Adding a fan to improve air circulation in this filament drier is a common mod. Here is my variation.
The first step is to source a voltage for the fan. The PCB already has unpopulated locations for fan components. I added a connector, diode D2 and a 30V n-channel Mosfet Q1. The gate of Q1 is connected to pin 16 of the MCU. This means the fan will come on when the LCD backlight is on.
![](https://ynformatics.com/wp-content/uploads/2023/07/IMG_6615-300x300.jpg)
I fixed a 4010 24V fan behind the display with hot glue and cut a small opening in the hot plate to let the air circulate. I also wired up an MP1584 buck converter module to allow control of the fan voltage, speed and noise.
![](https://ynformatics.com/wp-content/uploads/2023/07/IMG_6604-300x300.jpg)
And here are the temperature profiles inside the unit measured at the top of a roll of filament. The first run is with the fan set to 12V. The second with no fan.
![](https://ynformatics.com/wp-content/uploads/2023/07/temps-1024x416.jpg)