October 27th- Class Canceled; Items for Next Week

Questions for Students:

1. What project are you planning to work on?  Laser Harp? Optical Music Box?
   
   
2. What is the Minimum Viable Product? (https://www.engineeringdesignworkshop.com/minimum-viable-product.html )
   
   
3. Who is working on the project? Students are encouraged to work in groups
   
   
4. Download the Arduino IDE ( Integrated Development Environment) and install it on their own computers.  Watch the intro video at https://youtu.be/zfp0IJoXcFg

5.  Bring laptops to next week’s class.
   
   
   
   
   For next week:

Review Project Plans and needed parts, such as:

• Laser Diodes
• IR Sensors
• Microcontroller
• MIDI Board
• Speakers
• Power Supply
• Paper transport for Music Box
• Laser Harp Frame

Lab activities: 

• Sensor lab: 
• IR Reflective sensor- how they work; adjustments (https://eca790.blogspot.com/p/building-custom-optical-music-box.html )
• Laser Diodes + Photo-resistive sensor- how they work
• MIDI (https://eca790.blogspot.com/p/midi-musical-instrument-digital.html ) 
• Intro to Arduino- Blink, Analog Read

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AI-generated Course Overview & Prerequisites

• Target Audience: Freshmen
• Duration: 4 sessions (approximately 90–120 minutes each).
• Core Concepts: Voltage dividers, analog sensing, sound generation (tone() vs. MIDI), conditional logic, and physical alignment.
• Hardware Kit (Per Team of 2):
• 1 × Arduino Uno (or Nano) + USB cable
• 1 × Half-size or full-size breadboard
• 4–6 × 5V 650nm Red Laser Diode modules (Class 2 / Class 3R, 5mW maximum)
• 4–6 × Light Dependent Resistors (LDRs / Photoresistors) or LDR modules
• 
• 4-6 IR line sensors
• 
  
• 4–6 × 10kΩ Resistors (for voltage dividers)
• 1 × Passive or active piezo buzzer (or 3.5mm audio jack for external speaker)
• Jumper wires & cardboard/foam-board/laser-cut wooden frame

Session-by-Session Instructional Sequence

1.Optical Sensing & Safety Fundamentals: 

• Prerequisite safety check: Class 2/3R eye safety rules must be briefed first.

• Objective: Understand how an LDR detects light intensity changes and wire a stable voltage divider circuit.
• Safety Briefing: Never look directly into the laser beam or point it at reflective surfaces; ensure all laser modules are powered off until mounted.
• Hands-on Task:
1. Build a voltage divider with a single LDR and a 10kΩ resistor connected to pin A0.
2. Upload a simple analogRead() sketch and observe ambient light values via the Arduino Serial Plotter.
3. Aim a handheld laser pointer at the LDR to determine the "hit" threshold vs. "blocked" threshold.

2.Sound Generation & Single-String Prototype:

• Objective: Translate an interrupted light beam into a distinct musical note.
• Hands-on Task:
1. Wire a piezo buzzer to digital pin 8.
2. Introduce Arduino's built-in tone(pin, frequency) function.
3. Write a threshold conditional statement:
   
   Arduino Code sample:
   
   if (analogRead(A0) < threshold) {
     tone(8, 262); // Middle C
   } else {
     noTone(8);
   } 

Test interrupting the beam with a finger to verify immediate response latency and calibrate ambient light sensitivity.

3.Scaling to Multiple Strings & Code Architecture:

• Objective: Scale the circuit from 1 to 4–6 strings without writing repetitive code.
• Hands-on Task:
1. Duplicate the LDR + 10kΩ voltage divider across pins A0 through A4.
2. Refactor code using arrays for pins and musical frequencies:
   const int sensorPins[] = {A0, A1, A2, A3};
   const int notes[] = {262, 294, 330, 349}; // C4, D4, E4, F4

Implement an automatic calibration routine inside setup() that reads ambient levels for 2 seconds to calculate dynamic trip thresholds.

4.Chassis Integration & Final Performance:

• Objective: Mount components to an enclosure, align optical paths, and polish interaction.
• Hands-on Task:
1. Assemble a cardboard, wood, or 3D-printed C-frame.
2. Mount laser diodes on the top arm and LDRs inside recessed channels (baffles or heat-shrink tubing) on the bottom arm to shield them from ambient room lighting.
3. Align laser dots to photoresistors and test multi-beam chord or melodic playback.
4. Extension Option: Swap the piezo buzzer for a MIDI-over-USB library to trigger digital instruments inside software like GarageBand or Ableton Live.
   
   Common Pitfalls & Troubleshooting Checklist
• Ambient Light Interference: Overhead fluorescent or LED lighting can trigger false positives. Wrap heat-shrink tubing or black paper collars around each LDR to create a narrow field of view.
• Beam Misalignment: Fixed frames flex. Ensure the laser mounts have slight mechanical tolerance or set-screws for manual beam adjustment.
• Monophonic Limits of tone(): Arduino's standard tone() function can only generate one frequency at a time. Remind students that simultaneous multi-beam playing requires MIDI output to an external synthesizer or a multi-channel audio shield.

 

October 20th- Narrowed Project Choices

October 13th- Creating a meaningful gift; Musical Instruments

Laser Cutting and Engraving Workshop

Participants are learning how to design and vectorize drawings to create custom acrylic inserts for Aurora Bear bases using a laser cutter.

Design Principles

Ed Moriarty emphasized the importance of creating meaningful projects rather than simple decorative items. The goal is for participants to act as agents in their own design process, potentially creating gifts for others. The project is presented as a metaphor for a career at MIT, emphasizing the importance of being an active agent in one's own design process.

Technical Guidelines

• The current task involves designing an insert for an Aurora Bear base made of acrylic. Designs must fit within the dimensions of the Aurora Bear base
• Participants should avoid designs that hang over the edge too much to prevent tipping.
• Using two highly contrasting colors (e.g., black and red) is essential for the vectorization process in Adobe Illustrator.
• A "stencil font" approach is recommended to avoid small pieces of acrylic falling out during the cutting process.

Laser Cutting Process

Lars explained the transition from pixel-based drawings to vector-based paths that the laser cutter can follow.

Vectorization and Settings

• The process involves turning images into lines with specific start and end points( scalable vectors).
  
  
• Two distinct types of lines must be differentiated: cutting (the silhouette/outline) and engraving (surface details).
• Differentiation is achieved by assigning different colors to different tasks.
  
  
• Machine parameters such as power, speed, and pulse rate are adjusted based on material thickness (e.g., 1/8 inch acrylic vs. 1/8 inch birch).
  
  
• High power at slow speeds can be used for cutting, while different settings are required for etching or engraving.

A distinction is made between cutting (the silhouette/outline) and engraving (surface details).

•  Participants are cautioned against designs with "holes" that could cause pieces of acrylic to fall out during the cutting process.
  
  
• Total internal reflection allows light to travel through the acrylic, making scratches or engravings visible when illuminated.

Execution Steps

1. Draw a design on paper using contrasting colors (like red and green or black and red), using Sharpies.

Importing Documents into X-tool with manual SVG editing:

xTool supports color-based tracing directly without requiring complex vector editing. You have two main approaches depending on your machine model and how much control you want over the final cut.

Method 1: "Process What You Draw" (Offline)

Requires a camera-equipped model like the xTool M1.

You can bypass the software entirely if you use standard Black and Red markers.

1. Draw your design directly on your material or an A4 piece of paper. Use a Black marker for lines you want to engrave, and a Red marker for the outlines you want to cut.

2. Place the material inside the laser cutter directly under the camera.

3. Press the physical start button on the machine.

Verification: The laser head will move to scan the bed, recognize the specific colors, and automatically execute the job without needing to be connected to a computer. 

Method 2: "Layering by Color" (Using xTool Creative Space)

Works with any xTool model.

If you want to use more colors or manually verify the cut parameters before firing the laser, use the XCS software's built-in color separation tool.

1. Draw your design using solid, distinctly different colored Sharpies (e.g., Blue, Red, Green).

2. Import a photo or scan of the drawing into xTool Creative Space (XCS).

3. Select "Trace Image" from the image settings panel. 

4. Toggle "Layering by color" to ON, adjust the Fuzziness threshold so the lines look crisp, and click Save.

Verification: Your design will appear on the canvas grouped into separate vector layers based on color.

5. Assign processing modes: Click each color's layer in the right panel and assign it to Score, Engrave, or Cut. 

WARNING: Auto-Trace Failure Risks

Ensure your drawing paper or material is completely flat. Creases, uneven shadows, or poor lighting will cause the camera to misread the colors, leading to failed cuts or the laser firing in unintended areas. Use thick, high-contrast lines and avoid overlapping different colors.

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Gemini 4 Argon can create an SVG from a photo of a drawing, and it can do so in two distinct ways depending on whether you need a clean conceptual reconstruction or an exact pixel-accurate trace. 

Because SVG files are strictly text-based XML code (<svg>, <path>, <circle>, etc.), Argon’s combination of visual-spatial reasoning and code execution makes it uniquely suited for this.

Method 1: Algorithmic Tracing via Code Execution (Best for Exact Contours & Laser Cutting)

When you enable Code Execution (standard in the Gemini interface and Google AI Studio), Argon does not just "guess" the coordinates visually. Instead, it writes and runs a Python script in its sandbox environment to process your uploaded photo directly:

1. Image Preprocessing: It uses libraries like OpenCV (cv2) or Pillow to remove shadows, adjust contrast, and convert your photo into a clean binary (black-and-white) threshold image.

2. Vectorization: It extracts the exact mathematical contours or skeletons of your lines and converts them into SVG <path> data, outputting a downloadable .svg file.

3. Why this matters for fabrication: If you are converting a marker or pen drawing for a laser cutter or CNC router, you can explicitly instruct Argon in how to process the lines:

• Outline Tracing: Captures the thickness of the pen stroke (creating closed double-line shapes suitable for engraving/filling).
  
  
• Centerline Tracing (Skeletonization): Reduces thick marker lines down to a single mathematical path down the center of the stroke, preventing a laser cutter from passing over the same line twice.
  
  
• Color Grouping: If your drawing uses multiple ink colors (e.g., black for cutting, red for scoring, blue for engraving), Argon can segment the image by HSV color ranges in Python and export an SVG with color-coded layers.

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Project Brainstorming and Technical Discussion

Participants brainstormed various technical project ideas ranging from musical sensor devices to health monitoring and interactive art.

Project Concepts

Discussion of Mechanical Music Boxes

Musical Sensor Device

• A device was proposed using a row of sensors to detect dots on paper (such as adding machine rolls or sheet music).Challenges regarding the mechanical construction and the use of adding machine rolls for sheet music are raised.
  
  
• The team considers using AI to read musical scores by scanning dots on paper.
  
  
• The system would use an Arduino to send MIDI signals to a shield, allowing the user to trigger specific notes like a tuba or C sharp.
  
  
• Ed discussed the technical implementation using photoresistors and voltage dividers, noting that reflectance sensors could detect light and dark patterns by measuring voltage drops. The distinction between reflectance sensors, which bounce light off a surface, and break beam sensors is clarified.

The SparkFun Musical Instrument Shield is an easy way to add great sounding MIDI sound to your next Arduino project. This board is built around the VS1053 MP3 and MIDI codec IC, wired in MIDI mode. Simply connect a speaker/stereo/pair of headphones to the 1/8" stereo jack on the shied and pass the proper serial commands to the IC and you'll be playing music in no time!

The VS1053 contains two large tonebanks including various piano, woodwinds, brass, synth, SFX and percussion sounds. The shield is also capable of playing several tones simultaneously (maximum polyphony of up to 31 sounds!). Take a look at our example code to get an idea of how easy it is to add musical zest to your next Arduino gadget.

Interactive Reading Tool

• A concept was discussed for a handheld device or camera-based tool that could identify a book and allow users to interact with its content via AI.
  
  
• The goal would be to point at a page—such as a specific edition of Shakespeare—and receive digital information or audio readings.

Health and Personal Projects

• An interest was expressed in health monitoring technology similar to a Whoop Activity Tracker device, focusing on heart rate, ECG, and stress monitoring.
  
  See work on wearable healthcare technology by MIT  professor Canan DagDevirin
  
  
• Another idea involved creating a meaningful, low-bandwidth communication device for a family member, such as a wall-mounted object that changes color to signal moods or status.
  
  Feel Emotion Sensor
  
  
•  A discussion occurs regarding creating a personalized gift for someone's father, such as an artistic watch or a meaningful piece of decor.

• Ed emphasized the need to define the "magical part" of a project and identify the target audience before proceeding.
  
  
• Questions remain regarding the mechanical feasibility of moving sheet music through a sensor array and how to best integrate AI into the reading pen concept.

Chrome Music Lab
https://musiclab.chromeexperiments.com/ 

Why Major Chords Sound Pleasant and Stable

• Harmonic Series: Major triads (like C–E–G) build directly from lower-integer frequency ratios (such as 4:5:6), which the human ear processes as clean, resonant, and restful.
• The Major Third: The distance from the root to the middle note is a major third (4 semitones), which sounds open and bright.
• No Need to Resolve: Because the intervals are simple and stable, major chords feel complete on their own. [1, 2, 3, 4, 5]

Discussion of Torricelli Ball-Drop

Demonstration:

Clock device, using Arduino Nano, DE3231 RTC, SSD1306 OLED, and Neopixel ring, as prototype for proposed sunset clock.