# BYITL SP-01 — Smart Plant Pot

**Design pack, revision A (2026-07-22).** Every part in this pack is marked
`BYITL SP-01 revA g0.29.4 2026-07-22`, debossed on a hidden face.

A USB-C self-watering soil pot. A capacitive moisture probe and an ambient-light
sensor sit at the plant. An ESP32-S3 in a separate desk-side enclosure — with a
**1.02 L lift-out reservoir** — doses water through a 5 V micro peristaltic pump
when the soil reads dry.

**USB-C in, 5 V throughout. No battery, no BMS, no buck converter.** One wall
adapter runs the whole product.

---

## Why the electronics are not in the pot

Soil is wet, and a pot gets watered. Keeping the controller, pump and reservoir
in a separate desk-side unit means nothing electrical lives in the wet zone —
only the two sensors, which are sealed parts designed for it. Two slim runs
join the units, and they are deliberately kept apart: the I²C signal tether
climbs the pot's **+Y spine**, while the dose tube climbs the **−Y spine** on
the opposite side — fluid away from signal. Both are anchored with a cable tie
at each end so a tug on the desk lead never reaches a connector. Sleeve the two
together if you prefer a single lead running to the desk.

Inside the desk unit the same idea repeats: a full-height divider splits it into
a **wet bay** (reservoir) and a **dry bay** (boards + pump), so a reservoir
overflow has somewhere to go that is not the ESP32.

## What you get

| | |
|---|---|
| `stl/` | 7 printed parts, ready to slice |
| `step/` | the same parts as STEP, if you want to modify them |
| `renders/` | 6 studio views + 6 close-ups of each mount |
| `viewer.html` | open in a browser — spin the whole assembly, toggle parts |
| `assembly.glb` | the assembly for any 3D tool, real component geometry included |
| `bom.csv` | every purchased part, with a buy link |
| `WIRING.md` | the complete wiring, with the two parts people forget (C1, D1) |
| `PRINTING.md` | print settings and orientation per part |
| `ASSEMBLY.md` | build order |
| `ASSEMBLY-mates.md` | the machine-verified mate list, with exact coordinates |

The viewer and the GLB contain the **real vendor CAD** for the Feather, the
soil probe, the light sensor, the MOSFET driver and the pump — not stand-in
boxes. What you see is what you are building around.

## Overall size

| | |
|---|---|
| Pot (with spines) | 209 × 186 × 234 mm |
| Saucer | 210 × 210 × 15 mm |
| Desk enclosure | 234 × 110 × 108 mm |
| Reservoir | 1.02 L |

Every part fits a Bambu P1S (256³) without splitting.

## Electronics

| Ref | Part | Why |
|---|---|---|
| U1 | Adafruit Feather ESP32-S3 (5323) | Wi-Fi + BLE, and its USB-C port *is* the product's power inlet |
| U2 | Adafruit STEMMA Soil Sensor (4026) | Capacitive, not resistive — no exposed electrodes to corrode |
| U3 | BH1750 breakout | Ambient light, at the plant where it means something |
| U4 | Adafruit MOSFET Driver (5648) | Logic-level low-side switch; PWM-able so dose rate is adjustable |
| M1 | Micro peristaltic pump, 3–6 V | Fluid never touches the pump mechanism, only the tube |

Both sensors share one I²C bus, so the signal tether is a single 4-wire run —
it climbs the +Y spine, while the dose tube runs up the −Y spine on the far
side, kept clear of the wiring.

## Known limitation, stated honestly

The library CAD model for the pump has its two port barbs drawn 2.8 mm apart,
which is closer than two Ø5.1 barbs can physically be — so in the renders they
look like one port. The pump's overall size and every surface the mount grips
are correct and verified; only that internal spacing is unreliable. The
enclosure leaves over 20 mm of clear run in front of both ports, which
accommodates any real spacing, so this does not affect the fit. Identify which
barb your inlet tube is on before deciding the pump is running backwards.

## Before you print

Read `PRINTING.md` — the reservoir needs more walls than a default profile
gives it, and two parts have a preferred orientation.
