System Test Plan
- Hook up system to amp and play
- Play using analog processing
- Play using digital processing
- Conduct a blind test between analog and digital processing paths to see if a difference in sound can be detected
- Compare original signal to signal from amp for each path
- Have a test subject, someone who has no prior knowledge of the project, install and use to judge ease of use and quality
Risk AssessmentRisk Assessment PDF
- Risk items 11-20 are the updated risks based on the design
Detailed Design Review
- Can a relative level between harmonics be developed on the analysis?
- Scale MATLAB models to the fundamental frequency, then overlay input and output for comparison.
- How are we making use of these waveforms?
- Keep in mind, the microphone acts as its own low pass filter when recording.
- Are there defined ranges for filtering?
II. Block Diagram
- Increase font sizes to fill each block for readability.
- How much will the digital/analog switch interfere with the circuit?
- Trans-impedance amp fixes weak signals. Analyze and make measurements.
- Gain stage should be before ADC.
- Are there any results for sample and hold times for ADC?
- Op amp data sheet to determine initial variable resistor range.
- Make a standard resistor in series with variable resistor, rather than only variable resistor.
- Minimize current by making resistances in the K-Ohm range.
- Passive elements have tolerances (measure several and find closest.
- Define the variables.
- Boost converter.
- Need to test operation of amplifiers at 9V.
- What are the voltage requirements for power?
- Can we get op-amps down to ±5V?
- Easier option- off the shelf voltage integrator.
III. Needs and Specs
- Ballpark op-amp metrics, filter metrics.
- Select switch- be careful of interference.
- Define Sensors.
- Is there a predefined PSpice model from the manufacturer? Should import device model as sub-circuit.
- Send Dr. Patru part numbers and manufacturers.
- Will the light bounce off the string into the other sensors? Not with our mounting arrangment.
- Capacitance might be too high in the circuit.
- Phase shift in the analytical output is somewhere in the equations. Play with values and see about phase shifts in the simulation.
- To help find where phase shift is coming from, consult Dr. Bowman
- Maybe license limitations on programs because of student version?
- Look into HSpice- Dr. Bowman (better program).
- Is 144 pin DSP a necessity?
- Tutorials in SIMs building for SMD operations.
- Don't try to model analog.
- If we can sample and hold 2 ADCs at a time on the current micro controller, show this in pseudo code.
- Is there a known speed of every routine?
- Certain parts need to be done in assembly- identify these.
- Are there other 32 bit architectures? Same family but maybe smaller. Concerned about ADC resolution, some go down to 8, but are smaller.
- Breakout board availability and prices?
- Need trial FIR filter details and results.
- Optimize sensor placement with oscilloscope first time only? Yes, mechanical calibration will take care of positional misalignment after that.
- Think about electrical calibration process and how to make it easier.
- Velcro at each interconnect? Yes, with room to shift components for a custom fit.
- Pad under processor? Yes
- Pad under sensor unit? No, but can make one if need be.
VII. Risk and BOM
- Dr. Patru would like to recap with everyone before PCB design goes out.
- Might need an amp for photo transistor signal to transmit effectively. CAT5 cable a possibility for shielded wiring.
- No more than 4 layers for the boards.
- Would we require separate analog and digital boards?
- OSHPark- possible circuit board manufacturer.
- Solder mask and copies of PCBs for cheap advanced circuit.
- We can cut the board in half if we order more than one circuit per board.
- Should integrate as many test points as possible (micro testing).
- On the macro level, how does it compare to other products?
- Show and document the test structure (in final documentation).