Note: Backfeeding voltage or leaving the tacho wire unplugged can damage the fan. We highly recommend connecting the fan to a dedicated tacho port when possible. The alternative method, which uses an end stop with a 1n4148 diode, is not beginner-friendly.

If your setup does not require tacho functionality or your tool board lacks a tacho port, we suggest using 2-wire fan variants, especially for older boards like the EBB36/42. Leaving the tacho wire disconnected can cause a short circuit and damage the fan on EBB36/42 boards and some BTT boards.

However, if your tool board supports a tacho header, you won’t encounter these issues as long as the fan is wired correctly to the header. We have tested our Tacho and 4 wire fans on Duet 3D Toolhead Board and Nitehawk.

TABLE OF CONTENTS

• Klipper Guide
• Marlin Guide
• RepRap Guide

Klipper Guide:

Credit: https://ellis3dp.com/Print-Tuning-Guide/articles/useful_macros/hotend_fan_monitoring.html

Credit: https://www.klipper3d.org/Config_Reference.html#heater_fan

Requirements: 

• Machine running klipper
• Spare endstop port/pin (data pin, not GND/5v/3.3v), please refer to your toolhead board pinout or wire to tacho specifically for tacho, as these will have built in diode required.
• 1n4148 diode is required general end stop port, otherwise wire to dedicated tacho header which should have 1n4148 wire inline (double check board schematic)  

Setup: 

Download Ellis Macro: https://github.com/AndrewEllis93/Print-Tuning-Guide/blob/main/macros/fan_tach_monitor.cfg

LDO Tacho Configuration: https://github.com/MotorDynamicsLab/Nitehawk-SB/blob/master/Firmware/Klipper%20Configs/tacho_macros.cfg

1. Under your hotend fan, set "tachometer_pin" (Remember to set pull up to the pin "^" (example: tachometer_pin: ^P1.29 )
2. Place fan_tach_monitor.cfg in the same directory as your printer.cfg.
3. Add [include fan_tach_monitor.cfg] to your printer.cfg.
4. Change min_rpm and max_consecutive_stops in the HOTEND_FAN_CHECK macro to your desired values. (The default value 3000 works well in our testing, you may want test yourself by stopping/slowing the hotend fan when hotend is heated up to pass your minimal toggle fan speed.)
5. Place your desired hotend fan failure g-code in FAN_STOPPAGE_ROUTINE

Marlin Guide:

Requirements: 

• Machine running Marlin
• Spare endstop port/pin (data pin, not GND/5v/3.3v), please refer to your toolhead board pinout or wire to tacho specifically for tacho, as these will have built in diode required. 
• 1n4148 Diode is required general end stop port, otherwise wire to dedicated tacho header which should have 1n4148 wire inline (double check board schematic)  

Within Configuration_adv.h (Find tachometers section)

Find and define E0 fan (in most case, hotend fan setup would be E0 (Extruder 0/1) with endstop/data pin. 

Example: 

#define E0_FAN_TACHO_PIN PIN19

RepRap Guide:

Requirements: 

• Machine running RepRap 
• Wire to Tacho Fan Port, most duet toolhead or main board will have suitable header.

More Information: https://docs.duet3d.com/User_manual/Connecting_hardware/Fans_connecting

Example:

M950 F2 C"out4+out4.tach" ; Fan 2 uses out4, and using out4.tach as a tacho inputM950 F2 C"out4+out4.tach" ; Fan 2 uses out4, and using out4.tach as a tacho inputM950 F2 C"out4+out4.tach" ; Fan 2 uses out4, and using out4.tach as a tacho input