# HP-01 — Wiring & Power

**USB-C only. No battery, no BMS, no buck converter.** One USB-C 5 V 2 A wall
adapter runs everything through the Feather's own 5 V (USB) pin.

```
USB-C wall adapter ─► Feather ESP32-S3 USB-C ─► Feather 5V (USB) pin
                                                  │
      ┌───────────────────────────────────────────┤
      ▼                                            ▼
  MOSFET Driver (5648)  V+ ◄── 5V           BH1750 (3V3, SDA, SCL, GND)
      │  low-side switch, gate ◄── Feather GPIO (LEDC/PWM)
      ▼
  WS2812 grow tape 5V rail  (DIN ◄── Feather GPIO via 330 Ω;  1000 µF across 5V)

  pH probe (BNC) ─► Gravity pH board ─► Feather ADC pin
  EC probe (BNC) ─► Gravity EC board ─► Feather ADC pin
```

## Connections

| From | To | Signal | Route |
|---|---|---|---|
| USB-C adapter | Feather USB-C | 5 V | Plug through the tower's back-wall cutout |
| Feather 5V | MOSFET V+ (screw term) | 5 V | Inside the tower |
| Feather GND | MOSFET GND | GND | Inside the tower |
| Feather GPIO (LEDC) | MOSFET signal (JST-PH) | PWM gate | Inside the tower |
| MOSFET switched out | WS2812 5V | 5 V | Tower → lid back slot → grow-ring notch |
| Feather GPIO | WS2812 DIN | DATA (330 Ω series) | Same run |
| Feather 3V3/SDA/SCL/GND | BH1750 | I²C (0x23) | Inside the tower (STEMMA QT → DuPont) |
| pH probe BNC | Gravity pH board → Feather ADC | analog | Well → lid → tower shelf |
| EC probe BNC | Gravity EC board → Feather ADC | analog | Well → lid → tower shelf |

## Every lead is reachable with the part installed

- **Feather USB-C** exits the tower's back wall through the modelled cutout (on
  the real receptacle centreline) — plug/unplug without opening anything.
- **MOSFET** screw terminals + JST face up; wire them with the tower cover off.
- **WS2812 tape** leads (5 V / GND / DIN) exit the grow-ring back notch, drop
  through the lid's back cable slot, and enter the tower through the notch in the
  tower's front-wall top edge.
- **All three signal runs** (pH coax, EC coax, WS2812 3-wire ribbon) drop from
  the lid's back cable slot, down the ~6 mm reservoir/tower gap, and into the
  tower through that same front-wall top notch — a straight, unpinched path.
- **BH1750** sits under the tower cover; its I²C leads are inside the tower. The
  cover lifts off (4 × M3) and the sensor rides with it.
- **pH & EC probes**: BNC head + coax sit ABOVE the lid, fully accessible for
  calibration/removal. Coax drops through the lid cable slot to the boards on the
  tower shelf.

## Firmware notes (not shipped here)

- WS2812 DIN on a spare GPIO; MOSFET gate on an **LEDC-capable** GPIO so the grow
  light can be PWM-dimmed and fully powered off overnight.
- pH/EC on two ADC pins; add a hardware RC filter or median-filter in firmware
  (the probes are high-impedance).
- BH1750 at I²C 0x23; add the pH/EC board addresses if using I²C variants.
- Add a series 330 Ω on the WS2812 data line and a 1000 µF cap across its 5 V
  rail (standard WS2812 practice).
