How to power a 4-pin CPU fan? : hardware@lemmy.ml

How to power a 4-pin CPU fan? (programming.dev)

submitted 9 months ago by emotional_soup_88@programming.dev to c/hardware@lemmy.ml

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I disassembled an AMD CPU Wraith Cooler, meaning, I took the fan off of the heatsink, because I want to attach the fan on top of a Raspberry Pi that I'm using as a router. The Pi runs quite hot because it transmits several hundred megabytes per second, non stop, and I want to give it some cooling. (It already has its own heatsinks on its various chips inside the chassi and I don't want to use the little shitty Okdo fan, because it's loud.)

Is there any smart solution to how I could power this 4-pin fan? It needs 12V DC.

This is the Pi with its chassi.

And I'm considering something barbaric like this.

~~Are there perhaps conveniently positioned GPIO pins on the Pi that the 4-pin connector could just slide on to and just work?~~ Never mind this. The Pi 4 that I'm using can only output 5V:

Or would I need to cut off the 4-pin connector to expose the individual wires and attach them to a 12V DC adapter?

Or any other genuis solutions? :)

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[–] fuzzy_tinker@lemmy.world 7 points 9 months ago (5 children)

1st, do not power the fan from the pi if possible to avoid any underpower headaches. It should be fine.

Your best bet is to just power it at 5v using a standard USB wall wart and a sacrificial USB cable (old 2.0 ones work best). Strip the USB cable and expose the positive and negative wires and hook them up to the positive and negative fan pins (identify these using a 4pin fan header diagram). You can either try just shoving the tips of the USB cable into the fan header using electrical tape as a quick bodge, or cut and strip the fan cables and twist them together.

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[–] emotional_soup_88@programming.dev [S] 2 points 9 months ago (4 children)

Gotcha! Thanks for the directions! Any reason why I shouldn't power it with 12V, since it says 12 on the fan...?

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[–] stevestevesteve@lemmy.world 3 points 9 months ago

You should indeed power it with 12v

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[–] Romkslrqusz@lemmy.zip 3 points 9 months ago* (2 children)

Assuming the supply can saturate the current the fan will use, at 12V it’ll be running at full speed. That’s probably pretty loud. Give it 5V, it’ll run slower and quieter.

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[–] emotional_soup_88@programming.dev [S] 1 point 9 months ago (1 child)

I just found a "noise reduction cable" from Noctua. It ads 51 Ohms. I have no idea how to calculate what the new voltage would be on a 12V 2A DC power supply ( https://www.noctua.at/en/products/nv-ps1/specifications ), but Noctua's website says that the cable lowers fan speeds, so I'll give it a try.

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[–] Romkslrqusz@lemmy.zip 3 points 9 months ago

Yeah, it’s just an inline resistor

A potentiometer is a resistor that you adjust using a dial. If you want control, you may want to get a PWM fan control module. There’s the Noctua NA-FC1 https://www.noctua.at/en/products/na-fc1 but that’s pretty much just a fancy expensive version, you can find the same concept for as little as $1-2 USD

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[–] fuckwit_mcbumcrumble@lemmy.dbzer0.com 7 points 9 months ago (1 child)

You can buy usb to 12v fan adapters for like $8 on Amazon.

But for a pi you don't need that fan to run at full speed, just the 5V of USB or that header + any sort of a heatsink on the CPU will be plenty.

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[–] emotional_soup_88@programming.dev [S] 2 points 9 months ago

5V seems to the consensus, so I'll go in that direction. But I do want to keep the chassi on, so I think I'll go with a 5V USB.

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[–] lime@feddit.nu 5 points 9 months ago* (last edited 9 months ago) (3 children)

fourth pin is an output i think.

https://glkinst.com/cables/cable_pics/4_Wire_PWM_Spec.pdf

if you bypass it you don't get a signal from the rotation speed sensor and the fan should run at 100% given 12v.

easiest solution is probably one of those 12v inverters for cars but that seems overkill. 5v fans are most likely cheaper.

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[–] emotional_soup_88@programming.dev [S] 2 points 9 months ago (2 children)

Right! I have no reason for it to run art full speed on a Pi anyway. I'm leaning towards buying a 5V USB adapter.

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[–] lime@feddit.nu 3 points 9 months ago (1 child)

does it work at all on 5v?

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[–] emotional_soup_88@programming.dev [S] 2 points 9 months ago

I guess I have to try. It either stalls and doesn't turn at all, or I get a comfortable breeze.

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[–] anamethatisnt@sopuli.xyz 4 points 9 months ago (1 child)

If you decide you wanna go the easy route there are quiet 5V fans out there
https://www.noctua.at/en/products/nf-f12-5v-pwm

pi-noctua-pwm
Controls a 4-pin (PWM) 5V Noctua fan using a Raspberry Pi 5's GPIO pins. The fan speed is automatically adjusted based on the temperature readings from an NVMe drive, making it ideal for cooling solutions like the Pimoroni NVMe Base.

https://github.com/mplogas/pi-noctua-pwm

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[–] emotional_soup_88@programming.dev [S] 3 points 9 months ago

Thanks! That lead me to discover this: https://www.noctua.at/en/products/nv-ps1/specifications Which I guess would have the fan blast away at full speed, but maybe I could force a potentiometer in between somewhere somehow...?

Or, I just go the easy way, as you said. I just hate to know that the Wraith is sitting in my closet, unused... XD

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[–] AlphaOmega@lemmy.world 3 points 9 months ago* (1 child)

A good external desk/box/tower fan might be an easier solution

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[–] emotional_soup_88@programming.dev [S] 3 points 9 months ago

Thanks, I thought of that too, and I'll go with that if this doesn't work. I just didn't want this little Wraith lying around unused and the size fits so well on the Pi 😄

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[–] vk6flab@lemmy.radio 3 points 9 months ago (1 child)

https://allpinouts.org/pinouts/connectors/motherboards/motherboard-cpu-4-pin-fan/

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[–] emotional_soup_88@programming.dev [S] 2 points 9 months ago

Bookmarked!

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[–] meathorse@lemmy.world 3 points 9 months ago* (2 children)

12v fans will typically run fine, albeit much slower at 5v. This was a favorite trick many moons ago to reduce fan noise in desktops before quiet fans became mainstream. The main watch out is that the fan doesn't stall at startup and fail to spin completely.

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[–] emotional_soup_88@programming.dev [S] 1 point 9 months ago

Right, so less voltage, less speed. Couldn't I "shove" a potentiometer in between and give it around 7,5V or whatever gives the best noise to temp results?

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[–] Chronographs@lemmy.zip 1 point 9 months ago

That would obviously work with older dc fans but modern ones use pwm which iirc is a constant voltage just pulsed to varying degrees (thus pulse width modulation)

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[–] Orygin@sh.itjust.works 3 points 9 months ago (2 children)

You can use a transistor to pwm the 12v input to the fan. I used IRLZ44n to this effect since they work ok at logic level. There are better transistors but the principle is the same

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[–] emotional_soup_88@programming.dev [S] 3 points 9 months ago* (last edited 9 months ago) (1 child)

Nice! I was just going to ask if I should add in a potentiometer to regulate the fan speed. But you say it should be a transistor? I'm a complete noob at hardware, so please excuse any inaccurate lingo. 😅

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[–] Orygin@sh.itjust.works 2 points 9 months ago*

The pot is if you want to control the speed manually. The transistor if you want to control it from the pi (from the temperature for example).

If you want a potentiometer, there are two ways I think :
Have the potentiometer plugged to the pi ADC input, and in software regulate the pwm output to the transistor based on the signal coming from the pot.
Another way is to have the potentiometer in series with the fan and only control it from the pot. I've never built any circuit like this so there may be consideration to be put into the max current the pot can handle, but I guess for a small fan it could be okay.
In both cases you'll need a 12v source. Either a 12v power supply, or a DC step up from 5v (from the 5v power supply (maybe the same as the pi), not from a pin on the raspberry as it can't draw much current). In both cases, the grounds should be tied together so they all see the same voltage in reference to ground.

I can help you further if you want, but don't hesitate to ask a LLM for it as they can be quite good now for such circuits, and can in theory explain concepts you don't yet understand.

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[–] exu@feditown.com 3 points 9 months ago (1 child)

I think PWM fans need 12V all the time. Maybe you have a cheap 3-pin fan, then you can just give it 5V. It'll run slower, but you probably don't need full power.

You could get a cheap boost convert to up 5V to 12V if you want the Pi to power it.

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[–] emotional_soup_88@programming.dev [S] 1 point 9 months ago

I had no idea the Pi's output could be boosted. Sweet!

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[–] krolden@lemmy.ml 3 points 9 months ago

https://www.amazon.com/LINKUP-4-Pin-Sleeved-Power-Adapter/dp/B07J2SRVNM