Multi-channel fan controller for several PWM/Non-PWM fans Vs a decent MB?

If one or some could help me determine the best direction to go here I'd be most appreciative.

jalyst said:

I'm just a little stunned though...
That there aren't any pre-built fan controllers with several channels integrated of the kind Bing demonstrated.
So that one can manage several PWM fans at once, & get speed feedback etc.
Ideally one that can handle a mixture of PWM & non-PWM (4-wire or 3-wire) capable fans if needed.
Surely there's something on this planet that one can buy? Ideally one that needn't be mounted into a 3.5" or 5.25" bay!

Click to expand...

Actually there seems to be a few multi-channel controllers now which do 3-pin, but also have at-least one channel for PWM fans.
Nothing I've seen that avoids using a bay though unfortunately
So no need for the self-build route, but I do get that you guys like doing this stuff for fun!

LennyRhys said:

When my San Ace fans arrive, and when I decide exactly what fans I'm going to put in my case and where, I'll be building a "proper" fan control unit with designated channels for each fan. There will be only one pwm circuit because I'll only need one San Ace fan (for the CPU cooler) and the rest will either be simple on/off switches or linear voltage controllers courtesy of bing.

Click to expand...

Do you realise there's a few pre-built controllers out there (some that aren't bad quality) that can do this now?

jalyst said:

So like you I will probably have a mixture of PWM and non-PWM fans.
Is there not anything pre-built to accommodate for this?!
If I can get away with my motherboard accommodating all this without any massive caveats than I'd greatly prefer that.

Click to expand...

So upon closer inspection there seems to be some pre-built options, BUT ALSO, if I understand correctly...
Martinm210 described a circuit one can use in conjunction with their MB, so that one can use their MB to control PWM & non-PWM fans, even high wattage ones!
My mobo may actually have just enough fan-headers (2x 3-pin and 2x 4-pin), with enough juice on the 3-pins for multiple AP-14/15's*.
If anyone knows what he may be talking about, plz can you let me know!?

*update*
I misunderstood him, anyway it's easy enough to connect the the +/- wires of the higher draw PWM fans directly to the PSU.
Should I decide to go the MB route initially....

LennyRhys said:

I'm not sure. If the scythe GT fans were PWM I'd consider it a bit pointless, seeing that they are already very quiet at their rated speed, nullifying (imho) the requirement for speed control...moreover they are available in different speeds anyway.

Click to expand...

You're prolly right, if I check their spec. page I should be able to verify whether they're PWM or not.
Even if they're not, I'll have at least one PWM >3000RPM fan, so it'll need to be accommodated somehow.

The best course of action is to choose what you want most from the fans - versatility, performance, or silence. Very few fans offer all three (which is where the controller comes in) and your best bet is to go for a compromise.

Click to expand...

This seems to be changing with the release of these higher-end Nidec 25mm fans, which may well offer the trifecta!?

*UPDATE, it seems my MB only has the following:
1x CPU fan-header (PWM)
1x chasis fan-header_1 (PWM)
1x chasis fan-header_2 (3-pin)
1x Power fan-header (3-pin)
I was hoping there'd be more fan headers in-total, but at least there's my requisite minimum of 2 PWM headers.

[proposed layout]
I guess I could have the 2x AP-15's (maybe 4x) for the Rad. coming-off the CPU fan-header? (may not be possible if AP-15 aren't PWM)
Two of the three (1 will be donated) >3000RPM PWM GT's I'm importing could sit on chasis fan-header_1?
That's assuming the mod to ones MB martin was talking about is possible, otherwise their current draw would be too high right?
If it is possible, then eventually they could even sit on the CPU fan-header, replacing the 2->4 AP-15's.

For the remaining two 3-pin headers I'll sit 1->3 (total of no more than 6, probably less) AP-14's?
If the CPU fan-header can't take the AP-15's, I may have as many as 5 (3x AP-14 & 2x AP-15) fans coming-off each of these headers!
This isn't ideal, aside from the fact that I may not be able to adjust fan speed from these headers, independent control/monitoring of these two groups makes sense.
Plus I'm not sure if these two headers could handle that many fans (of that draw) on them anyway...
[/proposed layout]

Are 3-pin headers essentially linear voltage controllers (i.e. rheostat/bus) that can run 3-pin fans at 12v or less?
Or can they only run non-PWM fans at their rated top (12v) speed?
Can anyone advise if this configuration will be possible with some "tweaks", or is a dedicated controller looking necessary?

*EDIT* Perhaps a better proposed layout is:

[proposed layout]
2x >3000RPM PWM GT's (model YTBD, prolly the 5400) each sitting on their own PWM header, with their +/- going direct to the PSU?
Then I could put the up-to-4x AP-15's on one of the 3-pin headers, & the up-to-6x AP-14's on the remaining 3-pin header?
[/proposed layout]

Would the 3-pin headers take the load, or would some of the GT's on them have to be rigged direct to the PSU?
Does this all sound too clumsy, is a dedicated controller looking to be imperative IYO?

I'd rather not have something that uses a bay, but would still like RPM/voltage feedback & at least auto-control if possible.

AP 15/14's etc are NOT PWM. 3 Pin. So you need the standard Mosfet etc on the mobo or controller to handle the startup current of each.

Yes, they are directly controlled by the raw voltage applied to the fan, they have no PWM hardware on the fan. And they do undervolt well. So for voltage control they have to be connected to the voltage control device, branching the power wires to the PSU will ensure 100% RPM all the time, no matter what you want to do with the RPM sensing wire.

I know the GT15's are about .3 amps on startup. Adjust accordingly for the 14's.

Mobos have a higher amp CPU connector, some mobos are 3/4 pin and allow either type to be used. Most are PWM 4 pin I 'think' tho. 1 Amp is the common accepted CPU header max allowed, the others? .5 Amp.

Think of this.... Using the mobo and all the availible fan headers on the mobo makes a absolute mess of wiring.

Get a solid quality fan controller, make do with one less slot.

1-6 GT14s spread between two mobo headers? Nope....

Sorry I didn't read every bit of the post you made, but maybe this will help.

I think Conumdrum answered most of your questions.

Perhaps you can answer a question for us - why do you want control and RPM feedback of so many fans, motherboard or otherwise?

I'm building my controller because I want my system to tick all the air cooling boxes - silence, efficiency, and raw performance. To claim all three with the same fans simply isn't possible without a controller. Silent cooling may be efficient but cannot provide raw performance; efficient cooling may be silent and may perform well but excels at neither; and performance cooling is highly efficient but never silent.

As it stands, my silent rig is composed entirely of low speed fans; for efficient cooling (when stress testing etc) I have to swap out the CPU fan for something more powerful; and for raw performance during benching I have to set up several fans to cool the chipset, VRM, memory etc. in addition to swapping out the CPU fan again.

Apologies for the ridiculously delayed response, super busy lately, want to get this sorted in the next 24hrs.
Thanks for confirming the AP-14/15's aren't PWM, and do under-volt well!

Conumdrum said:

AP 15/14's etc are NOT PWM. 3 Pin.
So you need the standard Mosfet etc on the mobo or controller to handle the startup current of each. Yes, they are directly controlled by the raw voltage applied to the fan, they have no PWM hardware on the fan. And they do undervolt well. So for voltage control they have to be connected to the voltage control device, branching the power wires to the PSU will ensure 100% RPM all the time, no matter what you want to do with the RPM sensing wire.

I know the GT15's are about .3 amps on startup. Adjust accordingly for the 14's. Mobos have a higher amp CPU connector, some mobos are 3/4 pin and allow either type to be used. Most are PWM 4 pin I 'think' tho. 1 Amp is the common accepted CPU header max allowed, the others? .5 Amp.

Click to expand...

According to Scythe's global site, peak draw for AP-15 is 0.083, & AP-14 is 0.049.
YTD the max. draw for each of my headers, but assuming you're right & the CPU_Fan PWM header is 1amp & the other 3 are 0.5...

Then that means one of the 3-pin headers will comfortably support up to 4x AP-15's at their top speed (0.332).
And the 2nd 3-pin will comfortably support up to 6x AP-14 at their top rated speed (0.294).

Think of this.... Using the mobo and all the availible fan headers on the mobo makes a absolute mess of wiring.
Get a solid quality fan controller, make do with one less slot.
1-6 GT14s spread between two mobo headers? Nope....
Sorry I didn't read every bit of the post you made, but maybe this will help.

Click to expand...

Actually it's 2-4 AP-15's for one header & 2-6 AP-14's for the other, so as many as 10x AP15/14's between the 2x 3-pin headers.
Then we've got up to 2x PWM fans >3000RPM (prolly the 5400's) sitting on the 2x PWM headers. So yeah, prolly quite a mess!

I probably will get a dedicated controller in the coming months.
I just want to make sure it's do-able with my MB only in the meantime.

It certainly did help, and was most appreciated!

Again, apologies for the ridiculously delayed response, super busy lately! :|

LennyRhys said:

I think Conumdrum answered most of your questions.

Click to expand...

I think you missed some Qns directed at you if you've got a minute to address them?

I've since identified at least one flaw with the multi-channel PWM/LVC controllers I've seen so far:
They don't interface with our MB/BIOS/EFI & adjust LV/PWM of their channels independently, based on temp readings passed from the MB.
Plus RPM data of each fan can't be passed back to the MB....

Such a set-up would be close to 'Fan-control Nirvana' IMO....
This 'kinda' comes close, cept that it has manual control & hence requires a bay, which I don't need.
And the input 4-pin molex connection is only suited for 60-80W, so even running 2-ch at full capacity could get dangerous.

Perhaps you can answer a question for us - why do you want control and RPM feedback of so many fans, motherboard or otherwise?

Click to expand...

If it's do-able, why not?!

I'm building my controller because I want my system to tick all the air cooling boxes - silence, efficiency, and raw performance. To claim all three with the same fans simply isn't possible without a controller. Silent cooling may be efficient but cannot provide raw performance; efficient cooling may be silent and may perform well but excels at neither; and performance cooling is highly efficient but never silent.

Click to expand...

This is precisely what I'm aiming for, but in a pre-built controller device, if not possible via MB.

As it stands, my silent rig is composed entirely of low speed fans; for efficient cooling (when stress testing etc) I have to swap out the CPU fan for something more powerful; and for raw performance during benching I have to set up several fans to cool the chipset, VRM, memory etc. in addition to swapping out the CPU fan again.

Click to expand...

I don't envision needing to swap-out the chassis fans very often...
But I may decide to get more heavily into OC, & hence need some stronger fans around the chassis to cool chipset/vrm/mem etc.
And I may eventually replace the AP-15's on my Rad with 2x 5400RPM GT, if testing of 1x goes well.

Primarily the build isn't a 'hard-core' OC/gaming machine....
It's primary utility is HTPC/PVR (BE+FE), & to some extent initially, a NAS.
But I will play with mild OC's, & eventually may even want to go more 'hard-core'.
The majority of the time though it'll run at stock, or even slightly UC.

I have searched high and low for such a controller, but there is no such beast. Which is precisely why I built my own. It is not cheap however it is only necessary if you wish to run 2500+ rpm fans. Pwm is the best method, however it is also the most expensive and since it is relatively new to the cooling world, there are no pre-existing controllers. I had posted to get an interest check, but there were no bites, so I decided against producing them. Initially your looking at a 50-100 dollar cost for a "not so pretty" controller. And its pretty much beta, so you take what you get, which is pretty expensive. The bright side is that one should be capable of running multiple fans. I can also make it pretty small. Again, price and looks make it a not so desirable device, not to mention temp controlled is not even in the equation. this should be considered extreme cooling based off the price alone.

jalyst said:

But I may decide to get more heavily into OC, & hence need some stronger fans around the chassis to cool chipset/vrm/mem etc.

Click to expand...

Chipset/vrm/mem don't need active cooling for overclocking, unless you want to break some hardware records on hwbot; and chassis fans in that area are usually extracting air, not actively cooling. I built my controller for benching, and when I say benching I mean voltages of 1.65v on the CPU and QPI (forget PWM fans and copper heatsinks...most people using these voltages use dry ice or liquid nitrogen LOL).

Why not consider passively cooling your system, especially if it is an HTPC and it's going to be underclocked most of the time? I tried passively cooling my CPU @ 4GHz when I got the copper TRUE, and I was amazed at how well it held up...



Just a thought.

For the 2x 5400RPM 120x25mm fans I'm considering.*
The options -as I see them- that I have are:

(1)
Buy 2x D1225C12BBAP-31 & pair 2x with a fan controller that has 2x high-freq. PWM channels**.
Or does plugging these 2x non-PWM (3-pin) fans into 2x high-freq. PWM channels, not turn them into PWM capable fans?

If it doesn't (actually I don't think it does), then I could still plug them into the controller's 3-pin channels instead.
Granted I'd be using linear voltage control instead of PWM, but I'd still retain all the functionality of option (2) right?
e.g. RPM/voltage feedback, and speed control, just not the same power efficiency...

(2)
Buy 2x D1225C12BBZP-00 & feed +/- wires of 2x directly to the PSU (not sure how best to manage that), & then connect their PWM/RPM wires to the 2x PWM fan-headers on my mobo?

I haven't done the math but I suspect option (2) will be pricier than option (1), despite the latter not needing a discrete controller.
This is because the Nidec 5400RPM 25mm PWM fans, have to be imported at much greater expense than their Scythe equivalents.
This makes option (1) even more attractive, because not only will it be cheaper, but I'd also own a muilti-channel PWM/Non-PWM fan controller!
Admittedly though I haven't done the math, so it may not work-out to be cheaper.

Finally, is my MB's PWM likely to be high-frequency PWM?
How do I determine whether decent quality PWM has been implemented?
For instance this user's MB isn't able to regulate his fan down to 1000RPM via it's PWM header.
The lowest it can go is 2400, despite the fan being capable of 1000RPM.

*assuming that's the highest RPM 25mm fan from Nidec now?
**Doesn't look like Lamptron make one, but I've seen a few already with at least 1x PWM channel.
Not sure if they do 30watts/channel like the FC5, & not sure if there's any that don't have to be placed in a bay.
And not sure if any of them actually make 'decent' PWM channels!

1) Plugging 3 pin fans to 4 pin PWM channels does not turn them into PWM fans... I wish it were that simple.

2) This would be your best option. PWM fans drawing power straight from the PSU and being controlled by the PWM signal from the MoBo header. You may be able to get away with running multiple fans per header provided the PWM signal doesn't degrade too much over the parallel circuits and that you only connect the RPM wire from one of the fans into the MoBo.

I haven't looked at the prices on the fans, but those 150CFM Nidecs from option 1 should run about $40 a piece and the PWM versions would probably be even more expensive... So in this particular case "cheap" would be a relative term.

* From what I've found on the Nidec site; the 5400rpm is the top dog in that category.

** Zalman makes one: ZM-MFC2 --> Only one PWM channel, and it's only rated at 0.7Amps so no high powered fans with it or it will make pretty blue smoke quicker than you can say Zalman.

** The Sumbeam Rheosmart 6 takes PWM signal from a MoBo header and adjusts the speed of regular 3pin fans based on that. It does have a rating of 30W per channel. So in this case you would go with the fans from option 1 and this controller.

xXSebaSXx said:

1) Plugging 3 pin fans to 4 pin PWM channels does not turn them into PWM fans... I wish it were that simple.

Click to expand...

As I suspected, thanks!

What of this?
If it doesn't (actually I don't think it does), then I could still plug them into the controller's 3-pin channels instead.
Granted I'd be using linear voltage control instead of PWM, but I'd still retain all the functionality of option (2) right?
e.g. RPM/voltage feedback, and speed control, just not the same power efficiency....

2) This would be your best option. PWM fans drawing power straight from the PSU and being controlled by the PWM signal from the MoBo header.

Click to expand...

Yeah I'm inclined to agree....
So long as 2x PWM 5400RPM imported from Japan (YTD there's def. none in Europe/US), isn't much more $ than 2x non-PWM + controller from a US retailer.
As I'd prefer to rely on MB only initially, so I can continue to search for a controller that's sophisticated enough for my requirements previously outlined.
Guess it's time to just get the calculator out!

You may be able to get away with running multiple fans per header provided the PWM signal doesn't degrade too much over the parallel circuits and that you only connect the RPM wire from one of the fans into the MoBo.

Click to expand...

Not necessary, I'll only have 2x PWM fans....
I have 2x PWM headers, so RPM/PWM for each fan, can be run to it's own header.

* From what I've found on the Nidec site; the 5400rpm is the top dog in that category.

Click to expand...

Thanks for confirming, I will prolly do a final check myself at some stage.
I hate the layout of the site, very weird....

**Zalman makes one: ZM-MFC2 --> Only one PWM channel, and it's only rated at 0.7Amps so no high powered fans with it or it will make pretty blue smoke quicker than you can say Zalman.

Click to expand...

Nah no good, there's got to be much better options out here, but thanks for the suggestion!

**The Sumbeam Rheosmart 6 takes PWM signal from a MoBo header and adjusts the speed of regular 3pin fans based on that. It does have a rating of 30W per channel. So in this case you would go with the fans from option 1 and this controller.

Click to expand...

Yeah I read about this in another thread, not a huge fan of the concept.
If I get a discrete controller, I'd like it to be able to interface with the BIOS/EFI or OS, but not at the expense of having only one PWM channel for all it's fans.
Plus I don't really NEED manual control, especially when it results in a bay being consumed.
Finally the input 4-pin molex connection is only suited for 60-80W...
So even only running 2-ch at full capacity with the 5400RPM fans could get dangerous!

What of this?
Finally, is my MB's PWM likely to be high-frequency PWM?
How do I determine whether decent quality PWM has been implemented?
For instance this user's MB isn't able to regulate his fan down to 1000RPM via it's PWM header.
The lowest it can go is 2400, despite the fan being capable of 1000RPM.

Thanks for adding your thoughts, it really is appreciated!

jalyst said:

What of this?
If it doesn't (actually I don't think it does), then I could still plug them into the controller's 3-pin channels instead.
Granted I'd be using linear voltage control instead of PWM, but I'd still retain all the functionality of option (2) right?
e.g. RPM/voltage feedback, and speed control, just not the same power efficiency....

Click to expand...

To be honest I would not risk plugging high powered fans to the MoBo header for anything other than the PWM signal and RPM sensor... I would not dare draw the power those things want from the MoBo header from fear of frying the damn thing. I think that with fans rated at anything higher than 1A (12W) you should be looking at powering them from the PSU... Remember that it's not just the 12W, those things will draw almost double their rated amperage at startup and that spike might be enough to send your MoBo crying to a dark corner.

jalyst said:

Yeah I'm inclined to agree....
So long as 2x PWM 5400RPM imported from Japan (YTD there's def. none in Europe/US), isn't much more $ than 2x non-PWM + controller from a US retailer.
As I'd prefer to rely on MB only initially, so I can continue to search for a controller that's sophisticated enough for my requirements previously outlined.
Guess it's time to just get the calculator out!

Click to expand...

You found the non PWM from a US retailer? And they have them in stock?

If you want to go all out; take a look at these: G1238B12BBZP-00
They are double the price of your GT 5400 rpm... But you get 261CFM and the highest static pressure that one can find on a 38mm thick fan. The drawback to these is that they work on their own PWM frequency (500Hz to 5KHz) whereas MoBos usually work on the 16KHz or 25KHz frequency; so for that fan you are definitely looking at building your own custom solution.

jalyst said:

Not necessary, I'll only have 2x PWM fans....
I have 2x PWM headers, so RPM/PWM for each fan, can be run to it's own header.

Click to expand...

That would be perfect for you then.

jalyst said:

What of this?
Finally, is my MB's PWM likely to be high-frequency PWM?
How do I determine whether decent quality PWM has been implemented?

Click to expand...

You could contact support for the MoBo manufacturer and ask them what PWM frequency they run their MoBos at. The general consensus is that PWM frequencies are either 16KHz or 25KHz.

jalyst said:

For instance this user's MB isn't able to regulate his fan down to 1000RPM via it's PWM header.
The lowest it can go is 2400, despite the fan being capable of 1000RPM.

Click to expand...

That could be a case of that particular fan model being calibrated to run at 16KHz and the MoBo header running at 25KHz... In that case, the lowest duty cycle from the MoBo header would not be low enough to make the fan slow down all the way down to 1000rpm.

For instance this user's MB isn't able to regulate his fan down to 1000RPM via it's PWM header.
The lowest it can go is 2400, despite the fan being capable of 1000RPM.


with PWM the fan itself is designed to not drop below 20% speed, that is why he isnt getting full control of it. the intel spec stuff that the fan makers are following somewhat, says that.
that way it always starts up, even if the fan controller croaks, and they do and have.

which is sort of strange, because one of the best purposes for PWM is keeping the voltage the SAME, and sending it in chopped up to the motor. by doing that many motors will start way slower than they will with voltage control.

if all you want is to have the RPM on the board, the power from the PSU and to cool them out when desired, a "SPDT Center off switch" and 2 resisters will easily give each fan 3 speeds, quiet , normal and blow me away. its cheap easy leaves most stuff the same, and i only ever need 3 speeds anyway. but i would have to tune those speeds carefully.

that would be basically ignoring the PWM and just voltage controlling, or tuning it even further so that any PWM could operate still at the resisted voltage/power.

then you put the switches on a faceplate where there is shared space because a hard drive doesnt need all that space, and it stupid easy simple, nothing can burn out over time, and it gets it done. Old School Fool, but hey when everything else dies of complexity , it will still work.

Psycogeec said:

with PWM the fan itself is designed to not drop below 20% speed, that is why he isnt getting full control of it. the intel spec stuff that the fan makers are following somewhat, says that.
that way it always starts up, even if the fan controller croaks, and they do and have.

Click to expand...

That may be the case for what the motherboard headers can output, but you can still controll PWM fans in the full range 0% to 100% duty cycle.

Qoute below from this post...Here

LennyRhys said:

Heh bing - I had planned to sell three of the fans because I'll only need one, but now I want to keep them beecause they ROCK

When I have time I'll wire them up so that I have four of them hooked to the same controller; the biggest problem is power draw - 16 amps with all fans at full speed so I have to carefully consider how to configure the 12v lines from the power supply. I suppose I could use my PCI-E 8-pin connectors.

For now, here's a quick video - my ears feel like they are bleeding; that whining/screaming noise is REALLY annoying lol, and I thought the Delta was lound until I heard this fan

Click to expand...

The controller LennyRhys built is a 2% to 98% controller, but on thread you can find the schematics for a 0% to 100% controller as well.

xXSebaSXx said:

That may be the case for what the motherboard headers can output, but you can still controll PWM fans in the full range 0% to 100% duty cycle.

.

Click to expand...

right i should have said, for the stuff that follows the specs, and i really dont know if it is the fan or the control, what i thought i read was its the way that intel expected the fan to be built.

we can PWM any fan like any other motor, bypassing the fans own PWM stuff Just by pulling that control off, and voltage control any PWM fan, or non-pwm fan.
so there isnt any restrictions that gets in the way of doing anything you want. on the fan side, including both, for either if done correctally.

I don't know that it has to do with following specs... PWM fans are normally in the 16KHz or 25KHz frequencies... Motherboard manufacturers generally make their PWM controllers work on the 25KHz frequency (most common one)... The reason some fans will not slow down below 10% or 20% on certain motherboards is not due to the fact that they are not to spec, but to the fact that the motherboard manufacturers configure the headers to go to no less than said 10% or 20% duty cycle.

As for controlling PWM fans bypassing the PWM circuitry... True; you can do it by just voltage regulation... But why would you spend the extra money on PWM fans if you're just going to use them as regular 3-pin fans?

Another drawback of this approach is the fact that we are talking about high powered fans here... the weakest fan mentioned on here pulls 1.14 amps at 12 volts... that makes this fan a ~14W fan... The most powerful fan on this thread draws nearly 50W or power.... My guess is that if you go with resistors; you're going to need some mighty big ones so that they don't just burn off... and using those still leaves us with the fact that all that voltage that they are not sending to the fan is converted to heat that you're goint to be putting into the case... It kind of defeats the purpose of high powered fans if you're just going to be moving hot air around.

Keep in mind that most mobo headers are only rated to 1a anyways...and resistors don't generate that much heat. The amount of heat generated = total wattage the fan can use (at 12v) - the current wattage used by the fan...so you really won't be dumping more than 50w into open air across a large surface area that doesn't need to be cooled....it's about like a northbridge.

xXSebaSXx said:

I don't know that it has to do with following specs... PWM fans are normally in the 16KHz or 25KHz frequencies... Motherboard manufacturers generally make their PWM controllers work on the 25KHz frequency (most common one)... The reason some fans will not slow down below 10% or 20% on certain motherboards is not due to the fact that they are not to spec, but to the fact that the motherboard manufacturers configure the headers to go to no less than said 10% or 20% duty cycle. .

Click to expand...

see what they have done by making this complicated, it is many times more simple.
If you build your Own PWM , there is no requirement to talk to the curcuit on the fan, and , if you overbuild it it wont fail.
OR
you can talk to the controller on the fan, with PWM pulses. but then you wont be able to control a non-pwm fan, so why would you build a controller that only works for some things?

the curcuit to do it, isnt that different, one mosfet difference, and full control at the controller, of ANY fan. not just a PWM fan, and every PWm fan too reguardless of thier communication needs.
So if you build a PWM controller as we have seen, you can put the one last component in and control anything, not just a fan that expects some specific pattern of pulses. even control your LEDs with it.

xXSebaSXx said:

As for controlling PWM fans bypassing the PWM circuitry... True; you can do it by just voltage regulation... But why would you spend the extra money on PWM fans if you're just going to use them as regular 3-pin fans?
.

Click to expand...

Good question? because it will still be a PWM 4 pin fan, and i can use it anywhere still, so even if i PWM it myself or voltage control it myself simply, it can go anywhere in the system?? because it was a great fan? because i am buying them for the same price, and it has an extra feature? i donno why?

xXSebaSXx said:

Another drawback of this approach is the fact that we are talking about high powered fans here... the weakest fan mentioned on here pulls 1.14 amps at 12 volts... that makes this fan a ~14W fan... The most powerful fan on this thread draws nearly 50W or power.... My guess is that if you go with resistors; you're going to need some mighty big ones so that they don't just burn off... and using those still leaves us with the fact that all that voltage that they are not sending to the fan is converted to heat that you're goint to be putting into the case... It kind of defeats the purpose of high powered fans if you're just going to be moving hot air around.

Click to expand...

completly, the PWM method, be it on your own controller , bypassing the fans curcuit or not, is much more efficent, but mosfets still do heat up but certannly not as many watts as resistive or linear regulation.

once you put in some resistance to the flow of current though, there wont be 50W for a 50W fan to dissipate in heat, the resister by default resists the flow of current too, less current flow, less fan, less current through the reister itself. but even 10W of heat would be BAD.

so it is a Waste, and it is useless heat, but not as bad as it sounds.
if i tune it down to 25W to the fan, there is an asumption that there will be 25W of heat pouring out the resister, i used to make that assumption. there are online calculators that will show the actual heat that will be dissapated by the resistance in a given situation.
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LOL...
This thread is turning into something so much complicated than it really needs to be. The OP wants a way or running high powered fans via PWM signal... To be quite honest; I'd just wire the PWM and RPM sensor wires to the MoBo header and feed the +12V and GND wires straight from the PSU...
That way you would have full control over the fans via BIOS/SW while still being able to run the high wattage monster fans shown here. No real need to put anything in between the MoBo and the Fan that way.... Yes; you'd be limited to whatever duty cycle the MoBo header is set up to, but any PWM control for free would still be better than now PWM control at all.

I got some hands on figures. i dont do math .
delta 1amp 12v 12W fan, requires a 4.8V drop to get to 1/2 power (not speed)
resister has .5A at 4.8V = 2.4W <--waste heat
fan itself only using 6W

for 1/3rd power
resister has about 7.3V drop at .33A = 2.4W <--waste heat
Fan using only 4W
all figures are approximate.

not gonna work to well like that, with that one. it keeps stuggling to survive at any voltage.
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Yea, that's what I said in my previous post in this thread.