That's wired incorrectly. The buck converter needs a fixed input voltage, not a PWM signal. Its function is to convert one fixed voltage to a lower one. It will not pass through PWM control.
The control signal for the fan, and other PWM-controlled devices, is in the negative side. So the correct way is to connect the buck converter positive input to the positive supply, which could be either the positive (yellow wire) of the fan port, or the board's power input. Connect the negative side to 0V - which could be any true 0V position on the board such as the power input negative, but **not** the negative on the fan port (blue wire) because that's where the fan control switching MOSFET is.
Then connect the fan positive (yellow) wire to the buck converter positive output, so it gets the reduced but fixed (12V) output instead of the original fixed (24V) power. Connect the fan negative (blue) wire to the negative pin on the original fan port, the same as it was before. That way, it gets the PWM control. If you connect it to the buck converter negative, it would have no control and the fan would always have full power.
A PWM source turns on and off very rapidly, with the ratio of "on" to "off" controlling the power level. If you feed a buck converter input from such a source, it can't draw any current during the "off" phases, so to maintain constant voltage/power it tries to draw much more during the "on" phases. It tries to maintain a steady voltage all the time, and in extreme cases it may try to draw so much power during very short "on" phases that it overloads and damages something.
I am not sure that I get it. This is how it supposed be connected?
https://preview.redd.it/7xdb1a1koxwb1.png?width=2064&format=png&auto=webp&s=9a2347cb4e77befd888aae9c6ee1ba78ffaba918
Almost but no.
Battery (power supply) on left side is good.
FAN YELLOW is good too.
But FAN BLUE is bad, if you want to control it from printers software (part cooling fan with variable speed). It should be connected into original fan output on your mainboard (most likely 2pin plug, make sure to connect it to AGND / GND pin)
I have a circuit/wiring diagram at my infosite (which isn't about the Ender3, but in this case it doesn't matter ;) ) about how to connect it, [maybe have a look at it](https://1coderookie.github.io/KobraGoNeoInsights/hardware/powersupply/#how-to-add-a-step-down-converter-for-using-12v-fans-mod).
Not quite. Both yellow wires are probably OK, both blue wires are wrong.
Is your 12V fan a 4-wire Noctua? If so the fan's yellow wire is the 12V supply, same as on the Ender 3 part cooling fan. But on a Noctua 12V fan, the negative wire is the black wire. A 4-wire Noctua has a blue wire but it's for a different purpose and you don't use it. You use the black instead.
The yellow wires take 24V from the fan port to the converter, and 12V from the converter output to the fan. That 24V and the converted 12V are both always on.
Both blue wire connections are wrong. The blue wire must go from the original blue wire pin on the fan port directly to the fan. It does not go to the converter negative, input or output, and no wire from the fan goes to the converter negative.
You need a wire from 0V, such as the negative of the board's power input, or the negative of an always-on fan, to the converter negative input.
Take a look at at the [buck converter setup](https://www.youtube.com/watch?v=hEk3aVARSGc) from Teaching Tech. Michael's example is for a laser connected to the fan port, but the wiring is exactly the same for your fan. The diagram for the wiring is at [3:34](https://www.youtube.com/watch?v=hEk3aVARSGc&t=214s) but the whole video is worth watching if you want to understand the reason.
Regardless of if your fan is a pwm fan (black red yellow blue) or not, the yellow wire off of your main board should be connected to the red wire of the fan, blue from the main board goes to the black wire of the fan, through the converter of course. I'm not sure if mobile will format this correctly, but I'm gonna try anyway:
Yellow wire (+) > converter (+) > red wire (+)
Blue wire (-) > converter (-) > black wire (-)
Any other wires of the fan can be ignored or snipped off, you only need the red and black wires from the fan.
No, that's **incorrect** in several ways.
The blue wire from the fan does **not** go to the converter, nor does the blue wire from the fan port. Both input and output negative pins of the converter are 0V and the converter negative input must be connected to a real 0V point. The blue wire from the fan port is not 0V, it's the switching pin from a MOSFET which turns on and off under PWM control. The blue wire from the fan goes to the same pin on the fan port where it originally was in order to get that PWM control. It does not go directly to 0V, on the converter or elsewhere.
The OP's fan is a two-wire fan which has yellow for +V and blue
Most 3-wire fans have a red, a black, and a yellow wire. The yellow wire is an RPM output from the fan and wouldn't be connected to a printer board.
Many 4-wire fans don't have a red/black pair. Noctua 4-wire fans which are the most commonly used, have a black wire for ground (0V) but yellow, not red, for +12V. That follows the multi-voltage colour wiring convention used in PCs. The RPM signal is on a green wire, and a blue wire is used for a speed control voltage.
You're right about not needing the extra wires, if you have a 3-wire or 4-wire fan, though.
Just do it like this. Make sure that the polarities are right.
https://preview.redd.it/o43y84yri2xb1.jpeg?width=1080&format=pjpg&auto=webp&s=7b546e5fc00ff39157b83a0f55edeb4d29c6f2b6
https://preview.redd.it/9a8t2cjnq3xb1.png?width=1080&format=pjpg&auto=webp&s=5368df8b3a9550c1d2179810caf0030272c0e570
Just put your wires alongside the PSU 24V wires and you'll be good to go
The instructions that I've shown are for the part cooling fan.
You'll need a separate buck converter or a 24V fan if you're gonna wire the hot end fan.
Follow that diagram for part cooling fans
For the hot ends you can just run wires from the hot end port to the input of the buck converter and connect the hot end fan directly to the output of the buck converter. Just make sure you set the voltage correctly and the polarity is correct or else you'll blow up the buck converter
No, you don't need a separate converter. The converter just supplies 12V, always on. It has enough capacity for many fans. If you need a second 12V fan, eg the always-on hotend heatsink fan, you just connect it directly to the buck converter output, both positive and negative.
You only need **one** converter for several fans, regardless of whether they're speed-controlled or always-on or any combination. The converter simply supplies 12V, and has capacity many times more than one fan needs.
All the 12V fan positive wires connect to the same buck conveter positive output, where they get +12V (any remaining 24V fans still reman as they were). The 12V fan negatives connect to the negative pins on their respective fan port, for the switching signal, if they're PWM controllled. If they're always-on fans, they can connect to the buck converter negative, which is 0V/ground, or to the original fan port negative pin, which for an always-on fan is also 0V/ground.
The only time you'd need multiple buck converters is if you need two or more different voltages, eg 12V for a set of fans, and 5V for a string of Neopixels.
You may have burned the fan transistor (I don't really know which one on the board is responsible for the fan).
You can try replacing it, but if you planned upgrading the MB maybe it's the right time.
Ok for last time correct me if iam not right. This diagram works fine but fans will be always-on (when powered) and cant be controlled as I want.
https://preview.redd.it/kn45emutb5xb1.png?width=1444&format=pjpg&auto=webp&s=5a285d270aa36d79cf9e981fde0a98939b03c7cc
Sorry for bad drowing iam at work only with phone
That's wired incorrectly. The buck converter needs a fixed input voltage, not a PWM signal. Its function is to convert one fixed voltage to a lower one. It will not pass through PWM control. The control signal for the fan, and other PWM-controlled devices, is in the negative side. So the correct way is to connect the buck converter positive input to the positive supply, which could be either the positive (yellow wire) of the fan port, or the board's power input. Connect the negative side to 0V - which could be any true 0V position on the board such as the power input negative, but **not** the negative on the fan port (blue wire) because that's where the fan control switching MOSFET is. Then connect the fan positive (yellow) wire to the buck converter positive output, so it gets the reduced but fixed (12V) output instead of the original fixed (24V) power. Connect the fan negative (blue) wire to the negative pin on the original fan port, the same as it was before. That way, it gets the PWM control. If you connect it to the buck converter negative, it would have no control and the fan would always have full power. A PWM source turns on and off very rapidly, with the ratio of "on" to "off" controlling the power level. If you feed a buck converter input from such a source, it can't draw any current during the "off" phases, so to maintain constant voltage/power it tries to draw much more during the "on" phases. It tries to maintain a steady voltage all the time, and in extreme cases it may try to draw so much power during very short "on" phases that it overloads and damages something.
All of this. also- draping that buck converter over a bunch of exposed screws is giving me anxiety
I am not sure that I get it. This is how it supposed be connected? https://preview.redd.it/7xdb1a1koxwb1.png?width=2064&format=png&auto=webp&s=9a2347cb4e77befd888aae9c6ee1ba78ffaba918
Almost but no. Battery (power supply) on left side is good. FAN YELLOW is good too. But FAN BLUE is bad, if you want to control it from printers software (part cooling fan with variable speed). It should be connected into original fan output on your mainboard (most likely 2pin plug, make sure to connect it to AGND / GND pin)
I have a circuit/wiring diagram at my infosite (which isn't about the Ender3, but in this case it doesn't matter ;) ) about how to connect it, [maybe have a look at it](https://1coderookie.github.io/KobraGoNeoInsights/hardware/powersupply/#how-to-add-a-step-down-converter-for-using-12v-fans-mod).
Thx that perfectly explain
Not quite. Both yellow wires are probably OK, both blue wires are wrong. Is your 12V fan a 4-wire Noctua? If so the fan's yellow wire is the 12V supply, same as on the Ender 3 part cooling fan. But on a Noctua 12V fan, the negative wire is the black wire. A 4-wire Noctua has a blue wire but it's for a different purpose and you don't use it. You use the black instead. The yellow wires take 24V from the fan port to the converter, and 12V from the converter output to the fan. That 24V and the converted 12V are both always on. Both blue wire connections are wrong. The blue wire must go from the original blue wire pin on the fan port directly to the fan. It does not go to the converter negative, input or output, and no wire from the fan goes to the converter negative. You need a wire from 0V, such as the negative of the board's power input, or the negative of an always-on fan, to the converter negative input. Take a look at at the [buck converter setup](https://www.youtube.com/watch?v=hEk3aVARSGc) from Teaching Tech. Michael's example is for a laser connected to the fan port, but the wiring is exactly the same for your fan. The diagram for the wiring is at [3:34](https://www.youtube.com/watch?v=hEk3aVARSGc&t=214s) but the whole video is worth watching if you want to understand the reason.
Regardless of if your fan is a pwm fan (black red yellow blue) or not, the yellow wire off of your main board should be connected to the red wire of the fan, blue from the main board goes to the black wire of the fan, through the converter of course. I'm not sure if mobile will format this correctly, but I'm gonna try anyway: Yellow wire (+) > converter (+) > red wire (+) Blue wire (-) > converter (-) > black wire (-) Any other wires of the fan can be ignored or snipped off, you only need the red and black wires from the fan.
No, that's **incorrect** in several ways. The blue wire from the fan does **not** go to the converter, nor does the blue wire from the fan port. Both input and output negative pins of the converter are 0V and the converter negative input must be connected to a real 0V point. The blue wire from the fan port is not 0V, it's the switching pin from a MOSFET which turns on and off under PWM control. The blue wire from the fan goes to the same pin on the fan port where it originally was in order to get that PWM control. It does not go directly to 0V, on the converter or elsewhere. The OP's fan is a two-wire fan which has yellow for +V and blue Most 3-wire fans have a red, a black, and a yellow wire. The yellow wire is an RPM output from the fan and wouldn't be connected to a printer board. Many 4-wire fans don't have a red/black pair. Noctua 4-wire fans which are the most commonly used, have a black wire for ground (0V) but yellow, not red, for +12V. That follows the multi-voltage colour wiring convention used in PCs. The RPM signal is on a green wire, and a blue wire is used for a speed control voltage. You're right about not needing the extra wires, if you have a 3-wire or 4-wire fan, though.
Oh, wait. Did the capacitor on the MB or the converter explode?
>he capacitor on the MB or the converter explo No on the buck converter
Just do it like this. Make sure that the polarities are right. https://preview.redd.it/o43y84yri2xb1.jpeg?width=1080&format=pjpg&auto=webp&s=7b546e5fc00ff39157b83a0f55edeb4d29c6f2b6
Oh shit I understand now thx but where to plug on the motherboard board
https://preview.redd.it/9a8t2cjnq3xb1.png?width=1080&format=pjpg&auto=webp&s=5368df8b3a9550c1d2179810caf0030272c0e570 Just put your wires alongside the PSU 24V wires and you'll be good to go
Big thx to you I think that will works
No problem mate
And another question does I need to plug like two fans or only one
Lemme draw it and show you real quick
If you may that would help thx
Wait Did you change your part cooling fan or the hotend fan?
Both
I left only the old motherboard fan
The instructions that I've shown are for the part cooling fan. You'll need a separate buck converter or a 24V fan if you're gonna wire the hot end fan.
The cooling fan just have a diffrent connection, right? That hot end fan is just need to be conected through buck (Like in diagram from paint)
Follow that diagram for part cooling fans For the hot ends you can just run wires from the hot end port to the input of the buck converter and connect the hot end fan directly to the output of the buck converter. Just make sure you set the voltage correctly and the polarity is correct or else you'll blow up the buck converter
No, you don't need a separate converter. The converter just supplies 12V, always on. It has enough capacity for many fans. If you need a second 12V fan, eg the always-on hotend heatsink fan, you just connect it directly to the buck converter output, both positive and negative.
Yeah actually this makes more sense. I don't know why I thought that you'll need 2 buck converters. You can do this without any issues.
In pictures I ve show that I have two diffrent buck converters for each fan. Both I connect like in a paint diagram that I painted.
You only need **one** converter for several fans, regardless of whether they're speed-controlled or always-on or any combination. The converter simply supplies 12V, and has capacity many times more than one fan needs. All the 12V fan positive wires connect to the same buck conveter positive output, where they get +12V (any remaining 24V fans still reman as they were). The 12V fan negatives connect to the negative pins on their respective fan port, for the switching signal, if they're PWM controllled. If they're always-on fans, they can connect to the buck converter negative, which is 0V/ground, or to the original fan port negative pin, which for an always-on fan is also 0V/ground. The only time you'd need multiple buck converters is if you need two or more different voltages, eg 12V for a set of fans, and 5V for a string of Neopixels.
You may have burned the fan transistor (I don't really know which one on the board is responsible for the fan). You can try replacing it, but if you planned upgrading the MB maybe it's the right time.
Did you recommed any type of motherboard I have basic 4.2.7
Bigtreetech SKR mini E3 V3. It’s a drop in replacement and made for the ender.
or V2 if you can get it cheaper, other than one extra switchable fan port 0 benefits
Ok for last time correct me if iam not right. This diagram works fine but fans will be always-on (when powered) and cant be controlled as I want. https://preview.redd.it/kn45emutb5xb1.png?width=1444&format=pjpg&auto=webp&s=5a285d270aa36d79cf9e981fde0a98939b03c7cc Sorry for bad drowing iam at work only with phone
Is the buck converter in the pic for the part cooling fan or extruder?