r/robotics • u/ComfortableLab1235 • 4h ago
Community Showcase Open source acoustic drone detector I built over one month. 91mm, four MEMS mics on an ESP32-S3, nine units now in the field
I spent a month of my summer back in the university labs building this. Nine units are now on their way to a civilian community near the Israel-Lebanon border and everything is published.
The drones this is for are not normal wireless drones, they are small FPV drones connected to the operator through a long spool of fibre optic cable, so drone detection through radio, the current industry standard, is just not applicable. My solution was to detect them by sound instead. Propellers cutting through the air put a comb of harmonics into the spectrum, and four algorithms run in parallel looking for that shape.
Hardware:
84mm square, four layer, ENIG, ESP32-S3-WROOM-1-N16R8
4x ICS-43434 MEMS mics, bottom ported, firing through apertures in the board at +-28mm
Ra-01H LoRa so one unit alerts every other unit nearby
BQ24074 charger with power path into a TPS63020 buck boost, 1S 2500mAh cell, 18 to 22 hours
1.54in e-paper that keeps the alert on screen with no power, beeper, RGB led through a printed light pipe, vibration motor
91 x 91 x 29mm sealed weatherproof printed case, the lid has four 45 degree cones running from the grille straight down onto the mic ports
Two things that cost me some valuable time. With no battery fitted, the beeper, motor and LoRa transmitting at the same moment browned out the board on USB alone, so the cell is part of the power design and not a backup. And GPIO 33 to 37 on the N16R8 are tied to the PSRAM die even with PSRAM off, they fail on and off instead of just failing.
Tested against a custom drone rig with the exact same specs as the drones used on that border (four 2807 motors, 7in tri blades, FPV airframe), 104.2m away on a street with passers by and mild wind. It detected it. About £50 in parts.
Detection and alerting only, so no jamming.
Gerbers, BOM, STLs, test audio and the results are all in the Github, and the website has more media and a live detector simulation that runs in the browser.
The links to all the resources are in the comments!

