Triad Spectrophotometer – Open-Source UV-Vis

A low-cost, portable, and open-source spectrophotometer for absorbance and transmittance measurements from 410 nm to 940 nm, based on the SparkFun AS7265x sensor and ESP32.

🔬 Scientific Background

Your project aligns with the growing trend of democratizing spectroscopy for environmental monitoring, education, and citizen science. As highlighted in recent literature:

• Portable spectrophotometers enable real-time water quality analysis (e.g., chlorophyll, nitrates, microplastics).
• The Beer-Lambert law forms the basis for quantitative analysis:
  ( A = \log_{10}(I_0/I) = \epsilon \cdot c \cdot l )
• Open-source designs reduce costs from thousands to under $100, while maintaining scientific validity.

This device is ideal for:

• Quantifying bioindicators (e.g., algae via chlorophyll absorbance)
• Detecting chemical pollutants
• Educational labs in chemistry and environmental science

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🧪 Features

• ✅ Dual-mode: Absorbance & Transmittance (%)
• ✅ 18-channel spectral range: 410–940 nm (UV-Vis-NIR)
• ✅ Hardware-synchronized LED control (external light source)
• ✅ Stable measurements: 5s LED warm-up + 10-reading average
• ✅ User-friendly GUI: Port selection, sample naming, real-time plotting
• ✅ Export-ready: CSV (with I₀, I, A, %T) and publication-quality PNG
• ✅ Cross-platform: Windows, Linux, macOS executables via GitHub Actions

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📦 Bill of Materials (BOM)

Component	Description	Photo	Where to Buy
ESP32 Dev Board	Microcontroller with Wi-Fi/Bluetooth, used for sensor control and serial communication.		Amazon
SparkFun Triad - AS7265x	18-channel spectral sensor (410–940 nm), with factory calibration in µW/cm².		SparkFun
External White LED	High-intensity light source for transmission measurements (connected to GPIO 32).		Amazon
Cuvette Holder	3D-printed or acrylic holder for standard 10 mm pathlength cuvettes.		Amazon

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🚀 Getting Started

Option 1: Download Executable (Recommended for users)

1. Go to Releases
2. Download the appropriate version:
   • spectrophotometer.exe → Windows
   • spectrophotometer → Linux
   • spectrophotometer.app → macOS
3. Install USB drivers if needed (CH340/CP210x)
4. Run the executable and follow the GUI instructions

Option 2: Run from Source (For developers)

git clone https://github.com/your-username/your-repo.git
cd your-repo
pip install -r requirements.txt
python spectrophotometer.py