Build the device

The Nightjar recorder is built from off-the-shelf parts and a printed case. No custom circuit board required. Here is what goes into one.

The parts

• An ESP32-S3 board with PSRAM. This is the brain: it has WiFi, Bluetooth and enough memory to buffer audio. A compact board with an onboard microphone and card slot keeps the whole thing tiny.
• A microphone. A digital I2S MEMS microphone for clean, low-noise audio.
• A microSD card. Where recordings are written. 16 to 32 GB is plenty.
• A small LiPo battery and a charging circuit, so it runs off the mains or on the go.
• A button and a status light for control and feedback.

A full bill of materials with exact parts and wiring ships with the project. Indicative cost is under thirty pounds, plus a printed case.

Step 1: Flash the firmware

The firmware is built with PlatformIO. Connect the board over USB and flash it.

cd nightjar/firmware
pio run -t upload
pio device monitor

The serial monitor confirms the board booted, found its microphone and card, and is ready to record.

Step 2: Print the case

The enclosure is a parametric model you can print in a couple of hours. Because it is parametric, you can re-tune it to the exact board and battery you chose, then print the two halves and snap them together around the electronics.

Step 3: Provision and record

Open the app, connect to the device over Bluetooth, and give it your WiFi details and your server address. Press the button to record. Put it on charge, and it uploads on its own. That is the whole loop.

Want the software side first? See self-host the server and connect your AI. Or skip the build entirely with a hosted plan.