# SaltyLab — Detailed Build Plan 🔬⚖️

Self-balancing two-wheeled indoor robot with AI brain.

---

## 1. Battery Analysis

### Pack Specs (Begode Master V1 packs)
- **Configuration per pack:** 10S (35V nominal, 42V full, 30V cutoff)
- **Chemistry:** Li-ion 18650 or 21700
- **Estimated capacity per pack:** ~450-500Wh (based on Master V1 total ~1800Wh ÷ 4 packs)
  - If 10S4P with 21700 5000mAh cells: 36V × 20Ah = **720Wh**
  - If 10S3P with 21700 5000mAh cells: 36V × 15Ah = **540Wh**
  - If 10S4P with 18650 3500mAh cells: 36V × 14Ah = **504Wh**
  - **Need to verify:** check cell count visible on pack, or weigh it

### SaltyLab Battery Config: Single Pack
- **Voltage:** 35V nominal (fits hoverboard ESC: designed for 36V/10S)
- **Capacity:** ~500Wh (conservative estimate)
- **Weight:** ~2-3kg per pack

### Why Single Pack is Enough
- SaltyLab is indoor-only, short missions
- One pack gives 2-4 hours runtime (see estimates below)
- Keep other 3 packs for SaltyRider and SaltyTank

---

## 2. Power Budget & Range Estimation

### Component Power Draw

| Component | Voltage | Current | Power (W) | Notes |
|-----------|---------|---------|-----------|-------|
| Jetson Nano | 5V | 2-4A | 10-20W | AI inference mode: ~15W avg |
| RealSense D435i | 5V (USB) | 0.7A | 3.5W | Depth + RGB streaming |
| RPLIDAR A1M8 | 5V | 0.5A | 2.5W | Spinning at 5.5Hz |
| BNO055 IMU | 3.3V | 0.01A | 0.04W | Negligible |
| ESC (idle/balance) | 36V | 0.3A | 10W | Maintaining balance, no movement |
| LEDs + misc | 12V | 0.5A | 6W | Status LEDs, speaker |
| DC-DC losses | — | — | ~5W | ~85% efficiency on converters |
| **Subtotal (idle/balancing)** | | | **~47W** | |

### Motor Power (Moving)

| Activity | Per Motor | Total (2 motors) | Notes |
|----------|-----------|-------------------|-------|
| Balancing in place | 5-15W | 10-30W | Continuous micro-corrections |
| Slow indoor movement (2 km/h) | 15-25W | 30-50W | Walking pace |
| Normal indoor (5 km/h) | 30-50W | 60-100W | Brisk walk |
| Fast / acceleration | 80-150W | 160-300W | Bursts, turning |
| Climbing threshold/ramp | 100-200W | 200-400W | Short duration |

### Total Power by Use Case

| Mode | Electronics | Motors | Total | Notes |
|------|-------------|--------|-------|-------|
| **Idle (balancing)** | 47W | 20W | **~67W** | Standing still |
| **Slow patrol** | 47W | 40W | **~87W** | Gentle movement |
| **Normal follow** | 47W | 80W | **~127W** | Following person around house |
| **Active (turning, accel)** | 47W | 200W | **~247W** | Bursts |

### Range Estimates (Single 500Wh Pack)

| Mode | Avg Power | Runtime | Distance |
|------|-----------|---------|----------|
| Idle (balancing) | 67W | **7.5 hours** | 0 km (stationary) |
| Slow patrol (2 km/h) | 87W | **5.7 hours** | ~11 km |
| Normal follow (5 km/h) | 127W | **3.9 hours** | ~20 km |
| Mixed indoor use | ~100W avg | **5 hours** | ~15 km |
| Aggressive (lots of turning) | 180W avg | **2.8 hours** | ~8 km |

**Bottom line: 3-5 hours of indoor use on a single pack.** More than enough.

### Weight Budget

| Component | Weight (g) | Notes |
|-----------|-----------|-------|
| Battery pack (1x) | 2500 | Estimated, weigh to verify |
| 2x 8" hub motors | 2400 | ~1200g each with tire |
| ESC board | 150 | Single board |
| Jetson Nano + heatsink | 280 | With Noctua fan |
| RealSense D435i | 72 | Very light |
| RPLIDAR A1M8 | 170 | With motor |
| BNO055 breakout | 5 | Tiny |
| DC-DC converters (2x) | 300 | 150g each |
| Frame + brackets | 1200 | Aluminum + 3D printed |
| Wiring + connectors | 200 | |
| Bumpers (TPU) | 150 | |
| **TOTAL** | **~7.4 kg** | Target: under 8 kg |

---

## 3. Detailed 2D Schematics

### 3.1 Base Plate — Top View

```
                         350mm
    ←─────────────────────────────────────→
    
    ┌─────────────────────────────────────┐  ─┬─
    │ ○                               ○   │   │
    │   ┌───────────────────────────┐     │   │
    │   │      MOTOR MOUNT PLATE    │     │   │
    │   │                           │     │   │
    │   │  ┌─────┐       ┌─────┐   │     │   │
    │   │  │AXLE │       │AXLE │   │     │   │  200mm
    │   │  │ L   │       │ R   │   │     │   │
    │   │  └─────┘       └─────┘   │     │   │
    │   │     ↑   250mm    ↑       │     │   │
    │   │     └─────────────┘      │     │   │
    │   │        track width       │     │   │
    │   └───────────────────────────┘     │   │
    │ ○                               ○   │   │
    └─────────────────────────────────────┘  ─┴─

    ○ = M5 mounting holes for vertical spine (4 corners)
    
    Axle holes: Ø14mm (standard hoverboard axle)
    Plate thickness: 6mm PETG
    
    Motor mount detail:
    ┌──────────────┐
    │  ┌────────┐  │
    │  │ Ø14mm  │  │   Two-piece clamp:
    │  │  axle  │  │   Bottom: part of base plate
    │  │  hole  │  │   Top: clamp plate with 2x M6 bolts
    │  └────────┘  │
    │  ○        ○  │   ○ = M6 clamp bolt holes
    └──────────────┘
         80mm
```

### 3.2 Side View — Full Assembly

```
                    FRONT →
    
    550mm ┬  ┌─────────┐
          │  │ RPLIDAR │ Ø80mm, 360° clear
          │  │  A1M8   │
    500mm │  ├─────────┤
          │  │         │ ← LIDAR standoff tube (80mm tall)
          │  │         │
    420mm │  ├─────────┤
          │  │RealSense│ ← Tilted down 10°, front-facing
          │  │ D435i   │   Adjustable bracket
    380mm │  ├─────────┤
          │  │         │
          │  │ JETSON  │ ← Noctua fan, ventilation slots
          │  │  NANO   │
    300mm │  ├─────────┤
          │  │ BNO055  │ ← IMU, vibration-isolated mount
    280mm │  ├─────────┤
          │  │         │
          │  │ ESC +   │ ← ESC board + DC-DC converters
          │  │ DC-DCs  │
    200mm │  ├─────────┤
          │  │         │
          │  │ BATTERY │ ← Heaviest component, lowest position
          │  │  PACK   │   Strapped to spine with velcro
          │  │         │
     80mm │  ├─────────┤
          │  │  BASE   │ ← Motor mount plate (6mm)
          │  │  PLATE  │
     40mm │  ├────┬────┤
          │  │    │    │
          ┴  └────┘    └── 8" wheel (Ø203mm)
             ═════════════
              GROUND (0mm)
    
    Ground clearance: ~40mm (bottom of plate to ground)
    Wheel contact to axle center: ~100mm (8" diameter / 2)
    Axle height from ground: ~100mm
```

### 3.3 Front View

```
              ←── 350mm ──→
              
              ┌─────────┐          ─┬─ 550mm
              │ RPLIDAR │           │
              ├─────────┤           │
              │   ┃     │  ← spine  │
              │   ┃     │  (2020    │
              │   ┃     │  extrusion│
              │   ┃     │  or       │
              │   ┃     │  aluminum │
              │   ┃     │  tube)    │
              │   ┃     │           │
              ├───┃─────┤           │
    ┌─────┐   │   ┃     │   ┌─────┐│
    │     │   │   ┃     │   │     ││  
    │ 8"  │   │   ┃     │   │ 8"  ││ 100mm
    │ L   │───┤   ┃     ├───│ R   ││ (axle)
    │     │   │   ┃     │   │     ││
    │     │   └───┃─────┘   │     │┴─ 0mm
    └─────┘       ┃         └─────┘
    ═══════════════════════════════════
    
    ←65→←──── 250mm ────→←65→
     mm    (track width)    mm
    
    Total width with tires: ~380mm
    Fits through standard doorway (760mm) ✓
```

### 3.4 Spine Detail — Side View

```
    ┌──┐ ← 20×20mm aluminum extrusion (2020 V-slot)
    │  │   or 25×25mm square aluminum tube
    │  │
    │  │──── Shelf bracket (3D printed, bolts to T-slot)
    │  │     Each shelf: 120mm wide × 100-150mm deep
    │  │
    │  │──── Shelf bracket
    │  │
    │  │──── Shelf bracket
    │  │
    │  │──── Shelf bracket
    │  │
    ├──┤
    │  │──── Base plate connection (L-brackets, 4x M5)
    └──┘

    Spine length: 470mm (from base plate to LIDAR mount)
    
    Shelf positions (from base plate):
      0mm  — Base plate
     30mm  — Battery shelf (holds pack on its side)
    150mm  — ESC + DC-DC shelf  
    250mm  — Jetson Nano shelf
    300mm  — BNO055 (attached to spine directly)
    370mm  — RealSense bracket (front-facing arm)
    420mm  — LIDAR standoff begins
    500mm  — LIDAR mount plate
```

### 3.5 Wiring Diagram

```
    BATTERY PACK (35V nominal, 10S Li-ion)
    ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
         │(+)                    (−)│
         │                          │
         ├──[E-STOP (NC)]───────────┤
         │                          │
    XT60 ├────────┬────────┬────────┤ XT60
         │        │        │        │
         │    ┌───┴───┐    │        │
         │    │DC-DC  │    │        │
         │    │36V→5V │    │        │
         │    │  4A   │    │        │
         │    └───┬───┘    │        │
         │     5V │        │        │
         │    ┌───┴────┐   │        │
         │    │USB Hub │   │        │
         │    │Jetson  │   │        │
         │    │RealSns │   │        │
         │    │RPLIDAR │   │        │
         │    └────────┘   │        │
         │                 │        │
         │    ┌────┴───┐   │        │
         │    │DC-DC   │   │        │
         │    │36V→12V │   │        │
         │    │  2A    │   │        │
         │    └───┬────┘   │        │
         │    12V │        │        │
         │    ┌───┴────┐   │        │
         │    │LEDs    │   │        │
         │    │Speaker │   │        │
         │    └────────┘   │        │
         │                 │        │
    ┌────┴─────────────────┴────────┴────┐
    │          HOVERBOARD ESC            │
    │          (FOC firmware)            │
    │                                    │
    │  I2C: SDA──BNO055──SCL            │
    │  UART: TX──Jetson──RX             │
    │                                    │
    │  PHASE L: ─── 8" LEFT MOTOR       │
    │  HALL  L: ─── (5 wire: hall A/B/C │
    │                + 5V + GND)         │
    │                                    │
    │  PHASE R: ─── 8" RIGHT MOTOR      │
    │  HALL  R: ─── (5 wire)            │
    └────────────────────────────────────┘
```

---

## 4. Phased Build Plan

### Phase 1: Rolling Skeleton (Days 1-3)
**Goal:** Prove balance works.

**Tasks:**
- [ ] Measure 8" motor axle diameter with calipers
- [ ] Design motor mount plate in CAD (FreeCAD or TinkerCAD)
- [ ] Print motor mount plate on Bambu X1C (PETG, 80% infill, ~4h print)
- [ ] Print axle clamp tops (x2)
- [ ] Mount both 8" motors to plate
- [ ] Mount ESC to plate with standoffs
- [ ] Wire BNO055 to ESC I2C (4 wires: VCC, GND, SDA, SCL)
- [ ] Wire battery to ESC (XT60)
- [ ] Modify FOC firmware: add BNO055 I2C read, replace gyro board input
- [ ] Flash ESC with updated firmware
- [ ] **SAFETY:** Tie rope from ceiling to plate as fall catch
- [ ] Power on, tune PID (start with Kp=20, Ki=0, Kd=0, increase gradually)
- [ ] Achieve stable free-standing balance (no rope)

**Parts needed:** motor mount plate, 2x clamp tops, M6 bolts, M3 standoffs
**Risk:** PID tuning can take hours of iteration. Be patient.

### Phase 2: Spine + Brain (Days 4-7)
**Goal:** Add Jetson, achieve remote-controlled movement while balancing.

**Tasks:**
- [ ] Cut aluminum extrusion/tube to 470mm for spine
- [ ] Print shelf brackets (4x) and L-brackets for base connection
- [ ] Assemble spine onto base plate
- [ ] Mount battery to lowest shelf (velcro straps)
- [ ] Mount ESC + DC-DC converters
- [ ] Mount Jetson Nano on shelf, connect 5V power
- [ ] Wire Jetson UART → ESC UART
- [ ] Install JetPack 4.6 on Jetson (if not already)
- [ ] Write serial bridge: Jetson Python → ESC UART commands
- [ ] Test: keyboard control (WASD) → speed/steer commands → balanced movement
- [ ] Tune speed response (acceleration limits, max speed for indoor)
- [ ] Add E-stop button (inline with battery positive)

**Software deliverable:** `saltylab_teleop.py` — keyboard-controlled balancing bot

### Phase 3: Eyes + Ears (Days 8-12)
**Goal:** See the world. Map a room. Detect people.

**Tasks:**
- [ ] Print RealSense bracket (adjustable tilt)
- [ ] Print LIDAR standoff tube + mount plate
- [ ] Mount RealSense D435i (front-facing, ~10° down tilt)
- [ ] Mount RPLIDAR A1M8 (top of spine, 360° clear)
- [ ] Install ROS2 on Jetson
- [ ] Install and test `realsense-ros` (verify depth stream)
- [ ] Install and test `rplidar_ros` (verify laser scan)
- [ ] Run `slam_toolbox` — drive around room, build 2D map
- [ ] Test person detection with SSD-MobileNet-v2 (TensorRT)
- [ ] Implement follow mode:
  - Detect person in RGB frame
  - Get distance from depth frame
  - PID to maintain 1.5m following distance
  - LIDAR for obstacle avoidance

**Software deliverable:** `saltylab_follow.py` — person-following balanced bot

### Phase 4: Polish + Personality (Days 13-17)
**Goal:** Make it feel alive. Make it SaltyLab.

**Tasks:**
- [ ] Print proper enclosures for all electronics
- [ ] Print TPU bumpers (front + rear)
- [ ] Print carry handle
- [ ] Add NeoPixel LED ring around LIDAR mount (status indication)
  - Blue breathing: idle/balancing
  - Green: following
  - Yellow: exploring/mapping
  - Red: error/low battery
- [ ] Add small speaker (USB or I2S to amp)
  - Boot sound
  - Acknowledge commands with beeps/chirps
  - Optional: TTS via Jetson ("I see you", "battery low")
- [ ] WiFi dashboard: live camera feed + map + battery status
- [ ] Battery voltage monitoring (ADC on ESC → Jetson via UART)
- [ ] Low battery return behavior (stop and beep)
- [ ] Integrate with Home Assistant (MQTT: location, battery, status)

### Phase 5: House Mapping + Autonomy (Days 18-24)
**Goal:** SaltyLab knows your house.

**Tasks:**
- [ ] Map every room (drive around manually, SLAM builds full floor plan)
- [ ] Save map, set up `nav2` for autonomous navigation
- [ ] Define waypoints: lab, living room, kitchen, hallway
- [ ] Patrol mode: visit waypoints on schedule
- [ ] Person detection + greeting ("hey Tee", "hi Inka")
- [ ] Integration with Bermuda BLE: know where people are, go to them
- [ ] Charging dock design (future: auto-dock when low)

---

## 5. Speed & Performance Specs

### Target Performance

| Parameter | Value | Notes |
|-----------|-------|-------|
| Max speed (indoor) | 5 km/h | Software limited for safety |
| Normal follow speed | 2-3 km/h | Walking pace |
| Turning radius | 0 (pivot) | Differential drive, spins in place |
| Ground clearance | 40mm | Clears door thresholds (~15mm) |
| Max incline | ~10° | Limited by motor torque + balance |
| Operating time | 3-5 hours | Single 500Wh pack |
| Charge time | ~2-3 hours | Using one of the existing chargers |
| Weight | ~7.5 kg | Easy to pick up with handle |
| Width | 380mm | Fits all doorways |
| Height | 550mm | Below table height |

### Motor Specs (8" hub motor, estimated)
| Parameter | Value |
|-----------|-------|
| Nominal voltage | 36V |
| Rated power | 250-350W per motor |
| No-load RPM | ~250 RPM |
| Wheel circumference | ~0.64m (Ø203mm) |
| Max wheel speed | 160 m/min = 9.6 km/h |
| Continuous torque | ~2-3 Nm |
| Stall torque | ~8-10 Nm |

---

## 6. Safety Considerations

| Hazard | Mitigation |
|--------|-----------|
| Falls over | TPU bumpers, max tilt cutoff (30°), low CoG |
| Runs away | Software speed limit (5 km/h), E-stop button |
| Pinches/crushes | No exposed gears, motor covers |
| Battery fire | BMS on pack, fused main power, no charging unattended |
| Hits furniture | LIDAR obstacle avoidance, bumper sensors (future) |
| Scares the cat | Slow acceleration, no sudden movements |

---

## 7. Shopping List (Items NOT in Inventory)

| Item | Price (CAD) | Source | Notes |
|------|------------|--------|-------|
| 2020 aluminum extrusion 500mm | ~$8 | Amazon/AliExpress | Spine |
| T-slot nuts + M5 bolts (pack) | ~$12 | Amazon | For shelf mounting |
| M6 bolts + nuts (axle clamps) | ~$5 | Hardware store | 4x sets |
| NeoPixel ring (24 LED) | ~$8 | Amazon | Status indication |
| Small speaker + amp (MAX98357A) | ~$10 | Amazon/Adafruit | I2S audio |
| E-stop mushroom button | ~$5 | Amazon | Safety |
| XT60 splitter/distribution | ~$8 | Amazon | Power wiring |
| Misc: heat shrink, zip ties, wire | ~$10 | — | Always need more |
| **TOTAL** | **~$66** | | Everything else: already owned |

---

*Last updated: 2026-02-27*
*Project: SaltyRover / SaltyLab*