NV-Center Optical Readout System — Fraunhofer IAO

Hardware and firmware platform for Nitrogen-Vacancy (NV) center-based optical sensing. Acquires photon-count signals from NV-center diamond samples, applies quenching pulses, and streams live data via a browser dashboard hosted on an ESP32-S3.

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System at a glance

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Module gallery

NV Module	Optical Module	Quenching PCB
		
Diamond sample holder	BPW34 photodetector	Rev-5 quenching board

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Hardware overview

Module	Description	Photo
NV Module	Diamond sample holder with optical coupling
Optical Module	BPW34 photodetector with signal conditioning
Quenching PCB (rev 5)	Laser/MW pulse driver for spin initialization
Readout Box	Enclosure integrating all modules
ESP32-S3	Main MCU — ADC readout + Wi-Fi web server
ADS1015 / ADS1115	External 12/16-bit ADC for precision readout

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Schematic

Full schematic PDF → SCH_Schematic4_2026-02-13.pdf

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Performance results

Metric	Value	Conditions
ADC noise floor	___ LSB RMS	ADS1115, PGA ±0.256 V
Sampling rate	___ Hz	Web server mode
Signal-to-noise ratio	___ dB	Laser power: ___ mW
Quenching pulse width	___ µs
Web dashboard latency	___ ms	LAN, single client

Figure 1 — Raw vs. optimized ADC readout (ADD CAPTION)

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Assembly walkthrough

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Web dashboard

Live ADC readout served from ESP32-S3 over Wi-Fi

After flashing, the ESP32 hosts a dashboard at the IP shown on the serial monitor:

• Live ADC signal plot
• Start / Stop acquisition
• CSV data export

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3D model

CAD files: Autodesk Inventor assemblies in Design/. Printable STLs in Design/Print/.

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Project structure

Fraunhofer/
├── Design/                        # Mechanical CAD (Autodesk Inventor)
│   ├── Parts/                     # Component libraries (PCB 3D models, connectors, sensors)
│   ├── Photos/                    # Renders and assembly photos
│   ├── Print/                     # 3D-printable STL exports
│   ├── Assembly_NV_Module.iam     # NV sensor module assembly
│   ├── Assembly_Optical_Module.iam
│   ├── Assembly_Quenching.iam
│   └── Assembly_Box.iam           # Enclosure assembly
│
├── Design Photos/                 # Step-by-step build photos and design plots
│
├── ESP32/                         # Firmware (PlatformIO / Arduino)
│   └── ReadOut/
│       ├── ESP32S3 ReadOut/                       # Base acquisition firmware
│       ├── ESP32S3 ReadOut Web Server/            # Web interface variant
│       ├── ESP32S3 ReadOut Web Server Optimized/  # Production variant
│       └── ESP32S3 Noise Optimization/            # ADC noise experiments
│
└── Ordered PCB/                   # Manufacturing files — PCB revision 5
    ├── Gerber_PCB5_2026-02-13.zip
    ├── BOM_Quenching_kit_PCB5_2026-02-13.xlsx
    ├── PickAndPlace_PCB5_2026-02-13.xlsx
    └── SCH_Schematic4_2026-02-13.pdf

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Firmware

Built with PlatformIO (Arduino framework).

cd "ESP32/ReadOut/ESP32S3 ReadOut Web Server Optimized"
pio run --target upload

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PCB manufacturing (rev 5)

File	Purpose
Gerber_PCB5_2026-02-13.zip	Upload to JLCPCB / PCBWay
BOM_Quenching_kit_PCB5_2026-02-13.xlsx	Bill of materials
PickAndPlace_PCB5_2026-02-13.xlsx	SMT assembly file
SCH_Schematic4_2026-02-13.pdf	Full schematic
3D_PCB5.step	3D PCB model

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Dependencies

Tool	Version
Autodesk Inventor	2024+
PlatformIO	Latest (VS Code extension)
EasyEDA	v6.5.51
ESP32 Arduino core	Latest stable

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Authors

Samuel Sanchez Moreno — Fraunhofer IAO (HiWi, 2025–2026)