What is it?

This is a fan controller that allows you to change both the PWM signal your motherboard sends to any 4-pin fan (which tells the fan how fast it should be running) as well as the tachometer signal your fan sends back (to tell the motherboard how fast it's actually running). This is useful for e.g. server motherboards or other equipment that requires fast and noisy fans to be installed and will not boot if you replace these fans by quieter models (that turn too slowly according to the motherboard). This fan controller fools your motherboard into thinking your fan is going faster than it actually is.

Note that you can also install the fan controller without any fan attached. The motherboard will still sense an RPM signal and think there's a fan attached. This is handy for equipment that you want to make entirely fanless, but throws a fit if you remove the fan even though it's properly cooled otherwise.

When you order this product, you get:

• the board
• a cable to connect it to your motherboard
• and a 3D printed case around it

You can mount it anywhere inside your computer case using e.g. velcro or sticky tape.

I've designed and built this project, but it is completely open source (creative commons), so you can do with it as you like. Check out the github repository here. You can also leave feedback, bug reports and feature requests there.

Why did you make it?

A couple months ago a user on a forum I frequent (Tweakers.net) asked me to make this. As it turns out, right around the same point in time I was doing a project for work that required the same kind of functionality. I found it a useful board to have around, so I decided it would be a nice open source project. A couple of firmware rewrites and revisions later, it's ready for publishing.

What makes it special?

Generally, there are 2 types of fan controllers on the market: either very simple ones that only have a potentiometer (rotating knob) for modifying how fast the fan spins, or very complicated ones that take up a floppy drive or CD-drive slot and have all kinds of fancy displays. Annoyingly, almost none of them have the possibility to modify the RPM signal sent back to the motherboard, which means it's hard to silence otherewise loud machines. The low-end fan controllers are generally analog circuits, i.e. it's hard to reprogram them for specific behaviour.

This fan controller has open source firmware with quite a lot of documentation (for a 2kB microcontroller) and lots of commenting. It should be a breeze for anyone familiar with Atmel microcontrollers to modify the firmware as you please.

The boards are designed using entirely open source software (TinyCAD and FreePCB), so if you like you can just go ahead and modify the board. For instance if you need to fit your particular fan controller in an oddly-shaped place.

The enclosure is designed in CATIA, which is unfortunately not open source (and kind of expensive). If you want to design your own case, you'll probably have to do it from scratch. I do of course have .stl files in the repository so you can print the case as I designed it.