# Mobile Home Robot — Bill of Materials (concept spec)

Two variants share the base + lift; they differ in the top (articulated arm vs compact gantry).
mobile_base.urdf = base + lift + 4-DOF arm. mobile_gantry.urdf = base + lift + compact XYZ gantry.

## Base (differential drive)
| Item | Qty | Spec |
|---|---|---|
| Chassis plate / 2020 frame | 1 | ~400×300 mm |
| Driven wheel | 2 | ~120 mm, rubber |
| Drive motor | 2 | geared DC + encoder, or NEMA23 (torque for a loaded base) |
| Motor driver | 1 | dual H-bridge (or stepper drivers) |
| Caster | 2 | swivel, front/back |
| IMU + wheel encoders | 1 set | odometry |

## Vertical lift (reuses the gantry lesson)
| Item | Qty | Spec |
|---|---|---|
| 2040 mast | 1 | ~850 mm |
| **T8 leadscrew + nut** | 1 | **self-locking → arm holds on power-off** (same as gantry Y) |
| NEMA17 | 1 | lift drive |
| MGN12 rail + block | 1 | ~600 mm, lift guide |
| Lift carriage plate | 1 | printed (adapt carriage_plate.stl) |

## Manipulator
- Arm variant: 4× STS3215 (reuse) + printed holders/brackets.
- Gantry variant: 3× NEMA17 + MGN12 + GT2/T8 (see docs/gantry/BILL_OF_MATERIALS.md, scaled down).

## Compute + sensing + power
| Item | Qty | Spec |
|---|---|---|
| SBC | 1 | Raspberry Pi 5 / Jetson Orin Nano (nav + control) |
| Base lidar or depth cam | 1 | SLAM / obstacle avoidance |
| Wrist camera | 1 | Arducam B0332 (docs/camera_mount) |
| Battery + BMS | 1 | 24 V Li-ion, ~10 Ah |
| Buck converters | 2 | 24→12 V (servo bus), 24→5 V (SBC) |

## Rough budget
Base+drive ~$120, lift ~$80, compute+sensing ~$250, battery ~$80, plus the manipulator (arm ~$0 reuse, or
gantry ~$200). **≈ $500–700** depending on variant. A real multi-week build — this is the LATER horizon.