Powering PWM fans without a PC?

lumencreative · 14 Jan 2023 at 23:21

A bit of an odd one…

I’m trying to build a cooling solution for something at work consisting of 4-6 Noctua industrial 3000rpm PWM fans.

I’ve bought a Molex to 4x 4pin fan splitter and a 12v Molex power supply.

Plugged it all together and nothing. Tested the fan and the Molex to fan splitter in my PC and that worked fine so I think there’s an issue with the power supply, though I’m not sure whether I just bought the wrong thing or whether the power supply is faulty.

The pins on the power supply are correctly laid out, and the power supply can either do 5v or 12v at 2amps. The seller of the power supply suggested the 2amps might be too much for the fans but I don’t know enough to know if that’s true?

So, I wondered if anyone here could advise what I should buy in order to power the fans? Am I better buying a proper ‘external’ fan controller and then finding a way of powering that?

Any advice would be hugely appreciated.

Rroff · 14 Jan 2023 at 23:24

Someone on here used to build a controller PCB for people to drive PWM fans - dunno if they still do - but may find information in those threads on it.

The amperage capability of the supply won't matter as long as it is high enough - the fans will only draw what they need.

lumencreative · 14 Jan 2023 at 23:49

Rroff said:
Someone on here used to build a controller PCB for people to drive PWM fans - dunno if they still do - but may find information in those threads on it.

The amperage capability of the supply won't matter as long as it is high enough - the fans will only draw what they need.

Thanks, will see if I can find the threads.

Yeh, that’s what I thought, that the 2amps would be a ‘max’

Rroff · 15 Jan 2023 at 00:08

lumencreative said:
Thanks, will see if I can find the threads.

Yeh, that’s what I thought, that the 2amps would be a ‘max’

I was trying to find them, but failing so far - was quite awhile back.

EDIT: I was misremembering it was PWM to 3 pin non PWM circuits https://forums.overclockers.co.uk/threads/pwm-to-analog-converter-circuit.18421145/

WJA96 · 15 Jan 2023 at 06:53

It might have been me?

Get a 3-pin fan to use PWM?

Hi all, I recently bought the Zalman fan shown in my signature but it only has a 3 pin header. Is there any way I can get it to use PWM? Thanks :o)

forums.overclockers.co.uk

The fans are looking for a pulse on the PWM pin. No pulse, no spin. PWM works by switching the fan on and off very fast so it appears to run much slower. Because you don’t have a timing chip sending the pulses on the 4th pin the fan won’t spin. Even though it’s getting 12V

Can you not use 3-pin fans as they’ll spin up based on the voltage supplied, not the number of PWM pulses.

If you have to use PWM fans then yes, you’ll need a PWM fan controller with a timing chip to generate the PWM pulses.

Tealc · 15 Jan 2023 at 08:41

You linked to a thread of mine. I did build an external PWM unit but I don't think I went into any detail on how it was built in the threads as that wasn't really the topic.

The circuit itself was built to test the digital PWM to 3 pin fan circuit mentioned above and I built it into a small grey box, mostly. It consisted of a 555 timer IC, and a few other components. I had all the components to hand so was fairly easy for me to make but if you don't have electronics as a bit of a hobby building such a thing might be more difficult.

I've not checked but you can usually pick up little PWM or motor drive PCBs off ebay for a few quid.

lumencreative · 15 Jan 2023 at 10:10

WJA96 said:
It might have been me?

Get a 3-pin fan to use PWM?

Hi all, I recently bought the Zalman fan shown in my signature but it only has a 3 pin header. Is there any way I can get it to use PWM? Thanks :o)

forums.overclockers.co.uk

The fans are looking for a pulse on the PWM pin. No pulse, no spin. PWM works by switching the fan on and off very fast so it appears to run much slower. Because you don’t have a timing chip sending the pulses on the 4th pin the fan won’t spin. Even though it’s getting 12V

Can you not use 3-pin fans as they’ll spin up based on the voltage supplied, not the number of PWM pulses.

If you have to use PWM fans then yes, you’ll need a PWM fan controller with a timing chip to generate the PWM pulses.

So, the fans I bought are NF-A14 industrialPPC-3000PWM’s. I’d read that without the PWM control, they just run at the maximum of 3,000rpm.

When I tested them on my pc, I used the Molex splitter cable I had bought (which just has the 12v wire and the ground wire), and they powered up fine.

I guess the next step would be to buy some form of pwm controller and see if that works.

lumencreative · 15 Jan 2023 at 10:14

Tealc said:
You linked to a thread of mine. I did build an external PWM unit but I don't think I went into any detail on how it was built in the threads as that wasn't really the topic.

The circuit itself was built to test the digital PWM to 3 pin fan circuit mentioned above and I built it into a small grey box, mostly. It consisted of a 555 timer IC, and a few other components. I had all the components to hand so was fairly easy for me to make but if you don't have electronics as a bit of a hobby building such a thing might be more difficult.

I've not checked but you can usually pick up little PWM or motor drive PCBs off ebay for a few quid.

Had a quick look online and thinking of getting the Akasa FC.Six. It’s not technically ‘external’ but says it can be powered by a Molex.

There are cheaper alternatives available but Akasa is a brand I know of.

I’ll also order a 3 pin fan as well just to test it out in comparison.

lsg1r · 15 Jan 2023 at 13:23

@lumencreative

I was going to suggest one of those dial/knob controllers that went in a drive bay as an 'inbetween'...

Then I though I'm using the noctua na-fc1 for some 60mm fans in my o11 evo.. it's pretty solid for such a tiny device and can probably tucked away easier than the 3.5/5.25inch options I was originally thinking of... it should do the same job, it's just smaller.

NA-FC1

The NA-FC1 is a compact, highly flexible controller for 4-pin PWM fans that can both work on its own for manual speed reduction and also work in tandem with the automatic motherboard fan control. By adjusting the NA-FC1’s speed control dial, users can either manually set a PWM duty cycle from 0...

noctua.at

BUDFORCE · 15 Jan 2023 at 21:01

Assuming you don't have a multimeter?

They are really useful and pretty cheap (you don't need a posh one unless you are component testing) but you could test to see if the power supply is outputting 12v easily with that.

clone · 16 Jan 2023 at 08:12

Buy a cheap psu and fan controller.

lumencreative · 16 Jan 2023 at 11:06

clone said:
Buy a cheap psu and fan controller.

Problem with a psu is it needs some way of powering it on. I know you can jumper wire it to power it on but that’s not really a viable option long term.

I’ve got an Akasa FC.SIX arriving today so will see if that works, otherwise will be buying a multimeter (may get one anyway to be honest).

@lsg1r I did look at that Noctua controller but the reviews I read suggested it needed the pwm signal from the motherboard to control the fans. Not sure how true that is but that’s why I went with the Akasa as a first option.

lsg1r · 16 Jan 2023 at 12:02

lumencreative said:
@lsg1r I did look at that Noctua controller but the reviews I read suggested it needed the pwm signal from the motherboard to control the fans. Not sure how true that is but that’s why I went with the Akasa as a first option.

Mines not connected to the motherboard at all (no fan sockets left...), the little 'dial' adjusts the speed up and down to my preferred rpm and then it just sits there at that speed.

If you plug it into the motherboard pwm it acts like a 'limiter' on the fan speeds, it will still go up and down but it will be reduced (think of those inline 12v to 7v cables but with more adjustment)... wouldn't matter in your case though.

You say about the psu on/off issue, you can actually get some power button based jumpers now, from around £5 (google pc psu jump start button), but I'd say you could probably do your own based on everything else you're doing lol.

lumencreative · 16 Jan 2023 at 16:16

Just an update, Akasa controller arrived today and works fine with the Molex power supply I’d bought.

Blimey these 3,000rpm fans are fast…now wondering whether they’re too fast haha but they’re only £2 more than the non ‘industrial ones’ at 1,500rpm and they’re the same price as the 2,000rpm industrial ones, though the 2,000rpm ones are 10db quieter.

Decisions decisions haha.

alphaomega16 · 4 Aug 2024 at 19:21

lumencreative said:
Just an update, Akasa controller arrived today and works fine with the Molex power supply I’d bought.

Blimey these 3,000rpm fans are fast…now wondering whether they’re too fast haha but they’re only £2 more than the non ‘industrial ones’ at 1,500rpm and they’re the same price as the 2,000rpm industrial ones, though the 2,000rpm ones are 10db quieter.

Decisions decisions haha.

Sorry to bump an old thread but been googling, want some kind of fan controller powered by 3pin plug myself, how are you getting on with what you done also what was it specifically you purchased if it worked out well?