# RippleNode One Device Design

## Product Goal

**RippleNode One** is a very low-cost camera-free privacy node placed near a Wi-Fi router,
doorway, desk, cabinet, or protected zone. The device watches wireless signal changes and sends
local room-disturbance samples to the RippleGuard app.

This is not a medical device, body scanner, or safety-critical alarm.

## Cheapest First Device: RippleNode One

Build a USB-powered ESP32 module device.

```text
USB-C power
  -> 5V input protection
  -> 3.3V regulator
  -> ESP32-C3/S3/WROOM module as RippleNode One radio
  -> status LED
  -> calibration/reset button
  -> Wi-Fi RSSI firmware
```

Avoid battery in the first product. Battery adds charging safety, shipping complexity, thermal
testing, and support issues.

## Recommended Hardware Blocks

- Pre-certified ESP32 module, not bare chip
- USB-C power-only connector
- 5V to 3.3V regulator with enough current headroom
- ESD protection near USB-C
- One RGB or single-color status LED
- One tactile button for setup/calibration/reset
- Optional second button for factory reset
- Test pads for 3.3V, GND, EN, IO0, TX, RX
- Antenna keepout exactly as required by the module vendor

## Board Shape

Starter board:

```text
50 mm x 35 mm rectangular PCB
USB-C on one short edge
ESP32 module at opposite edge
Antenna facing outward with clear keepout
Button and LED on top face
Four mounting holes if using a case
```

Do not put copper, ground pour, battery, screws, or tall metal parts under or in front of the PCB
antenna area.

## Enclosure

Best first enclosure:

- Small puck or rounded rectangle
- USB-C port exposed
- One small LED window
- One recessed button
- Venting is usually unnecessary for USB-powered ESP32, but avoid sealing heat tightly
- Plastic only near the antenna

Prototype path:

1. Off-the-shelf plastic case
2. 3D printed case for pilot units
3. Injection molded case after the RF placement and user workflow are proven

## Placement Protocol

Best one-node placement:

- Near the Wi-Fi router
- Near a doorway
- Between router and protected area
- Near a desk/cabinet/bed edge

The signal becomes most useful when a person crosses the RF path between router and ESP32.

## Firmware Contract

RippleNode One should emit this local sample format:

```json
{
  "timestamp": 1720000000,
  "nodeId": "ripplenode-one",
  "rssi": -54,
  "motionEnergy": 42,
  "breathingProxy": 0.28,
  "confidence": 76
}
```

Future CSI firmware can keep the same app contract and add:

```json
{
  "amplitudeProxy": 0.42,
  "phaseProxy": 0.19,
  "subcarrierEnergy": 0.73
}
```

## Manufacturing Plan

1. Validate with ESP32 dev board and the current RippleGuard app.
2. Build 5-10 hand prototypes on a simple custom PCB.
3. Run placement trials in 3-5 rooms.
4. Tune firmware thresholds and app calibration.
5. Order 25-50 assembled pilot boards.
6. Use 3D printed or off-the-shelf enclosures.
7. Collect logs from real use cases.
8. Move to DFM review, compliance pre-scan, and 200-500 unit pilot.

## Approximate BOM

| Part | Notes |
| --- | --- |
| ESP32 module | Use a module with existing RF certifications |
| USB-C connector | Power-only is enough for simplest product |
| 3.3V regulator | Size for ESP32 Wi-Fi current spikes |
| ESD diode | Protect USB input |
| LED | Status and pairing feedback |
| Button | Setup/calibration |
| Passives | Pullups, caps, resistors |
| PCB | 2-layer can work if antenna layout is respected |
| Enclosure | Plastic; keep antenna side clear |

## Compliance Notes

Use a pre-certified radio module and follow its layout rules. Final product testing may still be
needed before commercial sale, especially if you change antenna layout, enclosure, power supply, or
sell in multiple regions. Treat this as an engineering checklist, not legal certification advice.

## Higher Accuracy Upgrade Path

- Two nodes: compare doorway/protected-zone changes
- Three or four nodes: stronger zone probability map
- ESP32 CSI firmware: richer signal features than RSSI
- mmWave add-on: better motion presence, higher cost

Start with RippleNode One because it is cheap and patent/product-friendly, then keep the app
protocol open for multi-node and CSI upgrades.