Lightning Detector Unit

Detects lightning, sounds the alarm, and tells everyone nearby when it’s safe to return. Cheap and no internet required.

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Inspiration

Many small beaches, youth sports fields, and campus events still clear people out only after someone hears thunder. Professional lightning warning systems exist but are expensive, so I built a low-cost station that detects lightning and warns everyone nearby automatically.

What it does

  • Detects lightning and estimates the storm's distance (1–40 km).
  • Rejects false alarms: man-made electrical noise is logged as a "disturber" but never triggers the alarm.
  • Warns people on site with a flashing LED and buzzer siren when a strike is within a set distance.
  • Alerts phones without internet: the station hosts its own Wi-Fi and dashboard; open phones get a full-screen warning, sound, and vibration.
  • All-clear countdown: each strike restarts it (15 s for the demo; the real rule is 30 minutes).
  • Simulation mode: a handheld wand triggers clearly labeled simulated strikes, with distance estimated from its radio signal strength.

How I built it

  • Hardware: ESP32, AS3935 lightning sensor, LED, and passive buzzer in a 3D-printed enclosure.
  • Sensing: lightning emits radio bursts. The sensor's LC antenna resonates near 500 kHz, at f=1/(2*pi*sqrt(LC)). My calibration routine tests all 16 tuning-capacitor settings and picks the one closest to 500 kHz.
  • Firmware: the ESP32 reads sensor events over SPI, runs the alarm and countdown, and serves the dashboard from its own access point. The wand is a second ESP32 communicating over ESP-NOW.

Challenges I ran into

  • Power: an audio amplifier drew enough current to crash the ESP32, so I switched to a directly driven buzzer.
  • A failed INT connection: the firmware now polls the sensor over SPI instead.
  • Indoor electrical noise from chargers, laptops, and Wi-Fi, which led to mounting the sensor on a mast.

Accomplishments I'm proud of

  • A working system: detection, alarm, offline phone alerts, and an all-clear countdown.
  • A real-time dashboard served entirely from a microcontroller.

What I learned

  • How lightning detectors tell lightning apart from man-made noise
  • Soldering and microcontroller basics

What's next

  • Testing device on actual storms
  • Storm direction with a second antenna
  • Solar power and a weatherproof enclosure
  • A network of stations across a beach or campus

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