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.