Skip to content

🔍 About the VL53L0X Sensor

PuffiMail uses the VL53L0X time-of-flight (ToF) sensor to measure distance inside your mailbox with high reliability. This sensor plays a key role in detecting whether new mail has been delivered.

🎯 Why We Chose VL53L0X

We selected VL53L0X after evaluating multiple options due to its:

  • ✅ Compact form factor, ideal for small enclosures
  • ✅ True distance measurement via time-of-flight, not reflectivity
  • ✅ Stable performance under various lighting and surface conditions
  • ✅ Low power consumption, perfect for battery-powered systems

📏 Sensor Specifications (Simplified)

Feature Value
Measurement Range 30 mm – 1000 mm
Practical Sensitivity ~2 mm change detection
Resolution 1 mm
Wavelength 940 nm (invisible laser)
Update Rate Up to 50 Hz

💡 PuffiMail is tuned to reliably detect distance changes of around 2 mm, which is sufficient to detect nearly all typical mail items — including envelopes, small packages, and folded letters.
⚠️ Exception: ultra-thin items such as postcards may not always trigger detection.

🧠 PuffiMail's Smart Measurement Algorithm

To improve detection reliability, PuffiMail uses a robust multi-step algorithm:

  • 📊 Multi-sampling: Takes 5 readings per measurement
  • ❌ Outlier rejection: Discards readings outside 30–1000 mm range
  • 📈 Median filtering: Uses median value to reduce noise
  • 📐 Baseline comparison: Compares current reading to saved empty-mailbox baseline
  • 📡 Status classification:
  • new_mail → current distance is noticeably shorter than baseline
  • empty → current within ±1 mm of baseline
  • unknown → invalid or missing data

This ensures reliable results even when dealing with dark, reflective, or uneven mail items.

⚠️ Installation & Maintenance Tips

  • Mount sensor firmly and facing downward
  • Avoid plastic tape or transparent covers in front of sensor
  • After installation, always click "Measure Distance" on the web interface to set a proper baseline

The VL53L0X, combined with PuffiMail's signal processing algorithm, enables a compact and intelligent mail detection system that just works.