WebShooter

🕸️ WebShooter — Wearable Actuation & High-Response Sensing PCB

1. 🎯 Objective

WebShooter is a compact, high-reliability wearable controller PCB designed for rapid biosignal/force acquisition, low-latency electronic valve actuation, and external brushless motor ESC control.

Built around the ESP32-C3 SuperMini (RISC-V 32-bit architecture), the system is engineered to withstand intense inductive transients and severe electromagnetic interference (EMI) from high-power loads while providing precision analog readings from a Force Sensing Resistor (FSR).

[!NOTE] Key Capabilities:

• Fast Response Time: Sub-millisecond analog force detection via hardware RC filtering.
• Inductive Load Immunity: High-speed Schottky flyback suppression and isolated ground return loops.
• Modular Design: Socketed MCU mounting for effortless replacement and maintenance.

2. 🏗️ System Architecture

graph LR
    subgraph Power_Stage ["Power and Regulation Stage"]
        BATT["Battery LiPo 2S (7.4V - 8.4V)"] -->|J_BATT| LDO["AMS1117-3.3 LDO"]
        LDO -->|"10uF In + 22uF Out"| V33["3.3V DC Clean Rail"]
    end

    subgraph MCU_Stage ["Control Unit ESP32-C3 SuperMini"]
        V33 --> MCU["ESP32-C3 (RISC-V @ 160MHz)"]
        MCU -->|GPIO8| LED["Status Indicator LED"]
    end

    subgraph Sensor_Stage ["Analog Force Sensing"]
        V33 --> FSR_DIV["10k Ohm Reference Divider"]
        FSR["FSR402 Sensor"] --> FSR_DIV
        FSR_DIV -->|"100nF LowPass + 1k Ohm Prot"| ADC["GPIO0 (ADC1_CH0)"]
    end

    subgraph Actuation_Stage ["Power Actuation and Motor Drive"]
        MCU -->|GPIO7 Logic Gate| DRV["AO3400A N-MOSFET (30V / 5.7A)"]
        BATT -->|7.4V Heavy Rail| SOL["Solenoid Valve (Inductive Load)"]
        DRV -->|"Drain + SS14 Flyback Diode"| SOL
        MCU -->|"GPIO6 PWM - 100 Ohm Damper"| ESC["External ESC (SpeedX2 1404 BLDC)"]
        BATT -.->|"Direct Battery Wiring"| ESC
    end

• MCU: ESP32-C3 SuperMini (RISC-V 32-bit single-core @ 160 MHz, 400 KB SRAM, 4 MB Flash, Wi-Fi + BLE 5).
• Analog Front-End (AFE): Precision voltage divider with a 100 nF ceramic low-pass filter ($f_c \approx 159\text{ Hz}$) and $1\text{ k}\Omega$ series current limiter.
• Power Management & Drive: AMS1117-3.3 LDO regulator with dual ceramic filtering; logic-level AO3400A N-MOSFET with SS14 Schottky flyback protection; isolated ESC PWM signaling.

3. 🔬 Component Selection & Design Decisions

4. 📐 Schematic Overview

Full vector PDF schematic is available in the /schematic folder.

[!TIP] Complete Schematic Documentation:

• 📄 PDF Format: schematic/WebShooter_Schematic.pdf
• 🎨 Vector SVG: schematic/WebShooter_Schematic.svg/
• 💻 KiCad Source: pcb/WebShooter.kicad_sch

5. 🖨️ PCB Layout & Routing Strategy

Top Layer 2D Layout (F.Cu)	Bottom Layer 2D Layout (B.Cu)

3D Render - Top Side	3D Render - Bottom Side

🛠️ Layer Stackup & Dimensions

• Layer Count: 2-Layer FR4 ($1.6\text{ mm}$ board thickness, $1\text{ oz} / 35,\mu\text{m}$ copper weight).
• Board Dimensions: $38.0\text{ mm} \times 38.0\text{ mm}$ with $2.0\text{ mm}$ corner radius fillets (Ultra-compact wearable standard).
• Mounting Hole Grid: 4x M2 mounting holes on a $31.0 \times 31.0\text{ mm}$ pattern ($3.5\text{ mm}$ from board edges).

📐 Routing Guidelines & DFM Standards Applied

1. Strict 45° Mitered Routing (Zero 90° Corners):
   • All track bends utilize 45-degree chamfers or smooth radii.
   • Why: Eliminates acid traps during chemical etching in fab, avoids acute impedance steps, and prevents solder mask delamination.
2. Edge Pullback Clearance ($\ge 1.0\text{ mm}$):
   • All copper tracks, vias, and copper pour zones maintain at least $1.0\text{ mm}$ of clearance from the Edge_Cuts perimeter.
   • Why: Prevents copper shearing, burrs, and shorts during CNC V-scoring and board routing.
3. Trace Width Dimensioning (IPC-2152):
   • Power & Solenoid Traces: $1.0\text{ mm} - 1.2\text{ mm}$ (Handles up to $3\text{A}$ continuous with $\Delta T < 10^\circ\text{C}$).
   • 3.3V Power Distribution: $0.8\text{ mm}$.
   • Digital PWM & Analog Signals: $0.35\text{ mm} - 0.40\text{ mm}$.
4. Dual Continuous Ground Planes:
   • Both F.Cu and B.Cu feature unbroken GND copper zones connected through thermal reliefs (ZONE_CONNECTION_THERMAL) on all through-hole and SMD ground pins.

6. ✅ DRC & Quality Verification

Automated Design Rule Check (DRC) executed via kicad-cli:

** KiCad 10 Design Rule Check Report **
Project: WebShooter.kicad_pcb
Date: 2026-08-20

[+] Status: PASSED
[+] Total DRC Violations: 0
[+] Unconnected Elements: 0
[+] Footprint Courtyard Overlaps: 0
[+] Solder Mask Bridges: 0
[+] Silk Over Exposure: 0

[!IMPORTANT] The full verification report is saved in pcb/WebShooter-drc.rpt.

7. 🧊 3D Model & Mechanical Integration

• PCB 3D Model: Ready-to-import STEP file:
  • 📁 3d-model/WebShooter.step
• Wearable Case / Enclosure (CAD): Parametric wrist case model for 3D printing:
  • 📦 3d-model/WEBSHOOTERCASEFINAL.f3d (Autodesk Fusion 360 source archive)
• Mechanical Mounting: 4x M2 mounting holes on a $31.0 \times 31.0\text{ mm}$ square grid ($3.5\text{ mm}$ edge offset), designed to mate directly with the 3D-printed enclosure standoffs.

8. 🏭 Manufacturing & Assembly (JLCPCB / PCBWay Ready)

🚀 Production Parameters Recommended

• Base Material: FR-4 (Tg 130–140°C).
• PCB Thickness: 1.6 mm.
• Copper Weight: 1 oz ($35,\mu\text{m}$).
• Surface Finish: HASL Lead-Free or ENIG (Electroless Nickel Immersion Gold).
• Solder Mask: Matte Black / Blue / Green.
• Silkscreen: High-contrast White.

📜 License

This project is licensed under the MIT License — Feel free to use, modify, and manufacture this board for open-source and commercial hardware projects.