rack-fan-controller/README.md

Rack Fan Controller

ESP32-C6 based smart rack/cabinet fan controller with temperature monitoring, automatic PWM fan speed control, and Home Assistant integration via ESPHome.

Features

• 3-zone fan control: Intake, Central, Outtake (2 fans per zone, 6 total)
• Temperature monitoring: 3x DS18B20 sensors (one per zone)
• RPM monitoring: Tachometer reading from one fan per zone
• Auto speed control: Temperature-based PWM ramping with configurable thresholds
• Negative pressure: Outtake fans run slightly faster for dust control
• 1.47" LCD display: Real-time temps, RPMs, and fan duty on Waveshare ST7789
• Home Assistant: Full integration via ESPHome native API
• USB-C powered: 65W PD charger -> ZY12PDN 12V trigger -> fans + ESP32

Hardware

Component	Qty	Notes
Waveshare ESP32-C6 LCD 1.47"	1	No-touch version, ST7789 172x320
Arctic P12 PWM 120mm	6	4-pin, 2 per zone
ZY12PDN USB-C PD trigger	1	Set to 12V output
LM2596 buck converter	1	12V -> 5V for ESP32
DS18B20 waterproof probe	3	1m cable, 1-Wire bus
PWM Y-splitter (4-pin)	3	1-to-2 per zone
KF301 screw terminals	10	PCB connections
4.7kOhm resistor	1	DS18B20 pull-up
5x7cm prototype PCB	1	Main board

GPIO Mapping (Waveshare ESP32-C6 LCD 1.47")

LCD (occupied - do not use)

Function	GPIO
LCD MOSI	6
LCD CLK	7
LCD CS	14
LCD DC	15
LCD RST	21
LCD BLK	22
RGB LED	8
SD MISO	5
SD CS	4

Project Pin Assignment

Function	GPIO	Notes
PWM Intake	0	Zone 1 - via Y-splitter to 2 fans
PWM Central	1	Zone 2 - via Y-splitter to 2 fans
PWM Outtake	2	Zone 3 - via Y-splitter to 2 fans
Tach Intake	3	RPM from 1 fan in zone 1
Tach Central	10	RPM from 1 fan in zone 2
Tach Outtake	11	RPM from 1 fan in zone 3
DS18B20 bus	9	All 3 sensors on single 1-Wire bus

Wiring Diagram

USB-C PD Charger (65W+)
    |
    USB-C cable
    |
    v
ZY12PDN (set to 12V) ----+------ 12V Rail
    |                     |
    v                     +--- Y-splitter --- Fan1 + Fan2 (INTAKE)
LM2596 (out=5V)           |                   |
    |                     +--- Y-splitter --- Fan3 + Fan4 (CENTRAL)
    v                     |                   |
ESP32-C6 (5V in)          +--- Y-splitter --- Fan5 + Fan6 (OUTTAKE)
    |
    +-- GPIO0 (PWM) ----> Intake splitter PWM pin
    +-- GPIO1 (PWM) ----> Central splitter PWM pin
    +-- GPIO2 (PWM) ----> Outtake splitter PWM pin
    |
    +-- GPIO3 (TACH) <--- Fan1 tach (yellow wire)
    +-- GPIO10 (TACH) <-- Fan3 tach (yellow wire)
    +-- GPIO11 (TACH) <-- Fan5 tach (yellow wire)
    |
    +-- GPIO9 (1-Wire) --+-- DS18B20 (intake)
                          +-- DS18B20 (central)
                          +-- DS18B20 (outtake)
                          |
                         4.7k pull-up to 3.3V

4-Pin Fan Connector Pinout

Pin 1 (Black)  = GND
Pin 2 (Yellow) = +12V
Pin 3 (Green)  = Tach (RPM signal)
Pin 4 (Blue)   = PWM control

Temperature Control Logic

Temp Range	Intake	Central	Outtake	Notes
< 28C	20%	20%	25%	Near-silent baseline
28-35C	20-50%	20-50%	25-55%	Gentle ramp
35-42C	50-80%	50-80%	55-85%	Medium cooling
42-50C	80-100%	80-100%	85-100%	Full cooling
> 50C	100%	100%	100%	Emergency + HA alert

Outtake always runs +5% over intake for slight negative pressure (dust control).

Build & Flash

# Install ESPHome
pip install esphome

# Validate config
esphome config esphome/rack-fan-controller.yaml

# Flash (first time via USB)
esphome run esphome/rack-fan-controller.yaml

# Subsequent updates via OTA
esphome run esphome/rack-fan-controller.yaml --device rack-fan-ctrl.local

Home Assistant

After flashing, the device auto-discovers in HA via ESPHome integration. Exposed entities:

• sensor.rack_temp_intake / central / outtake
• sensor.rack_fan_rpm_intake / central / outtake
• sensor.rack_fan_duty_intake / central / outtake
• switch.rack_fan_auto_mode (enable/disable auto control)
• number.rack_fan_target_temp (target temperature setpoint)
• number.rack_fan_min_duty / max_duty (manual override range)

License

MIT