So you want PWM control of your 3-pin fan?

I had to start a new thread because I couldn't update the old one.

Here's the improved mosfet version of the 4pin pwm to 3pin fan circuit. This is closer to Intel's spec which allows for up to 5.25v pull-up and 5ma on the pwm pin. This is 5.15v and 1.2ma. Any logic-level n-channel mosfet capable of a few amps will work fine.

Tested, working. Enjoy.

 

Man I wish I had paid attention in Rocket Science class.

 

Are there any photos of the mod available?So we need an N channel mosfet right?
And is that a diode?

Will any of these mosfets do http://www.markidis.gr/index.php?cPath=32_534_648&language=en
Which one would be best?

 

I used an NTE2985 (30a TO220) because I had them on hand. Make sure you use a logic-level n-ch mosfet. The diode is a zener rated for 5.1v NTE5010A. Sorry for the quick drawing but that should get you going.

G = gate
D = drain
S = source

P = PWM
T = Tach
+ = 12v
- = GND

 

Nice sketch makes complete sense...But it might be quite costly dont u think...mosfet and diode will get to 10EUR maybe..Still i might try this just for encyclopedical reasons!
Thanks again!

I suppose this is for 1 fan only right?

 

If you get your power (and probably ground also) from a molex, you can put a dozen fans on it.

It's not expencive at all. I'm in the states but a cheap logic-level mosfet is $1, the diode maybe $0.10, and resistor $.05 but I buy a 10-pack at a time. It was very cheap to build. I've spent more on a package of zipties.

IRLz24 17a $0.62

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRLZ24PBF-ND

 

Here's another version I've been working on. Feel free to make suggestions that may aid it's performance.

This is a high-side switched transistor version that has a minimum speed adjustment. This will allow ANY 3-pin fan to be adjusted to (roughly) meet Intel's minimum RPM spec of 30%.

My software didn't have a good TO220 NPN for the output transistor but any NPN capable of a couple amps should be fine. Radioshack has a TIP3055 that's good for up to .5a without a heatsink and a few amps if you sink it.

 

this has no feedback capabilites from what I can see

 

i need to control a PWM fan.

any simple way to do that?

its a high current fan so i cant use a fan controller.

i just need pwm signal generator that is variable.

 

Feedback for what?

Just a 2-wire fan? Doyou want the cheap and easy way or do you want to build it yourself?

http://www.electronickits.com/kit/complete/motor/ck1400.htm
or
http://www.electronickits.com/kit/complete/motor/k166.htm

Something like that can control a fan. The second link is a MUCH better design. Either one could have the potentiometer replaced with a thermistor.

To build your own, look into the SG3525 PWM IC but it has it's limitations as a motor controller. Mainly it can only go to 99% do to the dead-time built into the IC. It's designed for push-pull convertors but the output can be paralleled to give you more like 0-99% PWM.

Here you go. This would be the cats ass for cheap controllers.
http://www.virtualvillage.com/12v-1....html?utm_source=googlebase&utm_medium=shcomp

$10 bucks cheap enough for you?

http://cgi.ebay.com/LED-Dimmer-Adju...emQQptZLH_DefaultDomain_0?hash=item2a02f2011c

 

No rocket science here mate, just basic electronics!

 

none of those will work.

i need pwm signal generator.

my fan is 4wire.

+,-,rpm,pwm

 

The SG3525 is a PWM generator. You could even use a 555 to create a pulsetrain the fan would respond to.

Actually Fit, any motor controller would work. All the ones I showed you would work. Just put the controllers M- terminal to the PWM pin of the fan This will give you a PWM signal capable of driving a 4-pin fan. The difference would be that the control works backwards. A DC motor controller just grounds M- at the PWM width and frequency to raise the motor's speed. The Intel 4-pin signal pulls the PWM pin low to lower the fan's speed. Same as the DC motor controller just backwards so just turn the knob the other way.

 

sub

 

I only sing up to thanks Lazzer408. The firts basic cirtcuit works very well. Thank you a lot!!. The only issue is the tachymeter, it display erratic values and the cooler varies alittle it speed constantly.

Thank you again!.

PS: Sorry for revive an old thread.

 

It will due to the fan being low-side switched. In other words, the PWM is also chopping the tach.

 

Anyway, while that does not damage the fan... that makes the main work, control the fan.
Thank you again!.

 

I also only signed up because of this thread, I've been looking for something like this for a little while because PWM fan selection is a lot more limited than 3-pin, so it would be great to be able to control a 3-pin as easily as a PWM. First of all, I wonder if you could point me towards some kind of crash course in basic electronics so I can understand what I'm doing a little better? I do have some experience working with designing and building circuits, but the last time I did anything like this was about a decade ago, so I'm beyond rusty.

Now, I am curious about your second circuit... You say it is high-side switched rather than low-side, so would it avoid the problems described by Xander? I would also like to expand it to handle more fans and be powered by molex in the way you mentioned earlier. How would you recommend going about this? Lastly, for now at least, I've noticed that commercial fan controllers and hubs almost always include some hefty caps with the reasoning described as this would allow them to handle more watts per channel. Neither of your circuits have any caps, so I'm wondering if you don't think they are needed, or if you just didn't add them because you weren't planning on running that much power through them?

Thanks.

 

Thanks but for the time and money, I think id just go buy new fans and be done with it.

 

I won't dispute the time you'd put into making something like this, but money is definitely another story indeed. I run 5 fans in my case, with the option for another 5 if I really wanted them. Just to replace the 5 I've already got with PWM versions of the same fans would cost over $100 whereas the parts that would go into this circuit would cost no more than $15 and probably less than $10. Add to that the fact that there are a lot more options when it comes to non-PWM fans than the reverse and something like this could give you a lot of flexibility in your case cooling design for a fairly low cost.

 

Oh I totally understand but for me and the local shops around they only sell bulk pcks of 50 piece's and the price is ridicules.

 

That would definitely make it difficult

 

Yeah does so. I love pulling out the soldering iron but like I said these guys are dicks. I have a 56" dlp led TV and the cap's keep blowing in the power supplie from the HS to close to them.

Do you think they'd sell me the caps i need for actuall value? Nope... costs me $125 just to get them to do the 15 min job,

 

Any chance of getting them from an online supplier? Might take a little extra time, but maybe it would solve the problem.