<aside> ☁️
side project you can absolutely build yourself even with zero experience
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🕰️ time
Few evenings if soldering is new to you One evening if it isn't
💸 cost
around 30 to 50$ for the electronics if you start from nothing (if you are brave you can get everything cheaper on Taobao/Temu 🙂)
<aside> 📹
The full tutorial video is coming to my YouTube next week…
You can watch me build the hairpin step by step (plus all the BTS). Click below to subscribe so you don’t miss it…
</aside>
A hairpin that records voice…
One press, one thought.
You record your voice, and it uploads the recording. A server stitches the audio, transcribes it, and structures it into aesthetic notes in your phone. (on Android it goes to Google Keep or Notion).
This is everything I used, everything I got wrong (so you don’t repeat my mistakes 😭) and every prompt I wrote.
<aside> 🫠
I found out there is an easier way to do all of this.
There is a version of the same board that already has the microphone and a memory card slot built in. So you don't need to solder this much, just the battery. If you choose that way it will be easier for sure
I found this out after I finished mine. So the guide below is written with both options.
</aside>
Option A, the one I actually built. Plain board, separate microphone on a wire. This is the exact setup my code and my numbers come from. You solder the mic and the battery, six connections total.
Option B, the easier one. XIAO ESP32-S3 Sense. The mic and microSD slot are already on the board, so you only solder the battery (2 joints). It can record for hours (instead of 2-3 min) and doesn’t need Wi‑Fi right away. It also comes with a camera you won’t use. Pop it off by lifting the connector tab with a fingernail, no soldering. That cuts the thickness from ~8–9mm to ~4–5mm, close to Option A, and leaves a flat connector on top.
| Option A (mine) | Option B (easier) | |
|---|---|---|
| Soldering | you’ll need to solder 3 parts: the Seed with Mic and battery, 6 joints | solder only one part - battery, 2 joints |
| Recording length | 2 to 3 min per note | Hours, until the battery dies |
| Needs WiFi | Right after recording | Later, whenever you get home |
| Thickness | About 3.5mm | 8 to 9mm with the camera, about 4 to 5mm once you pull it off |
| Total cost | 30 to 50 USD | 35 to 55 USD |
If you’ve never soldered and the idea scares you, take Option B. If you want to have fun soldering, take Option A.