S M A R T V E R T I C A L H Y D R O P O N I C S T O W E R Smart Vertical Tower · Schematic Rev 2 · 2026-05-11 ESP32 · 12V DC · Water Pump · LED Strips · DHT22 · TSL2591 · XKC-Y25-V · TC4427 Gate Driver 12V 5V GND 3.3V GPIO4 I2C SENSOR GPIO25 GPIO26 ── 12V BUS ── 12V PSU 15A DC Switching Supply 10A FUSE XL4015 BUCK 5V 12V → 5V Set to 5.15–5.20V GND 12V IN 5V OUT ── 5V RAIL ── ESP32 30-pin Module 3.3V internal LDO 3.3V INT RAIL 3.3V GPIO4 VIN GND GPIO34 (input only) SDA SCL GPIO25 GPIO26 DHT22 Temp / Humidity VCC=3.3V · GPIO4 3.3V ① VCC ④ GND GPIO4 ② DATA TSL2591 Light Sensor I2C · 0x29 3.3V VCC GND SDA/SCL SDA SCL XKC-Y25-V Water Level Non-contact · 5V 5V BRN VCC BLK OUT BLU GND DIVIDER R5 10kΩ · R6 20kΩ IN OUT GND C1 100nF TC4427 Dual Gate Driver 12V VDD · Non-inverting IN-B → OUT-B (PUMP) IN-A → OUT-A (LED) Vgs=12V · Rds=8.7mΩ ✓ IN-B IN-A OUT-B OUT-A VDD GND R1 22Ω Z1 15V R2 22Ω Z2 15V IRLB8721 #1 PUMP N-ch · TO-220 ✓ Vgs=12V — fully on + HS1 ★ G D S 1N 4007 K A PUMP 12V DC · ~1–2A Inductive · 1N4007 ∥ protection + 12V − IRLB8721 #2 LED N-ch · TO-220 ✓ Vgs=12V — fully on + HS2 ★ G D S LED STRIPS 4× 1.5m · Parallel · ~8A 12V · Each fed AWG18 × 30cm No flyback needed ✓ + 12V − ── COMMON GROUND BUS ── POWER BUDGET Component Rail Current LED Strips (4× parallel) 12V ~8A Water Pump 12V ~1–2A ESP32 + Sensors 5V→3.3V <0.5A TC4427 gate driver 12V <15mA Total (simultaneous) 12V ~9.5–10.5A PSU Rating (Rev 2) 12V 15A rated ✓ XKC-Y25-V VCC 5V (min) <50mA BILL OF MATERIALS · Rev 2 PSU — 12V 15A DC Switching △ UPGRADED F1 — 10A Fuse, inline positive rail U1 — XL4015 Buck △ set 5.15–5.20V U2 — ESP32 30-pin Module U3 — DHT22 (temp/humidity · GPIO4) U4 — TSL2591 (I2C light · GPIO21/22) U5 — XKC-Y25-V (water level · 5V) U6 — TC4427 Dual Gate Driver ★ NEW · LCSC Q1,Q2 — IRLB8721 TO-220 ×2 (pump + LED MOSFET) HS1,HS2 — TO-220 Clip-on Heatsink ×2 ★ NEW D1 — 1N4007 (pump flyback) C1 — 100nF MLCC (TC4427 VDD bypass, within 5mm) ★ NEW Z1,Z2 — 15V Zener ×2 (gate Vgs clamp) ★ NEW R1,R2 — 22Ω gate resistor ×2 △ was 220Ω R3,R4 — REMOVED (10kΩ pull-down — TC4427 push-pull replaces) R5 — 10kΩ (voltage divider top · XKC) R6 — 20kΩ (voltage divider bottom · XKC) Total: 18 items · Rev 2 (★ NEW: 5 · △ CHANGED: 3 · REMOVED: 1 pair) ENGINEERING NOTES · Rev 2 1. TC4427 gate driver (Rev 2): Vgs=12V · P_cond=0.56W · P_sw≈0W. No firmware change. Set LEDC to 1kHz (recommended) or any freq ≤100kHz. 2. C1 100nF MLCC must be within 5mm of TC4427 VDD pin. Without it: 60V spike on VDD → IC destroyed on first switch. 3. Source TC4427 from LCSC.com — widely counterfeited on AliExpress. Verify: 3.3V input → gate ≥ 11.5V (measure at MOSFET gate pin). 4. Z1/Z2 (15V zener): clamps Vgs from pump back-EMF spikes. Keep R1/R2 22Ω in series to limit zener peak current. 5. XL4015 output: set to 5.15–5.20V (XKC min VCC = 5.0V sag margin). 6. TSL2591 I2C pull-ups: on-module (breakout) — OK. Bare chip only: add 4.7kΩ resistors from SDA/SCL to 3.3V. REVISION HISTORY Rev 1 — 2026-05-06 — Initial release. Direct 3.3V gate drive (CRIT-1 known). Rev 2 — 2026-05-11 — Option C gate fix: TC4427 dual driver (12V gate); R1/R2 changed 220Ω→22Ω; R3/R4 (10kΩ pull-down) removed; Z1/Z2 15V zener added (Vgs clamp); C1 100nF MLCC bypass added; PSU 10A→15A; XL4015 set 5.15–5.20V; HS1/HS2 heatsinks added. WIRE GAUGE SPECIFICATION · Rev 2 IEC 60364 · Cu @ 40°C · 1.25× safety · Trunks: 0.5m runs · † LED branches: 30cm runs (AWG18 ×4) Segment I (A) I×1.25 Min mm² AWG Actual mm² V-drop @ run V-drop % Notes 12V POWER PSU → Fuse → 12V Bus 10.0 12.5 2.083 12 3.309 0.056V 0.47% Fused 10A; 12 AWG rated 16A @ 40°C 12V Bus → MOSFET#2 → LED junction (trunk) 8.0 10.0 1.667 14 2.081 0.071V 0.60% 8A continuous; 14 AWG trunk (≤0.5m) → splits to 4× AWG18 branches (see †) 12V Bus → MOSFET#1 → Water Pump 2.0 2.5 0.417 18 0.823 0.045V 0.38% Inductive load; 18 AWG rated ~5A 12V Bus → TC4427 VDD 0.015 0.019 0.003 26 0.129 0.002V 0.02% Signal-level; keep short to bypass cap 12V → XL4015 Buck Input 0.25 0.312 0.052 22 0.326 0.014V 0.12% 22 AWG adequate for <0.3A input 5V / 3.3V RAILS 5V Rail → ESP32 VIN 0.5 0.625 0.104 22 0.326 0.029V 0.57% 22 AWG standard for MCU power feed 5V Rail → XKC-Y25-V Sensor 0.05 0.062 0.010 26 0.129 0.007V 0.14% Signal-level; shielded if near motor 3.3V → DHT22 / TSL2591 0.05 0.062 0.010 26 0.129 0.007V 0.22% 3.3V rail; shielded near motor recommended GND RETURNS GND return (main trunk) 10.0 12.5 2.083 12 3.309 0.056V 0.47% MUST match 12V+ trunk gauge GND return (LED trunk + 4× branches) 8.0 10.0 1.667 14 2.081 0.071V 0.60% 14 AWG trunk; AWG18 returns per branch (mirrors supply) — see † GND return (pump) 2.0 2.5 0.417 18 0.823 0.045V 0.38% Match pump supply gauge GND return (5V/sensors) 0.6 0.75 0.125 22 0.326 0.034V 0.68% Match 5V rail supply gauge ALL SEGMENTS PASS — No segment exceeds 3% V-drop. Max in trunk: 0.68% (GND 5V/sensors). Max in † LED branch (AWG18 × 30cm × 5.4A WS2815 peak): 0.57%. WIRE SUMMARY: 12 AWG (3.31 mm²) — 12V trunk + GND trunk (10A paths) 14 AWG (2.08 mm²) — LED trunk (MOSFET#2 → junction) + GND return (8A paths, ≤0.5m) 18 AWG (0.82 mm²) — Water pump + pump GND return (2A paths) · † 4× LED branches AWG18 × 30cm each (1.2A static / 5.4A peak per branch, V-drop ≤0.57%) 22 AWG (0.33 mm²) — 5V rail, ESP32 VIN, buck input, 5V GND return (<0.6A paths) 26 AWG (0.13 mm²) — TC4427 VDD, sensors, 3.3V rail (<50mA signal paths) DESIGN NOTES: 1. Use stranded copper for all runs (flexibility in compact enclosure). 2. Silicone-insulated wire (105°C rating) recommended near LED heat sinks. 3. Voltage drop calculated round-trip. Trunks: 0.5m each way = 1.0m total. † LED branches: 30cm each way = 0.6m total (AWG18 × 4 branches). ρ(Cu@40°C) = 1.86×10⁻⁸ Ω·m. 4. GND return gauge MUST match corresponding supply rail — never use thinner wire on the return path. 5. All gauges include 1.25× continuous current derating per IEC 60364 for 40°C ambient enclosed wiring. 6. † LED branch verification (per strip @ WS2815 all-white peak): AWG18 × 30cm × 5.4A → V-drop = 5.4 × 0.021 Ω/m × 0.6m = 0.068V (0.57%) ✓. AWG18 chassis ampacity ≥ 16A — comfortably above 5.4A peak.
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