Ender3PWM — Quiet PSU Fan Controller

Ender3PWM is a small hardware and firmware project for making the PSU fan in an Ender 3 Pro / P360W24 24V power supply much quieter.

The project replaces the original noisy PSU fan with a larger 80 mm 4-pin PWM fan, controlled by an mbed LPC1768 and a DS18B20 temperature sensor.

The goal is not to remove cooling.
The goal is safe, temperature-controlled and quieter PSU cooling.

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Overview

The system consists of:

• P360W24 24V PSU
• MP1584EN buck converter for 12V fan power
• TSR 1-2450 24V → 5V regulator for the LPC1768
• mbed LPC1768
• DS18B20 temperature sensor
• P2N2222AG NPN transistor for PWM pull-down control
• 80 mm 4-pin PWM fan
• 3D printed PSU cover / fan mount

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Repository structure

Ender3PWM/
├─ main.cpp
├─ README.md
├─ ATTRIBUTION.md
├─ LICENSE
├─ .gitignore
├─ docs/
│  ├─ BOM.md
│  ├─ WIRING.md
│  ├─ BUILD_AND_FLASH.md
│  ├─ TROUBLESHOOTING.md
│  ├─ SAFETY.md
│  └─ KICAD.md
├─ 3D/
│  ├─ README.md
│  ├─ fan_guard_80.stl
│  ├─ Cheng_liang_24v_360w_80mm_fan.stl
│  └─ Cheng_liang_24v_360w_cover.stl
└─ pic/
   ├─ README.md
   ├─ banner.png
   ├─ schematics.png
   ├─ electronic.jpg
   ├─ fancover.jpg
   ├─ pin_configuration_of_5v_fans.jpeg
   ├─ pin_configuration_of_12v_fans.jpeg
   ├─ pin_configuration_of_24v_fans.jpeg
   └─ pin_configuration_of_chromax_black_fan.png

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How it works

P360W24 PSU 24V
├─ MP1584EN 24V → 12V → fan +12V
└─ TSR 1-2450 24V → 5V → LPC1768 VIN

LPC1768 p21 → 1.2kΩ → P2N2222AG base
P2N2222AG collector → fan PWM
P2N2222AG emitter → common GND

DS18B20 DATA → LPC1768 p15
DS18B20 VCC  → LPC1768 3.3V
DS18B20 GND  → common GND

The 4-pin fan receives constant 12V.
Only the fan's PWM control wire is modulated.

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Safety warning

⚠️ The PSU contains mains voltage.
⚠️ Disconnect mains power and wait before opening or modifying the PSU.
⚠️ Do not remove the PSU fan without replacing it with a safe cooling solution.
⚠️ PWM must only be applied to the fan PWM wire, not the 12V fan power wire.
⚠️ All low-voltage grounds must share a common reference.

Read more in docs/SAFETY.md.

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Hardware

See the full bill of materials:

docs/BOM.md

Short version:

Part	Purpose
LPC1768	Controller
DS18B20	Temperature sensing
MP1584EN	24V → 12V fan supply
TSR 1-2450	24V → 5V controller supply
P2N2222AG	PWM pull-down transistor
1.2kΩ	Base resistor
100kΩ	Base pulldown
4.7kΩ	DS18B20 pull-up
80 mm PWM fan	PSU cooling

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Wiring

See the wiring guide:

docs/WIRING.md

Diagram:

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Firmware

The firmware is located in:

main.cpp

It does the following:

• Reads temperature from the DS18B20
• Sets the DS18B20 to faster 10-bit mode
• Generates 25 kHz PWM on p21
• Uses inverted PWM because of the P2N2222AG pull-down transistor
• Fail-safe: sensor error = fan 100%
• Startup safety: fan 100% for 5 seconds
• Serial debug output

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Build and flash

See the full guide:

docs/BUILD_AND_FLASH.md

Short version:

mbed-tools compile -m LPC1768 -t GCC_ARM

Find the generated .bin file and copy it to the MBED drive.

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3D printed parts

STL files are located in:

3D/

See:

3D/README.md

External Thingiverse sources are listed in:

ATTRIBUTION.md

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Debug

Example serial output:

STATUS | Raw: 24.8 C | Filtered: 24.8 C | Target: 35% | Fan: 35% | p21 duty: 65% | p21 avg: 2145 mV

If the fan or sensor does not behave correctly, see:

docs/TROUBLESHOOTING.md

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Project status

This project was built as a practical quiet cooling mod for a 3D printer PSU.

Built by Thomas / TuxiNet.dk