Wattplot v2 — Wiring Diagram

STALE — written for the v1 PCB (ESP32-WROOM-32E, BMI160, limit switches, GPIO4 DS18B20, GPIO16/17/18 DRV8871, GPIO19 grow-light relay, GPIO32 soil, GPIO33 battery, GPIO34/35 limits). The current hardware is ESP32-S3, schematic rev B (2026-08-03), with the pin map and BOM significantly changed. Use this as design intent (the harness topology, fusing, and outdoor-wiring practices are still valid) and cross-check every pin against:

• Pin map: docs/pinmap.html
• Schematic: docs/schematic.html (rev B, 2026-08-03)
• Firmware config: firmware/wattplot.yaml
• Firmware quick-start: firmware/README.md

A future pass will regenerate this doc against the current schematic. Tracked in ROADMAP.md.

Pin-by-pin wiring from the Wattplot Controller v1 PCB (in its waterproof enclosure, mounted on the bed’s east short wall) to every component on the apparatus. The PCB pin map is in docs/pcb_design.md.

Wire types: All low-voltage signal wires are 22-26 AWG stranded (silicone-jacketed for outdoor use, e.g., EcoWire). The 12 V battery and grow light cables are 16-14 AWG (use silicone wire for flexibility, e.g., 14 AWG silicone from a hoverboard battery supply). Solar panel leads are MC4 (the panel ships with them); the Sunapex ships with SAE connectors on both sides plus a polarity reversal adapter, so the panel MC4 connects directly to the Sunapex’s SAE adapter on the PV input. No MC4-to-bare-wire pigtail needed.

Cable lengths are the runs from PCB to component, with ~6” of slack at each end for service. JST-XH connectors at the PCB side; bare wire or ring terminals at the component side.

Charge controller: the Sunapex 10A MPPT (mini build) is a standalone waterproof charge controller — it has no host connection, runs its own MPPT, and handles bulk/absorption/float for LiFePO4. The ESP32 only reads battery voltage via the on-PCB 10 kΩ / 10 kΩ divider on GPIO 33; the controller’s own battery sense is what actually gates charging. The full-size v2 build (620 W panel) needs a larger MPPT sized to that panel — see docs/build_guide.md §7.

1. PCB header → component map

Power (12 V battery)

USB-C programming

I2C bus (BMI160 IMU, INA219, expansion)

The IMU is mounted on the panel frame (to measure actual tilt). The INA219 is on the motor lead (to measure actuator current). Both sit on the same I2C bus; daisy-chain with 4-wire cable.

UART (DPS5005 MPPT controller)

Removed in v2.4 — replaced by the Sunapex 10A MPPT standalone MPPT (see “Solar charge controller” below). The Sunapex has no host connection; ESP32 only reads battery voltage through the divider. The PCB’s J4 footprint and GPIO 26 / 27 pads remain on the board but are unpopulated (DNP) on the mini build — they are reserved for the full-size v2’s larger MPPT (RS-485 or VE.Direct).

On the full-size v2 build, this section returns with whatever UART/ RS-485 the chosen MPPT uses (e.g., Victron VE.Direct on UART2 for telemetry, or EPEver RS-485 Modbus). The pin map stays the same (GPIO 26/27, J4 footprint).

Solar charge controller (Sunapex 10A MPPT, mini only)

The Sunapex has no host connection. It sits on the bed wall, has its own internal MPPT, bulk/absorption/float for LiFePO4, and all charging protections. The PCB does not talk to it.

The Sunapex is powered by the battery, not the panel — connect the battery first, then the panel. Reverse-polarity on either side is protected (the Sunapex just won’t start).

Mode button: press until the LCD shows the LiFePO4 chemistry mode (usually labelled “Li” or “LiFePO4”, depending on firmware rev). Default out-of-box is sometimes sealed lead-acid — verify this on first power-up.

No telemetry back to ESPHome. The Sunapex has no UART / Bluetooth / Modbus output (the “Bluetooth” claim on some Amazon listings is for the family of products; the 10A SKU has only the LCD + LEDs). If you later want charge telemetry, swap to a Victron SmartSolar 75/10 (~$100, has VE.Direct UART + Bluetooth) — the wiring doc’s “UART (DPS5005 MPPT controller)” section above is the re-instantiation point.

Grow light relay (12 V switched output)

Grow light is 12 V LED strip or 12 V COB panel, ~20 W. The relay (K1) is rated 10 A at 125 VAC / 10 A at 30 VDC, plenty of headroom for a 20 W LED.

Linear actuator

The actuator is on the north rail of the frame. The cable runs through a flexible cable carrier or just a drip loop to allow tilt motion.

Limit switches (hinge end-stops)

The 0° switch is mounted on the bed’s south wall, just below the hinge axis. It triggers when the frame is fully flat. The 90° switch is on the north rail of the frame, triggering when the frame reaches vertical. Both are NO (normally open) roller switches with a 10 kΩ pullup at the PCB (not at the switch — long wire runs benefit from PCB-side pullup to avoid noise pickup).

DS18B20 soil temperature

Mounted 6” deep in the bed soil, near the center.

Soil moisture sensor (capacitive)

Capacitive sensor mounted in the bed soil, near the DS18B20. Powered from the same 3V3 rail as the DS18B20 (use a tap on the J8 3V3 wire, not a separate connection, to avoid voltage drop).

Battery voltage sense (divided)

The 12V → divided voltage is done on the PCB (R1 = 10kΩ from 12V to TP4, R2 = 10kΩ from TP4 to GND). J10 just brings the divided signal (GPIO33 input) and GND back to the connector. So J10 is a 2-wire cable from PCB to itself — actually, J10 is a connector on the PCB, with a jumper or short wire from J1’s 12V to the divider input. In practice you can omit J10 entirely and use the 10k divider as a through-hole component on the PCB, with the divider input tapped from the 12V rail right at the fuse output.

Simplification: skip J10 entirely. Solder the two 10 kΩ resistors on the PCB, with one end to 12V (after F1) and the other end to GND. The middle tap goes to GPIO33. The wiring on the schematic stays as J10 for documentation, but the actual PCB can have the divider as a small 2-resistor network on the board.

2. Total wire run summary

Total wire: ~75 ft of 26 AWG + ~22 ft of 14 AWG + ~4 ft of 12 AWG.

JST-XH connectors: ~12 connectors (3-4 pin each), $2-3 total.

3. Cable routing diagram

Top-down view of the bed + frame:

       ┌────────────────────────────────────────────────────┐
       │                  96" bed length                     │
       │                                                    │
       │  [PCB]                                    [IMU]    │
       │  enclosure    [limit sw 0°]                       │
       │  on east      at south wall                       │
       │  wall         ↓                                    │
       │  │            ╓─╳─╖ ←─── hinges (4) ─────          │
       │  │            ║   ║                                │
       │  │            ║ F ║   FRAME (96"×44.6" rectangle) │
       │  │            ║ R ║   2x6 PT perimeter             │
       │  │            ║ A ║   + 2x4 diagonal brace          │
       │  │            ║ M ║                                │
       │  │            ║ E ║   ▓ panel (97"×44.6")          │
       │  │            ║   ║                                │
       │  │            ╙───╜   ┌─────────────┐              │
       │  │                    │ limit sw 90°│              │
       │  │                    └─────────────┘              │
       │  │                                                   │
       │  └────[cable carrier]────[actuator]────             │
       │         on north rail    [battery 12V]             │
       └────────────────────────────────────────────────────┘

       Legend:
         [PCB]  = Wattplot Controller v1 PCB (in enclosure)
         [IMU]  = BMI160 IMU on the frame
         [actuator] = linear actuator on north rail
         [limit sw 0°] = roller switch on south wall (triggers at flat)
         [limit sw 90°] = roller switch on frame (triggers at vertical)
         [battery 12V] = 12V LiFePO4 (e.g., 100Ah) under the bed

Key routing rules:

1. Power first: 12 AWG from battery to PCB. Fused within 6” of battery (+).
2. Motor cable: 14 AWG from PCB to actuator. Through a flexible cable carrier (or a simple drip loop with 4” of slack) to allow tilt motion.
3. IMU cable: 26 AWG 4-wire from PCB to IMU on the frame. Through the cable carrier with the motor cable. Twisted pair to reduce noise.
4. Soil sensor cables: 26 AWG 3-wire (DS18B20) and 2-wire (soil moisture), routed through a grommet in the bed’s south wall into the soil. Both sensors buried 6” deep, 12” from the south wall.
5. Limit switches: 26 AWG 3-wire from PCB to the hinge area. The 0° switch mounts on the south wall just below the hinge axis. The 90° switch mounts on the north rail of the frame.
6. Sunapex MPPT + grow light: Sunapex mounts on the bed’s east wall (next to the PCB enclosure) — IP67, so it can be exposed. 14 AWG from grow light back through the south wall grommet; 14 AWG from Sunapex BAT+ through a 3 A in-line fuse to the battery.

4. Connector pinouts (JST-XH, all viewed from the wire side)

J1 — Battery (XT60):

Pin 1: V+ (12V)
Pin 2: V− (GND)

J2 — I2C breakout:

Pin 1: 3V3 (red)
Pin 2: GND  (black)
Pin 3: SDA  (white)
Pin 4: SCL  (green)

J4 — DPS5005 UART (RESERVED, DNP on v2.4 mini):

Pin 1: 3V3 (red)
Pin 2: GND  (black)
Pin 3: TX  (white) → ESP32 sends to DPS5005 RX
Pin 4: RX  (green) ← ESP32 receives from DPS5005 TX

Not populated on the v2.4 mini build. Will be re-instantiated on the full-size v2 build for a Victron VE.Direct or EPEver RS-485 connection to that build’s larger MPPT.

J5 — Grow light:

Pin 1: 12V switched (red) → to grow light (+)
Pin 2: 12V battery   (red) → from J1 (looped)

(Wait, this has only 2 pins, not 3. Let me re-check the PCB spec.)

J5 — Grow light (revised, 2-pin):

Pin 1: 12V switched (relay K1.NO → K1.COM)
Pin 2: 12V battery in (looped from J1)

The grow light has 2 wires: 12V switched, and GND (which comes from the common ground rail). So the grow light gets:

• 12V switched (from J5 pin 1) — from the relay
• GND (from common ground, e.g., the battery − terminal)

This means the grow light cable has only ONE 14 AWG wire for 12V, and the ground return is through the common ground (separate wire or via the chassis/battery negative). The JST-XH connector is 2-pin for the 12V side; the ground return is via a separate 14 AWG wire from the battery to the grow light.

Hmm, that means a 3-pin connector is cleaner. Let me update the PCB:

J5 — Grow light (3-pin):

Pin 1: 12V battery in (looped from J1)
Pin 2: 12V switched out (to grow light)
Pin 3: GND (to grow light ground)

The grow light has 2 wires going to the PCB: switched 12V and GND. The PCB has the battery 12V looped to J5 to power the relay.

OK let me finalize the wiring list. The grow light cable is 2 wires (12V switched, GND) plus 1 wire for the battery loop (12V in). That’s 3 wires total to/from the grow light area.

5. Final cable list (with wire colors)

6. Tools for wiring

• Wire stripper (22-12 AWG range)
• JST-XH crimper (PA-09 or equivalent)
• XT60 connector crimper
• MC4 crimper (iCrimp IWS-2546M, ~$25) — for the panel MC4 pigtails if you’re making your own. Skip if you buy pre-made MC4 extension cables with bare leads (Amazon, ~$6/pair).
• MC4 unlock tool (the little plastic spanner, ~$2)
• Multimeter (for continuity, voltage checks)
• Heat-shrink tubing (3 mm and 6 mm)
• Cable ties + cable carrier (for the actuator/IMU cable to the frame)
• Grommets (for the bed wall penetrations — 4× grommets for the sensor cables + 1× for the battery cables + 1× for the actuator cable)
• Silicone sealant (for sealing grommets against rain ingress)

7. Wiring checklist (pre-power)

Before connecting the battery, verify:

• All JST-XH connectors are fully seated (audible click)
• No bare wire is exposed at any connector
• Battery fuse (F1) is NOT installed yet (install last)
• All sensor cables are routed through grommets and sealed
• Cable carrier is installed on the frame-to-bed cable run
• MC4 polarity: red → Sunapex PV+, black → Sunapex PV−
• Sunapex BAT+ / BAT− polarity: red to battery +, black to battery −
• Sunapex battery-mode button: pressed to LiFePO4 setting (LCD shows “Li” or “LiFePO4”)
• Multimeter continuity check: no shorts between 12V and GND
• Multimeter continuity check: no shorts between 3V3 and GND
• Multimeter continuity check: each limit switch closes when pressed (should be 0 Ω or close)

When all checks pass: install the fuse. Connect the battery to the Sunapex first (it powers up the Sunapex’s MCU). Then connect the panel MC4 to the Sunapex PV input. Power on. Verify the ESPHome boot sequence in the serial monitor.