3D Printer FAN PWM NOISE 100% Elimination

In this instructable/video, I am making a 3D Printer Fan PWM Noise FIX that completely eliminates that extremely annoying noise. I will explain why it happens and show the possible solutions to fix it.

Step 1: Things That DON'T WORK

I hate that fan PWM noise so much…And to suppress it "mechanically/physically" is a really hard task. Yes, it is silly to do it with a suppressor which is like a prop, but even designs that are somewhat made to silence the fan don’t do anything here. Not to mention that some even heavily lower the airflow.

Step 2: The Problem

So to fix the problem, we need to understand it first. You see, your 3D printer sends a pulsed power signal to the fan and it is called PWM. It switches power ON and OFF very quickly and the longer the ON signal lasts the faster the fan spins. But if that ON and OFF switching frequency is not fast enough and it falls within the human audible range – you probably can guess – you hear that annoying noise.

Step 3: Two Ways to Solve It

So, this means there are two possible fixes. We have to increase the frequency or eliminate the pulsations.

The frequency can be changed in some 3D printers’ firmware. But that requires knowledge about editing, compiling, and flashing it to your printer. Not only that, if components inside are not designed for the higher frequency they can be damaged. And this is not even a universal solution.

Well then, this means that reducing pulsations is the way. And the easiest way to do that is to make a basic electronic circuit.

Step 4: Advantages & Disadvantages of the Circuit

So obviously the advantage is that it completely eliminates that insanely irritating fan PWM noise. But it is not all sunshine and roses. There will be a few small disadvantages.

The first one is that we will lose around 10% of the fan performance. And the more powerful the fan the bigger the voltage drop we will get and more energy will be wasted through the resistor.

The second one is that the fan speed percentage will not be linear. What this means is that with the circuit installed, when you set the fan speed to 5% you will get 22% when compared to before. With 10% around 36% and with 50% around 77%, well you get the point.

This doesn’t really change much as you will only have to roughly know the corresponding values and update them in your slicer profiles. But I will take those few disadvantages any day of the week as having a printer with that high pitch whining noise is extremely annoying…

Step 5: Janky Way of Making It

So how to make the circuit? And there are two very different ways. The first one is a little bit janky as you need to solder one component to another in mid-air always checking the schematics where which lead goes. That will end up in not the prettiest solution but it will do the trick.

Step 6: Proper Way of Making It

The second way is to use a custom printed circuit board. The advantage of this way is that it is extremely easy to solder components and the final result is very professional and easy to use. Obviously, it will cost more.

If you want you can order the PCB very easily, I published the PCB as the project here (PCBWay is a sponsor of the video) - https://bit.ly/EasyProjectOrder

Or you can download Gerber files and order from your favorite PCB maker, it is up to you.

To install it just cut the cooling fan wire, trim the insulation, and secure wires from the printer to V-in and from the fan to the V-out terminals. And this is pretty much it.

Step 7: The Components

Components that you will need:

2x KF-128-2P 3.81MM screw terminals for wires (marked as Vin and Vout in the schematics). They have 3.81-millimeter pin spacing that goes into the PCB (you don’t need these if you choose the first option). Link - https://s.click.aliexpress.com/e/_DcJ0DzV
1x1N5819 Schottky diode (marked as R1 in the schematics, max current 1A). They allow current to flow only in one direction, but they add a small voltage drop (the slight reduction in max fan speed). If you can’t find these you can use SB160 diodes. And if you can’t find these you can use a regular 1N4007 diode (but this one will have a bigger voltage drop of ~0.7V compared to previous ones of ~0.4V). Product link - https://s.click.aliexpress.com/e/_DFlOhgL
1x35V 220uF electrolytic capacitor (marked as C1 in the schematics). For fans of 0.5-1.5W, you can use a smaller capacity 35V 220uF one. For fans above 1.5W use a 35V 330uF one, it will be the same diameter only taller. Product link - https://s.click.aliexpress.com/e/_DBqo2ht
1x3W 51 Ohm resistor. For 12V 3D printers use a 3W 25-Ohm resistor. For 24V 3D printers use a 3W 51-Ohm resistor. Product link - https://s.click.aliexpress.com/e/_DFMHoGf

Step 8: Cautions of the Project

To end the instructable let’s talk about the cautions of this project to be aware of. Some 3D printer boards are made to cut down the cost so much and they can come with extremely weak components. However, after checking multiple original boards from popular 3D printers, I can say that this is more exception than the rule.

The most optimal way is just to open the bottom of the printer and check out what MOSFETs are near your 3d printer fans. Then you can google the name of it and from a datasheet know how many amps they can handle, anything above 2 amps is more than enough.

Step 9: Voltages of the Fans & Resistor Values

The last thing that I want to talk about is the compatibility with different fans. Either 12 or 24V fans will work with this circuit, just make sure to use the correct resistor value for those different voltages. In both configurations, the resistor limits the current to around 500mA.

You can use a lower value resistor to reduce the drop of the max fan speed, but remember that the maximum current during the charge of the capacitor will also increase. So don’t go crazy as there will be less and less benefit with lower value resistors. Not to mention that the used Schottky diode has a rating of 1A in the first place.

Step 10: Wattages of the Fans

Now the wattages of the fans. If your fan is around 1.2W then use a semi-closed enclosure as the resistor will get only slightly warm (14-22C above room temp).

And if your fan is twice as powerful at around 2.4W then use an open-style enclosure as the resistor will get pretty hot (30-40C above room temp).

Ideally, you want to find a spot where you get at least some airflow from the mainboard cooling fan.

Step 11: There Always Will Be Weird Fans That Won't Work

And the absolute last thing to mention is the incompatible fans. The craziest part of this is that I tested many fans and all of them work perfectly. The ones that didn’t work are those from the Kingroon KP3S 3D printers that I made this fix for. Like really??

They have this extremely weird issue. Everything is fine until you turn the speed way down, then they turn off (but still draw 2W), and the resistor temperature just skyrockets…

So yeah… just be aware that some weird no-name fans won’t work. But again it is more exception than the rule, same as with the weak 3d printer components.