Project · draft
BLE SOS Pendant with Loud Alarm (3D-Printed, XIAO ESP32-C3)
- intermediate
- 8-10 hours
A user-tested personal-safety alarm prototype responds to SDG target 5.2 on ending violence against women and girls in public and private spaces.
Safety notes
Read first. Prototype only. It does not replace India's 112 emergency service or the 112 India app, and it stores no location data.
- LiPo: use a cell with a protection circuit, check polarity before connecting to the XIAO BAT pads, never puncture, crush or short it, and stop using a swollen cell.
- Prototype only: it does not replace India's 112 emergency service or the 112 India app. Make that clear to anyone who tests it.
- The alarm is loud: test at arm's length, not next to your ear.
Draft and unofficial, not affiliated with Fab Academy or the United Nations. Check prices, GST and parts before you buy.
Summary
A long press sounds a loud alarm and sends a BLE alert to a paired phone page, which can show a pre-written message to share. Built with and tested by the people who will carry it; stores no location data.
What it teaches
Design a small 3D-printed enclosure with a recessed button that is hard to press by accident, drive a loud buzzer through a MOSFET, use BLE notifications to tell a paired phone (Web Bluetooth page), and charge a LiPo through the XIAO's battery pads while staying in low-power sleep.
Topics it touches, in Fab Academy-style terms:
- Computer-aided design
- 3D scanning and printing
- Electronics design
- Electronics production
- Output devices
- Networking and communications
Parts list
Parts cost
Some parts are not priced yet, so there's no total.
5 required parts are marked not priced yet below. Where a price is known it is shown per part, GST-inclusive as the seller listed it on 24 Oct 2026, with the GST rate unverified. Shipping is not included.
| Part | Qty | Unit | Price, GST-incl. as listed | Line cost | GST | Source |
|---|---|---|---|---|---|---|
| Seeed Studio XIAO ESP32C3 Wi-Fi & BLE Development Boardxiao-esp32c3 | 1 | pcs | ₹734 | ₹734 | GST unverified, typically 18% | Robocrazeread 24 Oct 2026 |
| LiPo cell 3.7 V ~500 mAh with protection circuit and JST leadlipo-3.7v-500mah-jst | 1 | pcs | not priced yet | not priced yet | GST unverified | no seller yet |
| Loud active piezo buzzer / alarm, 3-12 Vbuzzer-active-loud | 1 | pcs | not priced yet | not priced yet | GST unverified | no seller yet |
| N-channel MOSFET, SOT-23mosfet-nch-sot23Buzzer switch | 1 | pcs | not priced yet | not priced yet | GST unverified | no seller yet |
| 10 kOhm resistor, 1206 SMDres-10k-1206Gate pull-down | 1 | pcs | not priced yet | not priced yet | GST unverified | no seller yet |
| 100 ohm resistor, 1206 SMDres-100ohm-1206Gate resistor | 1 | pcs | not priced yet | not priced yet | GST unverified | no seller yet |
| 4-Pins DIP Momentary Square Tactile Push Button Switch 10 Pieces - 6x6x5mmbutton-tactile-6x6-x10Uses 1-2Pack: pack of 10 | 1 | set | ₹16 | ₹16 | GST unverified, typically 18% | Robocrazeread 24 Oct 2026 |
| 15cm x 10cm Single Side Copper Clad Laminate PCB Boardpcb-copper-clad-15x10Small milled carrier board | 1 | sheet | ₹39 | ₹39 | GST unverified, typically 18% | Robocrazeread 24 Oct 2026 |
| Part | Qty | Unit | Price, GST-incl. as listed | Line cost | GST | Source |
|---|---|---|---|---|---|---|
| Type C USB Cable (1 metre)cable-usb-c-1mSkip if you already have a data-capable USB-C cable | 1 | pcs | ₹65 | ₹65 | GST unverified, typically 18% | Robocrazeread 24 Oct 2026 |
| Premium 1.75MM HS PLA 1 KG 3d Printer Filament - Cement grey Colourfilament-pla-1kgPendant case; PETG/TPU also work; Fab Lab stock | 1 | pcs | ₹741 | ₹741 | GST unverified, typically 18% | Robocrazeread 24 Oct 2026 |
| Optional extras total, GST-inclusive as listed by the seller | ₹806 | |||||
The Part column links to the shared catalogue. Units are pcs, m, g, sheet or set, and a "set" is the seller's pack, as noted per part.
Tools you will need
- 3D printer
- PCB mill (small carrier board) or perfboard
- Soldering iron
- Phone with a Web Bluetooth browser (e.g. Chrome on Android)
Build notes
Step-by-step build notes have not been written yet for this draft. The summary, the topics above and the parts list are what exists so far.
How to buy
There is no online checkout. To buy or import these parts, email info@curiosta.com and say what you need. The button opens your own email app with a draft; nothing is sent until you send it.
Prices on this site are third-party seller listings, not a Curiosta quote. Ask by email for availability, price and GST.