PC motherboard: PWM 4 pins to 3 Pins digital converter.

[scrat]

Kiriakos defied me (and the matter was very simple), so I couldn't remain indifferent

Yesterday I had some spare time to try a very simple circuit made with what I had by hand.
Since I was trying to make something that didn't require tuning, instead of struggling with transistors I used an opamp (one of the cheapest and widely spread, LM358).
The circuit is a very simple power amplifier, the opamp drives the npn BJT to translate the 0-3.3V reference into a 0-12 V output with a max 300mA capability.
I simulated the PWM input with a potentiometer, while the output was given to a real fan (12V, 0.11 A). It works (of course!), but the output can't swing up to 12V, as expected, it only goes little above 10V. A diode should solve the swing limitation.

I'll make some other tests these days.

[oPossum]

The circuit is a very simple power amplifier, the opamp drives the npn BJT to translate the 0-3.3V reference into a 0-12 V output with a max 300mA capability.

With a 12 volt supply and and 6 volt output with 300 mA draw, the transistor will have to dissipate almost 2 watts - more than 3 times it's absolute max rating.

That is an obvious problem with your "working" circuit. There are more problems.

A diode should solve the swing limitation.

How??? Why not PNP transistor like TIP42?

[oPossum]

Is there any prediction , about the consumed energy of this buck converter ?

The on-board  fan header , looks in specs with:
12V 0.20A  ( 1700rpm) 90mm INTEL fan.
Or 12V 0.20A (1000rpm)  140mm.
 

The circuit itself uses very little current - less thn 10 mA.

[Kiriakos-GR]

Well , just from fear , to not damage the expensive motherboard and fan, I did the move and payed the price,  for this  Nanoxia " PWMX"  PWM controller.

It will arrive in a week or so.
This controller  and the company it self , called as German technology ...  what ever it called it did cost to me allot , because the shipping cost was a bit high, and I had to buy and some other little things , ( fan grills and dust filters ) so the shipping cost to become worthwhile.

Still , I care about the up come of this thread , and I will test the " publicly approved " circuitry  ,
my board has two PWM headers .

There is no need to say , that I am dying to see the inner world of this Nanoxia " PWMX"  PWM controller.
  

[scrat]

With a 12 volt supply and and 6 volt output with 300 mA draw, the transistor will have to dissipate almost 2 watts - more than 3 times it's absolute max rating.

You're right in the fact it can't regulate at 300mA on all the range with that particular BJT.
The fan doesn't draw its rated current at lower speeds (and so lower voltages) because its torque increases with speed, but it could happen that it gets braked (even stuck) and then the BJT can burn.
I was using the components I had by hand, and my fan (as I said above) is rated at 110mA. The transistor wasn't even warm.

An PNP will work better on one hand, but I hadn't one to test. It could have the same (but "reversed") problem, since it could be unable to switch off. One (or two) diode(s) should solve (partially, at least) the problem by adding a voltage threshold to opamp's output (see attached). A rail-to-rail opamp would definitely solve it.

I know it's a really stupid circuit, and I also know the buck converter will be much better (best efficiency, smaller components). Maybe I'm going to try that too, but I was looking for a simple solution that anyone could make without any tweaking.

@Kiri: this last move lets me down... Don't you rely on us?
Joking aside: can you tell us how much is this German robbery?

EDIT: the resistance above the diode has a "random" value, it must be reasoned a little.

[Kiriakos-GR]

This German robbery  cost about 6 - 7.50 EUR In Germany ..

Funny enough , I found the same part in Cyprus retailed at Just 4 EUR !!  
http://www.eshopcy.com.cy/show.phtml?id=PER.807855

But there was no easy shipping to Greece as available option. ( I had contact them )
The same shop has base also in Greece, but they do not cooperate.
I had to use only an Courier service , that would cost an crazy amount of money (Cyprus to Greece) .  

And so I got it for 6.88 EUR   (plus some other stuff) = 7 EUR shipping  ( 30 Total )  From the mother Germany.   
 

[scrat]

@Kiri: Funny... And then we complain about pollution, costs, Far East competition... If transportation is such a crazy thing...

@oPossum: I made a bit of reasoning, and discovered that the diode there is not feasible So PNP is needed. I think the diode should work for PNP, without the resistor, to avoid rail-to-rail opamp.

[oPossum]

A simple linear circuit.  Not built or tested.

[oPossum]

@oPossum: I made a bit of reasoning, and discovered that the diode there is not feasible So PNP is needed. I think the diode should work for PNP, without the resistor, to avoid rail-to-rail opamp.

A simple voltage divider will work well. For example 1k from base to emitter, and 3.3k from base to op-amp.

[scrat]

@oPossum: I made a bit of reasoning, and discovered that the diode there is not feasible So PNP is needed. I think the diode should work for PNP, without the resistor, to avoid rail-to-rail opamp.

A simple voltage divider will work well. For example 1k from base to emitter, and 3.3k from base to op-amp.

Should work, too.
Can you please explain which is your "thought process" to design transistor circuits with feedbacks, like the one you posted above? I know it's simple, and I can analyse it, but I won't be that good in producing it myself, so I ask.

[Kiriakos-GR]

Just find an nice document explaining about  PWM signals and fans ...

http://www.addausa.com/ppt/PWM.ppt

And this its an ready solution.
http://www.diodes.com/zetex/_pdfs/literature/pdf/SCMCBR1.pdf



I have to admit , that the PWM control system its a bit complex.
No one can see how complex it is , if he does not study just a bit , the principals about it.  



.

[TheDirty]

I used one of those chips a few years ago, well not the same chip, but an Analog dbCool chip that does the same thing.  It had configuration and reporting over USB to control three fans using PWM with two temp probes and a stall warning buzzer.  It controls standard 3 pin fans over PWM and has a method to check fan speed pulses only during the PWM 'on' pulse.

[sonicj]

Kiriakos,
im still not grasping the original intent of this circuit....

is it:
- the motherboard won't run without a pwm fan attached?
- do you want the motherboard to control fan speed or is a fixed speed adequate?
- do you want to be able to manually control fan speed?

btw, what fan did you purchase? is this to be a case fan or cpu?
cheers!
-sj

[scrat]

Just find an nice document explaining about  PWM signals and fans ...

http://www.addausa.com/ppt/PWM.ppt

And this its an ready solution.
http://www.diodes.com/zetex/_pdfs/literature/pdf/SCMCBR1.pdf

I have to admit , that the PWM control system its a bit complex.
No one can see how complex it is , if he does not study just a bit , the principals about it.

As sonicj says, this last link is somewhat confusing: this chip is designed to make a standalone controller for a fan, not an interface for 4-wire to 3-wire standard motherboard fan.

PWM principal (especially in this application) is simple, you're just partializing voltage to obtain, as an average, a fraction of it. If you see the fan as a DC motor, to regulate its speed you just increment or decrement the width of the slice of 12V you give it. The average voltage will increment or decrement in the same manner. The speed sense is taken from the tacho signal's frequency.

[Kiriakos-GR]

Kiriakos,
im still not grasping the original intent of this circuit....

is it:
- the motherboard won't run without a pwm fan attached?
- do you want the motherboard to control fan speed or is a fixed speed adequate?
- do you want to be able to manually control fan speed?

btw, what fan did you purchase? is this to be a case fan or cpu?
cheers!
-sj

1) The motherboard are capable to run  with  4 or 3 pins fan.
2) With three pins fans , the fan will work always at full speed . ( 12V input no speed variation )
3) The 4 pin fan , will use the PMW  signal ( pin No4 ) , so to adjust the fan speed as needed .

The PWM to DC converter , it will effect the voltage input of the three pin fan , and so it will start to have variable speed .

All motherboard headers have an 200mA DC output , enough current for specific fans , that does not need more than that.
And above I had posted an guide about  fan size VS rpm = 200mA

The top wanted in this wish list ,  its an easy to build PWM to DC converter.
This one will be able to handle ( or just about)  the 200mA  load.

The best ever solution it would be the one, that can supply more current up to 600 - 700mA ,
enough current to run  even the faster 120mm fans  ( 2400 - 2800 ) rpm  .

At the most PWM to DC converters , it looks that the addition of an potentiometer that limits the voltage output to an specific range , its an easy to do .

Well this looks useful , because I can use an monster size Panaflo FBA12G12H  12V 0.6A ,
to operate at lower rpm speed as max , and still to through large amount of silent CMF .  

The design posted by @TheDirty, looks great about the usability factor at list.
Three outputs, plus current amplifiers ( drivers ) that could handle anything, and possibly fans above the 200mA .    
    

Basically , anything that it can handle 800mA to 1A as current output , it would be called ,
the ultimate in specs  PWM to DC converter.
In this scenario , the output transistors  ( alike the 2N3055 ) they could draw amps by be powered,
by molex connectors.
With this design you can run any monster 120mm fan , at full speed with no fear.

My next move : To email Nanoxia about the max mA  output, that their controller are rated for.
 
  
I am aware of , that some of  my requirements, are possible to be made, and some not . 
 

 



    

[Mechatrommer]

2) With three pins fans , the fan will work always at full speed . ( 12V input no speed variation )

makes me confuse... if its constant 12V, why dont just use 2 pins (+ve -ve)? whats the 3rd (sense) pin is good for?
looking back at your OP, you said you want to control non PWM fan? and i ask... a non PWM fan got a sense output? if yes, then will it be compatible with 4pin sense input?

All motherboard headers have an 200mA DC output , enough current for specific fans , that does not need more than that.
The best ever solution it would be the one, that can supply more current up to 600 - 700mA ,
enough current to run  even the faster 120mm fans  ( 2400 - 2800 ) rpm  .

i suggest you stick with the standard, if the MB provide 4pins only and capable of 200mA only, then better stick to it, its not designed that makes the MB/CPU crash i think it means, the CPU will only need such amperage/wattage to do the cooling. earlier you made a thread on saving electricity, now you want to waste it by pushing to 600mA/higher limit. i admit that i've added some more fans inside my CPU (12V constant), but not to cool the CPU further, but to control dust entry and departure point so it will not enter randomly and stuck on top of the MB or other electronic stuffs. i trust the fan that comes with my CPU will do the job better enough.

now you want to make a tweak to the stuff you are not familiar with and expect somebody comes out with bulletproof and proven solution. i think you fight is not worth enough. thats why i still reluctant to struggle to google on better solution for you and keep rambling nonsense'ly, even if i have the capacity and knowledge. not only the electricians have blown things up you know! electronicians too, but more dangerously, in a silent manner, sometime even more difficult to trace the blast point. you adviced me/us something... that i will give it back to you... you said "dont give the advice to kids, they can do some dangerous stunt" sounds something like that. and i know you are not kid, so i'm advicing... with respect, its for your own good. its your MB you are playing with! unless you are willing/ready to scrap that? Cheers

ps: any info here are good though, given the right purpose for it and you really know what you are doing, especially increasing (overclocking) the wattage of the circuitry involved.

[Kiriakos-GR]

2) With three pins fans , the fan will work always at full speed . ( 12V input no speed variation )

makes me confuse... if its constant 12V, why dont just use 2 pins (+ve -ve)? whats the 3rd (sense) pin is good for?
looking back at your OP, you said you want to control non PWM fan? and i ask... a non PWM fan got a sense output? if yes, then will it be compatible with 4pin sense input?

shafri dot not kill your self ... with generic thinking ..
The motherboards PWM  circuitry its an design, designed by INTEL , the  " how-to "  its described on the first post links.
http://www.pavouk.org/hw/fan/en_fan4wire.html

The three pin one , same story ....  + /-/ Sense/  
At the old three pin header (CPU header) ,  this was able to control the DC ..
Today the default  (CPU header) its the PWM , that partially supports the  three pin fans. 

  

All motherboard headers have an 200mA DC output , enough current for specific fans , that does not need more than that.
The best ever solution it would be the one, that can supply more current up to 600 - 700mA ,
enough current to run  even the faster 120mm fans  ( 2400 - 2800 ) rpm  .

i suggest you stick with the standard, if the MB provide 4pins only and capable of 200mA only, then better stick to it, its not designed that makes the MB/CPU crash i think it means, the CPU will only need such amperage/wattage to do the cooling. earlier you made a thread on saving electricity, now you want to waste it by pushing to 600mA/higher limit.

All that I suggested - wished , was the PWM to DC converter to was able to amplify "some how" the output from 200mA to 700mA ...  is this a Sin ?    

Plus , one such capable circuitry, has lesser chances to burned out.

[Kiriakos-GR]

What I plan to try , its to drive with the Nanoxia PWMX an BD135 , if this is able to cooperate, I just got up to my target.



 

[Mechatrommer]

What I plan to try , its to drive with the Nanoxia PWMX an BD135 , if this is able to cooperate, I just got up to my target.

if you'd be more specific, then it will be easier for the rest of the "geeks" i think

[scrat]

What I plan to try , its to drive with the Nanoxia PWMX an BD135 , if this is able to cooperate, I just got up to my target.

if you'd be more specific, then it will be easier for the rest of the "geeks" i think

Maybe it's not so easy to the greeks to be easy for the geeks.
Sorry for the nonsense, perhaps I'm suffering for low glucose level in my blood...

[Kiriakos-GR]

No problem mate ,
I have too much sugar in my blood , and so I drink coffee with out sugar,
and this causes to me , an over excitement    

[scrat]

Ok, after a good dinner one recognizes the madness of previously done things... I was just wandering your reaction (my sentence involved the Greek, but just because of a rhyme reason). I enjoy seeing you're a tongue-in-cheeck (a composite word I never have read, but Wordreference suggests it) one too. And you must be sweet (not that this moves my interest, let's state it!), if you have so much sugar in your blood.
Enjoy a good coffee, but beware of over excitement!

[sonicj]

1) The motherboard are capable to run  with  4 or 3 pins fan.
2) With three pins fans , the fan will work always at full speed . ( 12V input no speed variation )
3) The 4 pin fan , will use the PMW  signal ( pin No4 ) , so to adjust the fan speed as needed .

The PWM to DC converter , it will effect the voltage input of the three pin fan , and so it will start to have variable speed .

...............

ok, i understand now!

that panaflo looks like it has quite the following! i have older media center box with nothing but FBA08A12L's. oldskool 

i recently built a box with a Noctua 120mm case fan. silent computing has come a long way since i last messed with those panaflos! the noctua is truly amasing! the little bit of noise it does make is like nothing you've ever heard before.

i don't have the time to try this, but what about a lm317 with appropriate RC to convert the pwm to dc reference?
-sj

[Mechatrommer]

i don't have the time to try this, but what about a lm317 with appropriate RC to convert the pwm to dc reference?

There is no try, either do or dont to be able to enter "Kiriakos Design Contest", you must provide a sound and "proven to be working" schematics. he dont want anything that involve any explosion.

[PeterG]

The speed of a 3 pin fan header can be adjusted. The mobo bios must be set to manual fan speed and an app like Speedfan used to control the speed of the fans. The third pin is used for tach only. The speed on the 3 pin fans is controlled with voltage rather than pwm.

Regards