Keep Cool With This Open Source AVR Fan Controller

We’ve all got projects kicking around that we haven’t had time to document for our own purposes, let alone expose to the blinding light of the Internet. There are only so many hours in a day, and let’s face it, building the thing is a lot more fun than taking pictures of it. It took [Matthew Millman] the better part of a decade to combine everything he’s learned over the years to finally document the definitive version of his open source intelligent fan controller, but looking at the final result, we’re glad he did.

At the heart of this board is an ATmega328P, but don’t call it an Arduino. [Matthew] makes it very clear that if you want to hack around with the code for this project, you’re going to need to not only have a programmer for said chip, but know your way around AVR-GCC. He’s provided pre-built binaries for those content to run with the default settings, but you’ve still got to get it flashed onto the chip yourself. The project is designed to use the common DS18B20 temperature sensor, and as an added bonus, the firmware can even check if yours is a bootleg (spoilers: there’s an excellent chance it is).

Arguably the most interesting feature of this fan controller is its command line interface. Just plug into the serial port on the board, open your terminal emulator, and you’ll have access to a concise set of functions for querying the sensors as well as setting temperature thresholds and RPM ranges for the fans. There’s even a built-in “help” function should you forget a command or the appropriate syntax.

Originally [Matthew] developed this project as a way to control multiple fans inside of a PC case, but naturally, things have changed quite a bit since those early days. While today there’s no shortage of fancy controllers that can handle throttling an array of fans based on the internal temperature of your rig, there’s still something to be said for rolling your own solution. More importantly, there’s certainly other potential uses for a fully open source programmable fan controller.

Hacked Case Fan Follows The Leader With IR Sensor

Adding an additional fan to your PC is usually pretty straightforward, but as [Randy Elwin] found, this isn’t always the case with the newer Small Form Factor (SFF) machines. Not only was the standard 80 mm fan too large to fit inside of the case, but there wasn’t even a spot to plug it in. So he had to come up with his own way to power it up and control its speed.

Now if he only needed power, that wouldn’t have been a problem. You could certainly tap into one of the wires coming from the PSU and get 12 V to spin the fan. But that would mean it was running at max speed the whole time; fine in a pinch, but not exactly ideal for a daily driver.

Note the SATA connector pulled from a dead HDD.

To get speed control, [Randy] put together a little circuit using an ATtiny85, an IR LED, and a LTR-306 phototransistor. The optical components are used to detect the GPU fan’s current speed, which itself is controlled based on system temperature. Using the GPU fan RPM as an input, a lookup table on the microcontroller sets an appropriate speed for the 80 mm case fan.

One could argue that it would have been easier to connect a temperature sensor to the ATtiny85, but by synchronizing the case fan to the computer-controlled GPU fan, [Randy] is able to manually control them both from software if necessary. Rather than waiting on the case temperature to rise, he can peg the GPU fan and have the external fan speed up to match when the system is under heavy load.

You may think this is overkill for a simple case fan, but compared to some of the cooling hacks we’ve seen in the past, it’s pretty tame.

Hackers Vs. Mold: Building A Humidistat Fan

Having a mold problem in your home is terrible, especially if you have an allergy to it. It can be toxic, aggravate asthma, and damage your possessions. But let’s be honest, before you even get to those listed issues, having mold where you live feels disgusting.

You can clean it with the regular use of unpleasant chemicals like bleach, although only with limited effectiveness. So I was not particularly happy to discover mold growing on the kitchen wall, and decided to do science at it. Happily, I managed to fix my mold problems with a little bit of hacker ingenuity.

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Colorful Fan And LED Controller For 3D Printer

[Dave] just couldn’t take the ambient noise from his Lulzbot Mini anymore, so he built a fancy fan controller for it.

He measured some points on the printer’s Rambo controller board to see what actually got hot during a print. The hottest components were the motor drivers, so he taped a thermistor to them. He also placed one in the printer’s power supply. He replaced the main fan with a low noise model from Noctua (which have the most insanely fancy packaging you could imagine for a computer fan). The software on an Arduino Nano now idles the fan at an inaudible 650RPM, if an unacceptable temperature increase is detected, it increases the fan speed for a period, keeping everything nice and quietly cool.

The graphics display was added because, “why not?” A classic reason. The graphics runs on a hacked version of Adafruit’s library. It took him quite a while to get the graphics coded, but they add that extra bit of high-tech flair to keep the cool factor of the 3d printer up before they become as ubiquitous as toasters in the home. The code, fritzing board layout, 3D models, and a full build log is available at his site.