I designed a fan controller for my 10in rack. I used Easy HomeMade Projects design and modified it for my needs. 
 

I modified the code to my needs

The Arduino boots up and runs a learn sequence for the PWM fans. It defaults to an auto setting after boot up which gradually adjusts the fan speed from OFF under 70F to full speed above 90F. The push button can also toggle between AUTO, HI, MED, and LOW speed settings.

My code [https://docs.google.com/document/d/16pxGutbBggcqQ_DtfyWDRvfJyZrs05g55ypvQSzxjFs/edit?usp=sharing](https://docs.google.com/document/d/16pxGutbBggcqQ_DtfyWDRvfJyZrs05g55ypvQSzxjFs/edit?usp=sharing)

I bent the positive pin up on the barrel jack and ran the power through the toggle switch first then back to the pad on the circuit board. I also ran a wire from GND to the momentary switch then to D3 for the mode switching. I also designed a replacement button for the push button.

I included the fusion file so you can add whatever you want to the right of the fan controller area. I made one with keystone jacks and one for my omada controller.

I used the parts listed in Easy HomeMades Projects video 

additional materials needed
1 Toggle switch       [https://tinyurl.com/2e4hnwtc](https://tinyurl.com/2e4hnwtc)

1 push button         [https://tinyurl.com/ywr8tf23](https://tinyurl.com/ywr8tf23)

4 Wire PWM fans

4 jumper wires to mount the OLED remotely 

3 or 4 M2 screws to mount the PCB

I also used this power supply [https://www.amazon.com/dp/B077PW5JC3?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1](https://www.amazon.com/dp/B077PW5JC3?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1)