# HP-01 — Assembly

Parts: `reservoir_body`, `lid`, `electronics_tower`, `tower_cover`, `grow_ring`,
`window_bezel`, `net_cup` (+ the electronics in the BOM). All screws are
self-tapping into the printed pilot bores.

## 1. Sight window (make the reservoir water-tight first)
The seal here is the **silicone bead + bezel clamp** — there is no thick gasket.
1. (Optional secondary seal) press a **Ø1 mm silicone O-ring cord** into the
   ~1.2 mm groove around the window rebate.
2. Lay the **clear PETG sheet** (46 × 118 × 2 mm) into the rebate on the
   reservoir's front (+Y) face.
3. Set the **window_bezel** over it and drive **4 × M3 × 12** into the four inner
   bosses. The bezel lip clamps the sheet into the rebate.
4. Run a thin bead of aquarium silicone around the sheet-to-rebate joint — **this
   is the real seal** — and cure 24 h.
5. **Leak-test** per PRINTING.md before going further.

## 2. Electronics tower (dry side)
1. **Feather ESP32-S3** → drop onto its four floor stand-offs, **4 × M2 × 8**
   from above. USB-C faces the back-wall cutout.
2. **MOSFET driver (5648)** → two stand-offs + the anti-rock pad, **2 × M2 × 8**.
3. Mount the **pH & EC Gravity boards** on the −X shelf (double-sided tape or the
   retaining lip).
4. **BH1750** → hang it under the **tower_cover** on its two stand-offs, chip up
   to the sky window, **2 × M2 × 8** from below.
5. **Seal the sky window:** drop the **clear Ø10 × 1.5 mm disc** into the rebate
   on the cover's TOP over the Ø6 light hole and fix it with a ring of clear
   silicone. It passes ambient light to the BH1750 but keeps spills and
   condensation out of the mains-powered box.
6. Wire everything per WIRING.md. The pH coax, EC coax and WS2812 3-wire leads
   drop from the lid's back cable slot, down the reservoir/tower gap, and into
   the tower through the **notch in the tower's front-wall top edge**. Then close
   the tower with the **tower_cover** (**4 × M3 × 12**).

## 3. Join the tower to the reservoir
Bolt the tower's front wall to the four Ø6 bosses on the reservoir's back (−Y)
face: **4 × M3 × 10** from inside the tower (reach in before/while wiring).

## 4. Probes
1. Fit a **Ø17 grommet** in each lid well (pH at +X, EC at −X).
2. Slide the **pH probe** down through the +X well until the BNC-cap shoulder
   rests on the catch rim. Its coax + BNC stay above the lid.
3. Slide the **EC probe** into the −X well the same way. Use a **LONG RIGID
   Ø16 BNC-class probe** (e.g. DFRobot K=1 / DFR0300-H) — NOT a short cabled
   TDS head, which would dangle and fall through the well.
4. Route both coax leads through the lid's back cable slot to the boards.

## 5. Grow ring
Adhere the **WS2812 tape** into the inward channel band of the **grow_ring**
(start at the back notch so the leads exit there). Press the ring onto the lid —
its four pegs snap into the lid holes. Route the LED leads through the back notch
+ lid slot to the MOSFET.

## 6. Plant it (Kratky method — no pump, ever)
1. Mix nutrient A+B into ~2.5 L of water per the nutrient label; fill the
   reservoir to the fill line (~135 mm — you can read it through the window).
2. Put the seedling in the **3-inch net cup** with clay pebbles / rockwool.
3. Drop the net cup into the lid centre hole — its lip catches. The cup base sits
   ~31 mm into the solution to start.
4. Set the lid on the reservoir (skirt laps the rim). Plug in USB-C.
5. **That's the whole method:** as the plant drinks, the level drops and the
   roots draw a growing **air gap** — no pump, no air stone. Top up with fresh
   nutrient when the window shows it low; leave the top few cm of root in air.

## Service
- **First unplug the two BNC connectors** above the lid (pH + EC). Then the
  **lid + net cup + probes + grow ring lift out as one unit** for topping up /
  cleaning.
- Tower cover (4 × M3) lifts off for the electronics (BH1750 rides with it).
- Reservoir scrubs out once the lid is off.
