DIY Circuit - Square Wave Generator for 4-Wire PWM Fan Speed Control

This is the first in a series of videos about this handy little PWM circuit which can be used to control the speed of 4-wire PC fans and (most) server fans. The dialogue was unscripted so it might be a little unclear at times, but if you have any questions about the circuit please let me know in the comments and I'll do my best to address them in future videos.
You can read the article here:
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And there is a very long thread about the experience here:
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[@33samogo]

So, the fan sink max. 10mA -5V PWM signal, you can control 50 fans at once with only one TL494 in single ended configuration on fixed 25KHz frequency (in your case frequency is changing and the frequencies below 20KHz are making additional noise). The circuit using TL494 contain only one capacitor/resistor to set the frequency and 10K trimmer for speed control! Additionally the PWM output from the fan can be used as feedback on TL494 to control the fan torque! The price of TL494 is the same as for 555, so the choice is easy. Thank you for your video, it was helpful for me to understand the difference between PWM driving and PWM controlling (the PWM driver is on fan circuit)👍

[@FanPhys]

Thanks for your comment. It will always be simpler to use a programmable IC for this sort of thing, but it is a lot of fun making analogue circuits with discreet components. There is a version of this circuit that uses LM311 which stabilises the frequency. It is more complicated but also a lot of fun to design and build the PCB layout. :)

[@AbhishekKumar1902]

thank you so much for TL494 idea 😊

[@BALA-6242]

Hi sir Can you post full video How to make the full circuit

[@FanPhys]

I plan to make a video soon - thank you!

[@nowanone4678]

What is the difference between your circuit layout and the ones on google search where the output pin has no connection to other pins, im planning to control a 24V 4pin fan using NE555P

[@Max-di3gw]

Is there a complete circuit diagram? (from DC in to 4pin PWM FAN connector) Thanks very much.

[@simpernchong]

Nice... video. Any idea something like this are on sale? I want to connect PWN fan directly with PSU. Thanks.

[@FanPhys]

Thanks! Yes you can get the Noctua NA-FC1 which is the same thing, but a digital version. But it is not suitable for very high powered fans, unless you power the fans directly from the PSU.

[@shaungutierrez9411]

There are 12v dc exhaust fans on Amazon with only a positive and negative leads coming from the unit. These fans (2ea.) look like pc fans. Could I use a 12 v dc dimmer (...typically for lights) switch to regulate the fan speed?

[@FanPhys]

It would depend on the power handling capability of the dimmer switch... if the fan draws too much power the dimmer switch might go pop. A safer bet would be a dedicated 12v fan speed controller.

[@gerald4027]

My computer server fans are 12 volts and 2.4 amps each.There is 6 fans.I am running a consumer MB in the case.The MB will only handle 2 amps per fan so I will have to build 6 of these to be safe or is there another way to do it?

[@FanPhys]

One circuit will easily be able to manage six fans, however if you want to control the speed of each fan independently then yes you will need six circuits. As a general rule I never power such fans from the motherboard, always directly from the PSU.

[@gerald4027]

@@FanPhys.6 fans at 2.4 amps each is 14.4 total or 172.8 watts.these are server fans,not standard fans.

[@seanwood5443]

@@gerald4027 yea but hes asking if this would work for his situation ?

[@DontMindMeMining]

great video, have you done 2 wire fan controller controlled by PWM mod ? i wonder what transistors should be good for 2 amp 12V fan

[@lobsangwhite]

Im looking for a controllet to run an phanteks t30, but I want to operate that fan to full voltage (12V) my question is, your fan is 12V also but your controller is 5V, why? and having on mind 12V constantly is feeding the fan, could the fan be broken when the potentiometer is a full capacity?

[@FanPhys]

Hey, sorry for the late reply. All PWM fans (with 4 wires) are designed to accept this 5V square wave signal, which is why the voltage has to be no higher than 5V. The signal is like a set of instructions that tells the fan how fast to go, and it cannot damage the fan. With the potentiometer set to 100% it is the same as if the controller was not connected and the fan is spinning at full speed. What I will say is that the Phanteks T30 already has a built in speed switch, so it may not be necessary to use a controller like this one.

[@lobsangwhite]

​@@FanPhys yeah, it's a bit late but it doesn't matter, both the noctua controller and the pahnteks fan have already arrived and you are right, at the end with the fan switch no controller is needed but I'm ok with that, I have even more control I guess 🤷‍♂️

[@FanPhys]

@@lobsangwhite The Noctua FC1 is a very good controller - it does much the same as this circuit with a couple of added features.

[@electricaloverlord2838]

My 4 pin server fans don't stop with speed control circuit without cutting power, is this normal? Also, when I connect the pwm cable of the fan to the gnd line of the power supply, the fans do not stop. It only runs at the lowest RPM

[@FanPhys]

Yes this is normal behaviour for some server fans - I have several fans which will not go below 2,000rpm. I have a version of the Delta fan in this video which is "PFC1212DE-6J32" and it has a minimum speed of about 1,500rpm at 0% duty cycle. Sadly, there is no way to change this because it is part of the fan's internal programming.

[@electricaloverlord2838]

@@FanPhys Thanks for your help. I decided to buy the Sanyo 9SG1212P1G06 12V 4A model. Can this product stop at 0% duty cycle? Have you used this model before?

[@FanPhys]

@@electricaloverlord2838 No problem! I haven't used the exact same model but I have the older version ending in "G01" and it will stop at 0% duty cycle. Just remember that some fans are custom programmed and may have different PWM behaviour, so there is no way to guarantee what speed any given fan will run at 0% duty cycle!

[@tyjohnston5889]

@@FanPhys Your feedback is awesome. Subbed. Thanks!

[@deathstrouke3943]

Can i use DC 6-60V 12V 24V 36V 48V 30A PWM DC Motor Speed Controller (PWM can i use that to control speed on delta fan

[@cmja09]

Great vid! I bought the Nidec UltraFlo 60mm, and wondering if it follows that same pin connection. 8:47 is it uniform? left to right Black-Red-Yellow-Blue?

[@FanPhys]

It is possible, but the best thing would be to find a datasheet which sometimes is the only way to get the correct pinout.

[@electrosound4595]

How to add a thermostat for tempreture based fan speed in this circuit? Please help me because I want to add a fan to my power amplifier so when amplifier is not much heat fan run veri low speed and if temperature rise the fan speed also increases. I have same 4 pin fan.

[@larranlee3288]

How would I make one for a 12volt 1amp fan?

[@FanPhys]

I'll hopefully be going through this in a future video. Stay tuned!

[@enejhv]

Can i purchase that controler

[@MrFathead]

Is this the same timer you used? NE556N Texas Instruments. I want to make this to control the same aluminium san ace fans in your other video.

[@FanPhys]

Yep that's the one - mine is made by a different company but NE556N is the chip designation.

[@MrFathead]

@@FanPhys Thanks man I will order some and see if I can control my san ace 120s. At the moment I just have them going full blast but it is a bit unnecessary and is wasting electricity and makes some noise haha.

[@vahagnmelikyan2906]

Does phanteks t30 12v have 5v pwm signal or 3.3 v?

[@markalves6712]

Will this controller work on these fans Panasonic BV-261WDH1B (heat exchanger 54.5vdc) and Embpapst DV6248/19P. (48vdc)

[@lamjack1551]

Can I ask is this only applicable for dc fan that will use your pwm controller?

[@FanPhys]

Yes - this only works with DC brushless fans that incorporate PWM control.

[@muratyigit7951]

Hi,If I want to use this circuit with 12v ~2.5-3ah fan and ntc, where and how should ntc be located.. do you have a mosfet or transistor suggestion?

i think you skipped along the video. this controller dosent use a mosfet or transistor. its for controlling 4Pin PWM fans and puts out an aproprate PWM signal to the 4th pin while the fan is always getting 12V.

[@hardnachopuppy]

Is there a way to make this circuit temperature controlled using a thermocouple or a thermistor without a microcontroller?

[@FanPhys]

I'm not sure - since there is a small voltage drop across the diodes, I don't think it would be quite as simple as replacing the pot with a thermistor. A good idea would be to breadboard the circuit and test it with a 100K thermistor and see what happens!

[@almightytreegod]

So I came across this video as I’m repurposing a whole lot of server fans to be fume extractors, and since I’m doing so many I was curious if you knew of a controller that already exists for this purpose. Found a few on Amazon but after testing 2 of them found they were only around 1khz and 4.5khz respectively, and didn’t seem to make any difference. Any ideas? I’d really appreciate any resources if you might know. Thanks!

[@FanPhys]

Hey! Yeah there is a 25KHz digital pwm controller made by Noctua called NA-FC1. It's quite expensive (I think) but it does the job well enough, and you can power the fans separately by molex or similar 12v supply.

[@almightytreegod]

@@FanPhys ah yeah, saw that one… it’s a bit pricey for what I’m doing, but thanks for the reply. I appreciate it!

[@thewindevtech]

Could you show all of your extreme fans you have? Would be Nice :D

[@AutodidactEngineer]

Yes please that would be awesome!

[@FanPhys]

If I can find the time, sure :)

[@thewindevtech]

@@FanPhys Yay :D

[@shibukumarsingh9966]

Please make one for intel stock fan love from india

[@testingbeta7169]

cool, these potentiometers are horrible, especially in areas with humidity. carbon would go bad and output jersk, its better to use sealed ones