Community project
Temperature-Controlled Fan Hub
This temperature-controlled fan hub uses an ESP32-S3 to monitor thermal conditions and automatically adjust fan speeds based on real-time temperature readings. The system reads analog voltage from NTC thermistors, converts those readings to temperature values, and drives up to three 12 V PC fans via PWM-controlled transistor switches. A 5 V linear regulator powers the ESP32 from the same 12 V supply that feeds the fans, keeping the entire system on a single power input.
This guide provides a complete wiring diagram, full parts list with sourcing guidance, ESPHome firmware ready to customize, and step-by-step assembly instructions. Builders will learn how to condition analog sensor signals, implement thermal control logic, and safely switch higher-voltage loads from a microcontroller. The project is suitable for cooling enclosures, server racks, or any application requiring temperature-responsive fan management.
Wiring diagram
Gather all the parts
Assemble it in 7 steps
1. Place the 5 V regulator parts
With the 12 V supply unplugged, place the 7805 with its labelled face toward you. For the usual TO-220 7805 package, the left pin is IN, middle pin is GND, and right pin is OUT; check the printing or datasheet for your exact part before connecting it. Bolt regulator_heatsink to regulator_7805’s metal tab so it can release heat.
- Keep the regulator and its heatsink clear of wires and plastic.
- The 7805 must be a positive 7805/LM7805, not the negative 7905 originally shown.
- Do not power the circuit if the regulator pins are uncertain — swapping IN and OUT can damage the regulator and ESP32.
2. Add the regulator capacitors
Connect c1_input’s positive lead to the regulator IN pin and its negative striped lead to GND (input smoothing). Connect c2_output across the regulator output: one lead to OUT and the other to GND (output stability). Keep both capacitors physically close to the regulator pins.
- The 10 µF capacitor has polarity: its stripe marks the negative lead.
- The 100 nF ceramic capacitor has no polarity.
- Putting the 10 µF capacitor in backwards can make it overheat or burst.
3. Connect the shared 12 V supply
Connect the 12 V supply positive output to regulator_7805 IN and to the 12V wire on fan_1, fan_2, and fan_3 (power). Connect the supply negative output to the shared GND line (ground). This one supply feeds the fans directly and feeds the regulator separately.
- Use a 12 V supply rated for at least the three fans’ combined start-up current plus 0.5 A for the ESP32 regulator.
- Use thicker wire for the fan 12 V and GND connections than for the signal wires.
- Never connect the 12 V positive wire to an ESP32 pin, including 5V, 3V3, or any GPIO — this can permanently damage the board.
4. Power the ESP32 from the regulator
Connect regulator_7805 OUT to the ESP32-S3 Zero 5V/VIN pin (power). Connect regulator_7805 GND to an ESP32 GND pin (ground). The fan-supply negative, all fan grounds, transistor emitters, and ESP32 GND must be one shared ground connection.
- Measure between OUT and GND with a multimeter before attaching the ESP32; it should read close to +5 V.
- The 7805 heatsink may become warm in normal use.
- Do not connect the regulator OUT wire to the ESP32 3V3 pin — 5 V on that pin can permanently damage the board.
5. Build the five temperature probe junctions
For each probe, connect one NTC lead to ESP32 3V3 (power). Connect its other lead to its matching 10 kΩ resistor and the assigned GPIO (signal); connect the resistor’s other lead to GND (ground). Use GPIO1 for ntc_1, GPIO2 for ntc_2, GPIO3 for ntc_3, GPIO4 for ntc_4, and GPIO5 for ntc_5.
- The NTC probe leads have no polarity.
- Keep each probe’s signal junction away from the 12 V wiring.
- Do not connect an NTC signal junction to 12 V — ESP32 inputs accept only low-voltage signals.
6. Add the three fan control connections
For each fan, connect GPIO6 through base_r1 to pwm_q1 base, GPIO7 through base_r2 to pwm_q2 base, and GPIO8 through base_r3 to pwm_q3 base (control signals). Connect every transistor emitter to GND and each collector to its fan’s PWM wire. Connect fan_1 TACH to GPIO14 and tach_pullup_r1 to 3V3; fan_2 TACH to GPIO15 and tach_pullup_r2 to 3V3; and fan_3 TACH to GPIO17 and tach_pullup_r3 to 3V3 (speed signals).
- PWM is commonly the blue fan wire and TACH commonly green, but confirm with the fan’s label or datasheet.
- The onboard RGB status LED remains on GPIO16; do not connect a fan wire to GPIO16.
- Do not connect a fan PWM or TACH wire straight to the ESP32; the transistor and 3.3 V pull-up parts protect the ESP32 from higher fan signal voltages.
7. Inspect and power safely
Before switching on, verify that only fan wires and regulator IN receive +12 V, while regulator OUT alone goes to the ESP32 5V/VIN pin. Confirm every ground wire is joined. Turn on the 12 V supply, check the regulator output remains near 5 V, then power the firmware from the same board connection only after this check.
- If the 7805 becomes too hot to touch briefly, switch off immediately and use a larger heatsink or a 5 V buck converter.
- Use Schematik’s Deploy button to flash the firmware after the wiring is complete.
- Disconnect power immediately if a wire heats up, you smell hot plastic, or the regulator output is not close to 5 V.
Review all connections
1. Connections between "ntc_1" and "ESP32"
2. Connections between "ntc_ref_r1" and "ESP32"
3. Connections between "ntc_2" and "ESP32"
4. Connections between "ntc_ref_r2" and "ESP32"
5. Connections between "ntc_3" and "ESP32"
6. Connections between "ntc_ref_r3" and "ESP32"
7. Connections between "ntc_4" and "ESP32"
8. Connections between "ntc_ref_r4" and "ESP32"
9. Connections between "ntc_5" and "ESP32"
10. Connections between "ntc_ref_r5" and "ESP32"
11. Connections between "base_r1" and "ESP32"
12. Connections between "pwm_q1" and "ESP32"
13. Connections between "base_r2" and "ESP32"
14. Connections between "pwm_q2" and "ESP32"
15. Connections between "base_r3" and "ESP32"
16. Connections between "pwm_q3" and "ESP32"
17. Connections between "fan_supply" and "ESP32"
18. Connections between "fan_1" and "ESP32"
19. Connections between "tach_pullup_r1" and "ESP32"
20. Connections between "fan_2" and "ESP32"
21. Connections between "tach_pullup_r2" and "ESP32"
22. Connections between "tach_pullup_r3" and "ESP32"
23. Connections between "fan_3" and "ESP32"
24. Connections between "regulator_7805" and "ESP32"
25. Connections between "c1_input" and "ESP32"
26. Connections between "c2_output" and "ESP32"
Deploy the firmware
# GPIO16 drives the Waveshare ESP32-S3-Zero onboard WS2812 status LED.
esphome:
name: s3-zero-fan-controller
friendly_name: S3 Zero Fan Controller
on_boot:
priority: -100
then:
- light.turn_on:
id: status_led
red: 0%
green: 0%
blue: 100%
brightness: 25%
esp32:
variant: esp32s3
framework:
type: arduino
logger:
api:
wifi:
ap:
ssid: "S3 Fan Controller Setup"
password: "fancontrol"
captive_portal:
light:
- platform: esp32_rmt_led_strip
id: status_led
name: "Controller Status LED"
pin: GPIO16
num_leds: 1
chipset: WS2812
rgb_order: GRB
restore_mode: ALWAYS_OFF
binary_sensor:
- platform: status
name: "Controller Connection"
id: controller_connection
on_press:
then:
- light.turn_on:
id: status_led
red: 0%
green: 100%
blue: 0%
brightness: 20%
on_release:
then:
- light.turn_on:
id: status_led
red: 100%
green: 0%
blue: 0%
brightness: 20%
output:
- platform: ledc
id: fan1_pwm
pin: GPIO6
frequency: 25000 Hz
- platform: ledc
id: fan2_pwm
pin: GPIO7
frequency: 25000 Hz
- platform: ledc
id: fan3_pwm
pin: GPIO8
frequency: 25000 Hz
sensor:
- platform: adc
id: ntc1_voltage
pin: GPIO1
attenuation: 12db
update_interval: 5s
- platform: resistance
id: ntc1_resistance
sensor: ntc1_voltage
configuration: DOWNSTREAM
resistor: 10kOhm
- platform: ntc
name: "Temperature 1"
id: temperature_1
sensor: ntc1_resistance
calibration:
b_constant: 3590
reference_temperature: 25°C
reference_resistance: 10kOhm
- platform: adc
id: ntc2_voltage
pin: GPIO2
attenuation: 12db
update_interval: 5s
- platform: resistance
id: ntc2_resistance
sensor: ntc2_voltage
configuration: DOWNSTREAM
resistor: 10kOhm
- platform: ntc
name: "Temperature 2"
id: temperature_2
sensor: ntc2_resistance
calibration:
b_constant: 3590
reference_temperature: 25°C
reference_resistance: 10kOhm
- platform: adc
id: ntc3_voltage
pin: GPIO3
attenuation: 12db
update_interval: 5s
- platform: resistance
id: ntc3_resistance
sensor: ntc3_voltage
configuration: DOWNSTREAM
resistor: 10kOhm
- platform: ntc
name: "Temperature 3"
id: temperature_3
sensor: ntc3_resistance
calibration:
b_constant: 3590
reference_temperature: 25°C
reference_resistance: 10kOhm
- platform: adc
id: ntc4_voltage
pin: GPIO4
attenuation: 12db
update_interval: 5s
- platform: resistance
id: ntc4_resistance
sensor: ntc4_voltage
configuration: DOWNSTREAM
resistor: 10kOhm
- platform: ntc
name: "Temperature 4"
id: temperature_4
sensor: ntc4_resistance
calibration:
b_constant: 3590
reference_temperature: 25°C
reference_resistance: 10kOhm
- platform: adc
id: ntc5_voltage
pin: GPIO5
attenuation: 12db
update_interval: 5s
- platform: resistance
id: ntc5_resistance
sensor: ntc5_voltage
configuration: DOWNSTREAM
resistor: 10kOhm
- platform: ntc
name: "Temperature 5"
id: temperature_5
sensor: ntc5_resistance
calibration:
b_constant: 3590
reference_temperature: 25°C
reference_resistance: 10kOhm
- platform: pulse_counter
name: "Fan 1 Speed"
pin:
number: GPIO14
mode:
input: true
pullup: false
unit_of_measurement: "RPM"
accuracy_decimals: 0
count_mode:
rising_edge: INCREMENT
falling_edge: DISABLE
filters:
- multiply: 0.5
- platform: pulse_counter
name: "Fan 2 Speed"
pin:
number: GPIO15
mode:
input: true
pullup: false
unit_of_measurement: "RPM"
accuracy_decimals: 0
count_mode:
rising_edge: INCREMENT
falling_edge: DISABLE
filters:
- multiply: 0.5
- platform: pulse_counter
name: "Fan 3 Speed"
pin:
number: GPIO17
mode:
input: true
pullup: false
unit_of_measurement: "RPM"
accuracy_decimals: 0
count_mode:
rising_edge: INCREMENT
falling_edge: DISABLE
filters:
- multiply: 0.5
- platform: template
name: "Hottest Temperature"
id: hottest_temperature
unit_of_measurement: "°C"
device_class: temperature
state_class: measurement
accuracy_decimals: 1
update_interval: 5s
lambda: |-
float hottest = -100.0f;
if (!isnan(id(temperature_1).state)) hottest = max(hottest, id(temperature_1).state);
if (!isnan(id(temperature_2).state)) hottest = max(hottest, id(temperature_2).state);
if (!isnan(id(temperature_3).state)) hottest = max(hottest, id(temperature_3).state);
if (!isnan(id(temperature_4).state)) hottest = max(hottest, id(temperature_4).state);
if (!isnan(id(temperature_5).state)) hottest = max(hottest, id(temperature_5).state);
return hottest > -100.0f ? hottest : NAN;
number:
- platform: template
name: "Manual Fan Speed"
id: manual_fan_speed
unit_of_measurement: "%"
icon: "mdi:fan"
min_value: 30
max_value: 100
step: 1
optimistic: true
restore_value: true
initial_value: 50
set_action:
- switch.turn_off: automatic_fan_control
- lambda: |-
float fan_duty = x / 100.0f;
// The transistor inverts the 4-wire fan PWM signal.
float transistor_duty = 1.0f - fan_duty;
id(fan1_pwm).set_level(transistor_duty);
id(fan2_pwm).set_level(transistor_duty);
id(fan3_pwm).set_level(transistor_duty);
switch:
- platform: template
name: "Automatic Fan Control"
id: automatic_fan_control
optimistic: true
restore_mode: RESTORE_DEFAULT_ON
interval:
- interval: 5s
then:
- lambda: |-
if (!id(automatic_fan_control).state) return;
float hottest = id(hottest_temperature).state;
float fan_duty = 1.0f;
if (!isnan(hottest)) {
if (hottest <= 30.0f) fan_duty = 0.30f;
else if (hottest >= 60.0f) fan_duty = 1.0f;
else fan_duty = 0.30f + (hottest - 30.0f) * 0.70f / 30.0f;
}
float transistor_duty = 1.0f - fan_duty;
id(fan1_pwm).set_level(transistor_duty);
id(fan2_pwm).set_level(transistor_duty);
id(fan3_pwm).set_level(transistor_duty);Remix this project
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