Intel's 4-pin "PWM" Connector

DIY Fan Controller for PWM Fans

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Intel's 4-pin "PWM" Connector

Intel's 4-pin "PWM" Connector

Introduction

I’m sure that most hardware enthusiasts are no strangers to dalliances with DIY, whether it be case modding, component modding, or custom cooling.  However, when it comes to building parts of your computer from scratch, the tally of enthusiasts who can claim this prestige most certainly diminishes.  Fortunately this neat fan controller project requires only a little time, expense, and commitment, and the circuit is relatively easy to build and very satisfying to use!

First Things First…What is PWM?

PWM stands for Pulse Width Modulation and is, among other things, a very clever means of controlling power to electrical devices: in our case a DC (direct current) fan motor.  Although you don’t need to understand the ins and outs of PWM, it helps to have an rough idea about how PWM works, so here’s a very quick explanation.

Think of a PWM signal as if it were a beating heart.  Rather than being powered by a continuous supply of power (which would ordinarily be the case) our DC fan motor is being fed with pulses of power; it is essentially being switched on and off very rapidly.  These on-off pulses are delivered to the motor several thousand times per second, and because the intensity (or width) of each pulse can be changed, so the speed at which the motor turns can be changed.  The image below shows how different pulse widths affect the resulting power of the PWM signal:

Three different PWM signals showing average voltage

PWM Controllers vs. PWM Fans

There are PWM controllers and there are PWM fans, but the way in which PWM is implemented in each differs greatly:  a standard PWM controller modulates the 12 V supply line of an “ordinary” 12 VDC motor. Conversely a PWM controller for PWM fans – such as the one featured in this article – doesn’t modulate the 12V supply line but instead sends a PWM signal along a different supply line (the magic “fourth wire”) to a more advanced 12 VDC motor, leaving the 12 V supply line uninterrupted.  Designated PWM fans not only have internal circuitry which differs from that of standard fans, but because they are designed with speed control in mind the motors themselves are usually more advanced (and expensive).  So, PWM speed control of a standard fan is indeed very different from PWM speed control of a PWM fan…  Nidec even goes so far as to say that modulating the main supply voltage is not advisable:

Pulse-width modulation of DC operating voltage to modify fan speed is not recommended. Transients generated by that approach can irreversibly damage motor commutation and control electronics and dramatically shorten the life of a fan.

The Circuit

Here is the circuit which was originally obtained from Nidec’s website, although I found it in the overclockers forum:

Nidec's Simple PWM Circuit

Nidec's Simple PWM Circuit

Components

  • 555 Timer IC (Integrated Circuit)
  • Capacitors:  C1 0.01 μF; C2 680 pF; C3 10 μF; C4 0.1 μF
  • Resistors:  R1 1k
  • Potentiometers:  P1 100k
  • Diodes: D1 & D2 1N4148

Building the Circuit

Now before you allow yourself to become intimidated by the above schematic and all these different components, make sure you are taking a calculated approach to the process of putting the circuit together.  The best thing to do is to take it one step at a time. Having done it myself (several times),  these are the steps that I find most conducive to hassle-free workflow:

  1. Plan your circuit on a piece of paper, familiarizing yourself with each component (learn what it looks like and what it does) and the layout of the circuit, and taking time to arrange it in such a way that it is clean and clear.
  2. Working from your plan, carefully assemble the circuit on a breadboard.
  3. Check and re-check all the connections.
  4. Connect the circuit to a power source – preferably a spare power supply that is not hooked up to a PC – and check to see if it works.
  5. Debug (identify problems and deal with them) if necessary.
  6. Again referring to your circuit plan, assemble the circuit on stripboard.
  7. Work on the presentation of your controller – eg., put it in a project box or into a drive bay.

Step 1:  Organize Your Components and Print a Plan of the Circuit

These are all of the components you need for the circuit

These are all of the components you need for the circuit

So, now you know what each component looks like.  Once you have your components arranged spaciously on an uncluttered flat surface (as above), get your breadboard ready!

Step 2:  Breadboarding

Components set out ready for breadboarding

Components set out ready for breadboarding

The wonderful thing about breadboarding is that it doesn’t have to be neat or tidy…or even compact.  The point of breadboarding a circuit is to give you, the “beta tester”, easy access to each and every component and connection, allowing you to quickly sort out problems and get your circuit up and running without having to worry about making permanent connections.  Here are a few simple pointers:

  • Take your time and keep your work area uncluttered.
  • Make sure your hands and fingers are clean before you start.
  • Use single-core wire for good connections to the breadboard tracks.
  • Leave some room around each connection/component to reduce the risk of shorting.
  • Remember to firmly press (but not force) the components and wires into place.

Step 3:  Check and Re-check the Connections

Carefully check that all terminals and pins are seated correctly

The reason this step is so important is that you are checking the connections solely with the power of observation; the breadboard should not be connected to a power source yet, and it is crucial that you carefully check each connection before the circuit gets anywhere near live wires.

Step 4:  Connect the Circuit to a Power Source and Test with a Fan

Breadboarding done and testing in progress!

Breadboarding done and testing in progress!

Connecting the breadboard to a live power source is, and always should be, the last thing you do (especially if you are a n00b, like me).  It is also advisable to use a spare/unconnected power supply, because if you happen to be so unfortunate as to cause a short circuit using the PSU that is connected to your computer, it may seriously damage the PSU and/or one of your PC components.  I can attest to this – my first attempt at a fan controller some weeks ago fried my treasured £300 Foxconn motherboard.  The PSU is fine (and has survived at least three further short circuits), however my experience tells me that even a good PSU like mine which has commendable SCP (short circuit protection) doesn’t guarantee the well-being of your components.  You have been warned!

And remember:  This circuit uses 5v, NOT 12v.

Step 5:  Debugging

Digital Multimeter - a must for testing circuits and components

Digital Multimeter - a must for testing circuits and components

Circuits generally don’t work the first time around, so be patient and acknowledge that you will probably have to do some debugging somewhere along the line.  It’s not a big deal, and although it may involve a fair bit of work, don’t worry about it – I had to debug my circuit (and in some ways I am still debugging it), and I had the overclockers.com forum community helping me every step of the way as I’m sure they will help anybody else who seeks assistance.  To make your life is a lot easier, get a digital multimeter if you don’t already have one.

Step 6:  Stripboard, Solder, and Sweat

My stripboard layout, created in MS Paint

My stripboard layout, created in MS Paint

When the time comes to make a proper circuit using scary grown-up tools like a soldering iron and a pair of wire cutters, it is definitely worth your while planning the layout of your circuit once again and trying to make it as compact as you can.  If you have space on your stripboard you might want to consider soldering a 4-pin fan header onto it to keep the controller tidy and practical.

The layout that I chose (above) is almost identical to the schematic of the circuit, which helped a great deal when the time came to put the circuit together and make sure all connections were made in the right place.  Stripboard has copper tracks that run along the underside of the board, so you must plan your circuit to accommodate these tracks and remember to break the tracks where necessary.  Here is a picture of the underside of my stripboard where the 555 IC is, hence the broken tracks:

Breaking tracks in the stripboard

Breaking tracks in the stripboard

Here is a picture of what is possible if components are extremely well laid out – this particular circuit was built by Martinm210 at overclockers.com forums and features a slightly different PWM generator using a 556 IC (two 555’s in one package) – see below for a schematic of this circuit:

Martinm210's PWM generator

Martinm210's PWM generator

Step 7:  Presentation

This is the icing on the cake.  You have finished your controller, but you don’t like the bedraggled morass of wires and terminals sitting beside your uber-modded and meticulously maintained gaming rig… so what should you do?  There are a number of answers, and it really comes down to what you want to use the controller for.  I use my controller for testing (well, playing with) very powerful PWM fans, so I packed it up inside a neat little project box to make it look a little more sophisticated and to make it more practical too:

The finished PWM controller

The prototype PWM controller

Project in a project box

Project in a project box

Developing the Circuit

As it is, the circuit should work well with most if not all PWM fans that you are likely to find in a hardware enthusiast’s box of tricks.  If, however, like me (and a few others) you want to engage in some turbulent tomfoolery with ludicrously powerful 12VDC fans (see below), you will need to boost the PWM signal or create a different PWM generator altogether which uses a 556 timer instead of a 555.  The circuits described below are featured in this exciting thread at overclockers.com forums.

Using Two 555 Timers

Here is a schematic of the dual-555 PWM generator.  This circuit boosts the existing PWM signal using an “inverted schmidt buffer” which was suggested by bing at overclockers.com forums:

A more powerful PWM generator

A more powerful PWM generator

Using the 556 Dual Timer

The 556 timer is a single 14-pin package which contains two 555s.  If you would rather build the more powerful 556-based PWM generator like the ones Martinm210 and Brutal-Force put together, here is the schematic (again, courtesy of bing):

556 Dual Timer circuit

556 Dual Timer circuit

(Components are identical to the 555 circuit but are labeled differently in this schematic:  C1 = 680pF; C2 = 0.01 μF; C3 = 0.1 μF; C4 = 10 μF, polarized.  There is also an extra resistor (R2) which has a value of 10K.)

The 556 Circuit on the breadboard

My 556 Circuit @ breadboard

Complete 556 circuit on a stamp-sized piece of stripboard

Complete 556 circuit on a stamp-sized piece of stripboard

Simple 4-pin Molex interface for the PWM controller

The box for the 556 circuit, complete with stylish aluminum pot and Molex connector for convenience

Two 4-pin fan headers for now

The business end of the controller - for me, two fan headers are plenty

Monstrous 260CFM 48W San Ace PWM Fan

Monstrous 260CFM 48W San Ace PWM fans

Final Thoughts and Video

First and foremost, make sure you take your time if you decide to build this (or any other) circuit for use with your system – working with electricity is hazardous (and if not for you, certainly for your hardware!) so be careful.  I’ve shorted my PC (yes, my entire system) no fewer than FOUR TIMES since I started messing around with DIY fan controllers, and unfortunately one of these shorts fried my prized Foxconn X58 motherboard.  Suffice to say, I have been more cautious since.

On the plus side, these fan controllers are a lot of fun and can be very useful if you regularly benchmark your system and require powerful cooling at the touch of a button (as I do).  Here’s a short video which shows the capabilities of the 556 circuit when paired with some seriously powerful 120mm fans…

Thanks

Primarily I’d like to thank I.M.O.G. for playing such an important role in my PWM fan projects (he organized the purchase and international shipping of the San Ace fans for me – top dude!) and for giving me the opportunity to write this article.  I’d also like to thank Brutal-Force for his videos and his thread which inspired me to make a PWM fan controller in the first instance, and resident electronics expert, bing, who freely shared his electronic expertise and offered valuable assistance throughout the learning process.

– Dave (LennyRhys)

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Discussion
  1. GuineaPig
    I did 3 rebuilds, nothing changed. Tried it with my PC-CPU Fan, nothing changed.

    Is it because I'm using an 555NE and not a 555 CMOS?


    The 555NE and 555 CMOS is the same thing. Recheck all the connections and the parts, if any part is the wrong part it won't work right. I say this because I've had to recheck and found a wire in wrong place or wrong part. Also from your picture, it looks like the cathode of both diodes are connected, it could be from the angle the pic was taken.
    Final drawing:

    SMT & Through Hole combo:

    The SMT parts have the "a" in the ref number, C4 is for through hole ceramic cap (yes they make 10uf ceramic caps), C4b is for electrolytic cap.
    GuineaPig
    Thank you very much for your How-To! It is awesome! I build it myself and have a problem now. I'm a... well can't really say "noob" but not so well educated in the electronic circuits-area.

    I can only controll the top 10% (I think) of the speed range of my fan. It is a Arctic F12 PWM PST.

    I am not using this fan for my PC, instead I'm using it to create an (small) airflow in my room to prevent mold.

    Currently I use the dual 555-Timer solution but there is no difference in the control in comparison with the one 555-Timer-Circuit.

    This is my Circuit. Hopefully labled everything important (those Diodes are standard 1N4148)

    Is there a way to increase the range? Or am I doing something wrong? Suggestions?

    Thank you in advance!

    (Sorry if I upset somebody with my spelling and grammar. Not a native english-speaker)


    Your English is better than some people here in the USA :)

    It looks like you got everything but a little hard to tell in that rats nest of wires :rofl: Try a different fan and see if it does the same thing, if that don't work, check then recheck and check again then check again :) to make sure the connections are in the right place, even techs can get a wire misplaced now and again :rofl:

    I like your breadboard, take a look at mine:
    Thank you very much for your How-To! It is awesome! I build it myself and have a problem now. I'm a... well can't really say "noob" but not so well educated in the electronic circuits-area.

    I can only controll the top 10% (I think) of the speed range of my fan. It is a Arctic F12 PWM PST.

    I am not using this fan for my PC, instead I'm using it to create an (small) airflow in my room to prevent mold.

    Currently I use the dual 555-Timer solution but there is no difference in the control in comparison with the one 555-Timer-Circuit.

    This is my Circuit. Hopefully labled everything important (those Diodes are standard 1N4148)

    Is there a way to increase the range? Or am I doing something wrong? Suggestions?

    Thank you in advance!

    (Sorry if I upset somebody with my spelling and grammar. Not a native english-speaker)
    mattlach
    So, the PWM controller is done, and works great.

    It's butt ugly, but it works great.

    Here it is, sealed up with some hot glue, just so nothing shifts around and causes a short:



    I ordered a 3 pack of extra drive bay covers from corsair so I could chop one up and install switches and the pot with a dial on it to control my fans.



    Middle switch: Fans On/Off

    Right Switch: Fans Manual control or auto control based on water temp (if middle switch is on)

    Dial: Controls fan speed via PWM



    Turns out the front panel on Corsairs Obsidian series bay covers is textured sheet metal. It is glued somehow to the plastic part of the bay cover underneath. I pried the metal part off using a contractor knife. The goo from the glue was intense. Took lots of goo-off to clean both sides. Then I carefully drilled/dremeled holes to fit my two switches and my pot dial in the metal front, and went nuts with my dremel on the plastic to make everything fit in the back.

    I was going to glue them back together again, but I think the screws that tighten the switches and pot to the panel do the job, so it's not needed.

    The hole locations weren't exactly perfect. I measured them precisely, but kept slipping with the damned drill when I went to drill them. Should have used a punch to start the holes, but I couldn't find mine. I don't think I can tell that they are misaligned, but if it winds up bothering me, I have three more spare Corsair drive covers to re-do it on. :p

    I wiped the damned thing down, but it appears to be statically charged, and clings to all the dist from my dremeling. Will have to do a more careful cleaning when I put it all together.


    If anyone is curious, this is what the final result looks like once installed in the case. (I really should have wiped down the front better before taking this picture, and maybe I shouldn't have been lazy and used my DSLR instead of my cell phone :p )

    Click for larger:



    I'm by no means a seasoned case modder, but I am happy with how it turned out. It's not perfect, but neat enough, and it definitely works as intended.
    So, the PWM controller is done, and works great.

    It's butt ugly, but it works great.

    Here it is, sealed up with some hot glue, just so nothing shifts around and causes a short:



    I ordered a 3 pack of extra drive bay covers from corsair so I could chop one up and install switches and the pot with a dial on it to control my fans.



    Middle switch: Fans On/Off

    Right Switch: Fans Manual control or auto control based on water temp (if middle switch is on)

    Dial: Controls fan speed via PWM



    Turns out the front panel on Corsairs Obsidian series bay covers is textured sheet metal. It is glued somehow to the plastic part of the bay cover underneath. I pried the metal part off using a contractor knife. The goo from the glue was intense. Took lots of goo-off to clean both sides. Then I carefully drilled/dremeled holes to fit my two switches and my pot dial in the metal front, and went nuts with my dremel on the plastic to make everything fit in the back.

    I was going to glue them back together again, but I think the screws that tighten the switches and pot to the panel do the job, so it's not needed.

    The hole locations weren't exactly perfect. I measured them precisely, but kept slipping with the damned drill when I went to drill them. Should have used a punch to start the holes, but I couldn't find mine. I don't think I can tell that they are misaligned, but if it winds up bothering me, I have three more spare Corsair drive covers to re-do it on. :p

    I wiped the damned thing down, but it appears to be statically charged, and clings to all the dist from my dremeling. Will have to do a more careful cleaning when I put it all together.
    Got my 680 pF capacitors and replaced the incorrect one today. Everything works :)

    At first I thought it didn't, because there is a noticible delay in the circuit when going from the minimum setting up to higher settings. Presumably this has to do with capacitors charging? The delay appears to be minimal when shifting between non-lowest settings though.

    I have done a ****ty hotglue strain relief/conformal coat because I was concerned about things shifting and conductors touching. Once it dries and I cut my board down to size I will post my (very ugly, but functional) pictures.
    WhitehawkEQ
    I use this zoom-stereo-boom-microscope, I find I can control my hands better when I can see that small :)


    I tried using something like that a few years back when I - two weeks after launch - slipped with a screwdriver when taking the cooler off of a Radeon HD 7979 in order to try to custom mount an h80 cooler on it.

    They had these stereoscopes in the labs at worn so I triwd using one to fix the traces I accidentally cut. I was never able to do it.
    WhitehawkEQ
    No, not double jointed, it's Swan neck deformity as a result of Lupus. It's affected my tendons and ligaments in the bone joints in my hands, arms, shoulders, knees and feet.


    I'm sorry to hear that :(

    WhitehawkEQ


    As for that cap, it won't hurt anything having the wrong value in the circuit.


    Much appreciated! Thank you!
    mattlach
    Double jointed? Nice.


    No, not double jointed, it's Swan neck deformity as a result of Lupus. It's affected my tendons and ligaments in the bone joints in my hands, arms, shoulders, knees and feet.

    As for that cap, it won't hurt anything having the wrong value in the circuit.
    WhitehawkEQ
    I have a feeling that 680pf cap you have is really a 680uf cap, post a pic of an unused cap showing the value of the cap.

    edit: You do have the wrong cap (see pic below)



    Holy ****, you are right, it is. I thought it was kind of odd it was so large, but I went with it.

    The packaging they came in definitely says pF, but the writing on the side of the cap itself says uF.

    I feel like I should have verified that. I work in quality and I know all abut incoming inspection, just didn't think to do it for my own home project!

    Any chance the discharge from a capacitor literally a million times larger than intended might have done damage to the rest of my parts or the IC, or should I be OK to just remove the offending part and replacing it with the correct one?

    WhitehawkEQ
    You think you have it bad :rofl: I soldered all the parts on that little board with these hands.



    Double jointed? Nice.

    Yeah, I just have ordinary hands, but they are on the large side making detail work difficult. Add to that that they shake while doing fine detail oriented work as well. Makes it difficult.

    Strip boards are tiny enough for me, and just about the smallest I could possibly work on. Anything surface mount or professional PCB would be a pipe dream for me.
    mattlach
    Well, this thread appears to be mostly dead, but I figured I'd post my follow-up anyway.

    I finished my 556 based circuit but something is wrong.

    I have double and triple verified that my connections match the diagram, and double, and triple checked for any shorts anywhere.

    My behavior is that with the pot turned all the way counter-clockwise, the fan is at minimum speed. Turn the pot clockwise and nothing happens until the pot maxes out, at which point the fan suddenly switches to maximum speed. From this point if I turn the pot counter-clockwise again the fan stays at maximum speed all the way until I reach the minimum setting, at which point the fan switches to its minimum speed again.

    I noticed that I didn't wind up with exactly the same components as the op. my 680pf - when I received my order - wound up not being a ceramic disc capacitor but rather was electrolytic, and thus polarized. I soldered it such that the negative pole was on the ground side, and figured it wouldn't make a difference, but maybe it does?

    I have ordered another set of 680pf capacitors to check if this is the culprit.

    Here is more of a closeup:



    I'd appreciate any suggestions!


    I have a feeling that 680pf cap you have is really a 680uf cap, post a pic of an unused cap showing the value of the cap.

    edit: You do have the wrong cap (see pic below)
    Well, this thread appears to be mostly dead, but I figured I'd post my follow-up anyway.

    I finished my 556 based circuit but something is wrong.

    I have double and triple verified that my connections match the diagram, and double, and triple checked for any shorts anywhere.

    My behavior is that with the pot turned all the way counter-clockwise, the fan is at minimum speed. Turn the pot clockwise and nothing happens until the pot maxes out, at which point the fan suddenly switches to maximum speed. From this point if I turn the pot counter-clockwise again the fan stays at maximum speed all the way until I reach the minimum setting, at which point the fan switches to its minimum speed again.

    I noticed that I didn't wind up with exactly the same components as the op. my 680pf - when I received my order - wound up not being a ceramic disc capacitor but rather was electrolytic, and thus polarized. I soldered it such that the negative pole was on the ground side, and figured it wouldn't make a difference, but maybe it does?

    I have ordered another set of 680pf capacitors to check if this is the culprit.

    I'd appreciate any other suggestions, anyone might have.

    Here is my board layout (click for larger)



    The red wire on the right is my PWM out. Because I ran out of space I soldered the diodes in-line with the wires to my pot, and covered them in heat shrink sleeving. Note the massive 680pf electrolytic capacitor instead of ceramic disc capacitors. As mentioned above, just in case this is the problem, I have ceramic ones on their way.

    Here is more of a closeup:



    I have no pride in my soldering abilities. I don't have the steadiest of hands. This is the best I could do taking it nice and slow and spending several hours on it. It's not pretty, but I have checked for any bridging between strips, and I don't think there is any. Just as a precaution I hvae scratched the **** out of the insulating row between the strips to remove anything that might be bridging them, to no avail.



    I'd appreciate any suggestions!
    Hey all,

    Long time lurker around here, but first time poster.

    This is a great guide, and while I am no stranger to the soldering iron, my knowledge of circuits is somewhat limited.

    Could anyone explain to me in layman's terms the difference in end results from using the single 555 design vs going for the 556 (dual 555) design?

    Essentially, all I need is to be able to control the duty cycle for a single wire, I intend to attach to pin 4 on a PWM fan splitter, preferably from 0% all the way up to 100%.

    Also, jeez, the strips on the strip board seem awfully small. How on earth do you avoid shorting them together when soldering?

    Much obliged,

    Matt