If your Raspberry Pi 4 project relies on a HAT, you might want to throw in this stackable Smart Fan HAT by Sequent Microsystems. It cools far more than a single heatsink and has complete access to GPIO.
For the Pi 4, fan HATs are already available, but the largest draw for this one is the fully exposed access to the GPIO pins. Users can stack several HATs together because the full set of pins is exposed on top.
The equipment is as wide as the Raspberry Pi 4. The HAT, receiving input from the I2C interface, uses its own 32-bit processor. A step-up power supply is essential to convert the 5V output from the Pi to 12V.
It is possible to stack too many HATs, according to the Dev team, further compounding the heat problem. For maximum cooling efficiency, makers can splice multiple Smart Fan HATs into a HAT stack if necessary.
On Kickstarter, the team recently met their funding goal; you can read more about the HAT and what to expect on the project page. For more cool creations from the producer community, be sure to check out our list of Best Raspberry Pi Projects.