Pocket lightning detector

A while back, I was browsing websites with various components and modules when a lightning sensor cought my eye. I was really curious about how it works, so I started researching it. After watching a few Youtube videos about this module, I decided I had to try it out. Then I started thinking, and suddenly occurred to me that it would be really cool to create a small, portable, battery-powered device that fits in your pocket and detect lightnings. So why not? Why not just design my own PCB and build the entire device myself?

I really enjoyd this project because I tried out a lot of different thigs: studying datasheets and schematics, searching for and creating my own schematic, and designing the PCB and case.

Features

• The entire device is powered by a Li-Po rechargeable battery
• It uses the ESP-C3-MINI as the main microcontroller
• Has USB-C port for programming and charging the device
• AS3935 and MA5532-AE for lightning detection
• Detects lightning strikes up to 40 km away
• Records the distance, energy and current time of lightning strike
• Everything is stored in the internal RTC memory, which can store up to 50 lightnings strikes
• Communicates with a mobile via Bluetooth to synchronize the time and data
• Has audio feedback when a lightning strike been detected or other thing happened
• Various battery protections, such as overcharge, undercharge, over-discharge and overvoltage
• It uses deep sleep mode to get the longest possible battery life

CAD model

Everything is stored in a case consisting of two parts: a base and a top cover. The top cover is secured with four M3 screws and heat inserts, along with the PCB, which is secured with two screws. The buttons are labeled with icons for clear identification of their functions. The dimensions are 106 mm in length, 60 mm in width, and 35 mm in height.

Made in Fusion360

PCB

It includes two switches: one to turn on and of the device and other to activate Bluetooth. In the upper right corner, above the USB-C port, are chips for charging, protection, monitoring, and drawing power from the battery, there is also a connector for the battery. The lightning sensor communicates via I2C. The pull-up resistors are located under the ESP-32 near the edge of the PCB. The dimensions of PCB are 99.7 mm x 35 mm.

Schematic

PCB

Made in KiCad

⚠️ The area around the lightning sensor antenna must be kept sufficiently far away from metal parts, as there could interfere with the antenna. For this reason, there si no GND copper area around it, and no screws are located nerby.

Poster

Made in Figma

Firmware

It uses standard C++ code. One button turns the device on, and the other activates Bluetooth to display lightnings data and synchronize the time. The time must be synchronized every time the device is turned on. Data cen be currently displayed via a serial monitor application. Once the device is connected, it automatically sends lightning data every 3 seconds. Time is synchronized by sending a command, and the board then retrieves the current time. Lightning strikes and the time are stored in RTC memory, so they are erased when the device is turned off. The device runs continuously in deep sleep mode and wakes up only when a lightning strike occurs to save data about the strike and the time it happened, then goes back into deep sleep. RTC memory is the only component that remains active even when the device is in deep sleep mode. The RTC memory stores a maximum of the last 50 lightning strikes to prevent it from becoming overloaded. My goal was to maximize battery life, so I chose Bluetooth over Wi-Fi because Bluetooth is much more power-efficient, and I use deep sleep mode as well (Once the device is finished, I’ll carefully measure its battery life). You can found further details in the comments within the code. After i finished the device, I’ll probably create a nice app where the lightnings will be saved and can be viewed back in time.

BOM

You can find it in .csv format here.

License

This project is licensed under the GNU GPL v3.

Matyas604/Pocket-lightning-detector - Battery-powered Pocket Lightning Detector
Copyright (C) 2026 Matyáš Caha

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.

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Made with ❤️ by @Matyas604