Pulse Width Modulation EXPLAINED
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- Опубликовано: 10 май 2018
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Knew the PWM thingy already , but luv getting re-schooled/refreshed on these topics (cause Iam old :p ) as SS makes these vids so interesting vs online reads or paperback.Thaaaanks Greg
Glad you enjoyed it!
MrStereo55 same here. I try to watch all of Greg's videos, even if I'm well versed on the topic. I usually still learn something because his videos are so in depth and they cover the topic fairly well.
I knew about PWM and how it worked, but dammit I learned something new. You got me again, Greg. Nice vid, as always.
I learned quite a bit from making this video! Glad you enjoyed it.
Who Cares Gopnik detected
Jarmund: *Squats while establishing communism*
FANTASTIC explanation, Greg. Your use of a guitar to explain the amplitude and attenuation was clever and incredibly helpful. One of my favorite videos of yours so far. It felt very much like an "Engineering Explained" but for computers rather than for cars/mechanical-engineering.
I had a vague idea of what PWM fans were but this video gave me a better understanding.
never stop making informative vids like these thanks man
nice man, good informative video. Love to see this kind of content, I use and suggest your videos to people getting into PC building and videos like this make explaining things sooooo much easier.
Very nice explanation, I never really understood how the fans could be getting constant 12v yet be able to run at 25% speed but now that you explained it, it makes perfect sense, thanks!
Thanks
I was just talking about PWM with a colleague. Great explanation!!
Thanks for watching!
Can't wait to watch, glad you keep making such nice content !
Atilolzz B
ESP/LTD love.
TheFatApache thought that was a Les Paul but went back and checked
it is a ESP/LTD
I didn't know he played guitar though
he also have that wine red lp custom + a marshall halfstack
Your guitar comparison was on point!
Thanks for the wonderful explanation! This is why I watch your content.
As always love the science. Thanks for the vid.
Thanks, Greg! Love the info!
Great video, thanks for the explanation!
Love the guitar! What brand/model is it?
Nice guitar dude. You think you would do more videos on instruments, amps, or pedals. I would love to see a Science Studio take on these
Excellent video. I literally just learned about PWM at university, but this still taught me a thing or two.
Yeah bro! Super simple..! Thanks for the explanation! ❤️
BTW what’s your chair...it looks super nice!
Great video as always Greg :)..Greetings from Italy
I feel proud for learning... Arigato Sensei!
Surprised a video about fans is interesting.
Great video, just switched my cpu cooler over to PWM in bios. You make it fun to learn as well!
Thanks for watching!
What a beautiful Eclipse :)
That was a great explanation. Thanks.
Although I already knew the info Greg, really liked the whiteboard stuff. More please ☺️
Gotta love seeing that gorgeous guitar.
beautiful ESP. i'm ready for some shred vids
Holy smokes.... You actually made a good video. Nice work.
So just one week after presenting my PWM circuit as my final project and getting a bad score, you upload this video...
Where u live at man? Love the way you explain things and wish I could intern or work for you lol
Thanks for educating.
love an engineer explaing things . !!
lucas rem ah um dude i study at iit bombay search it in google about the collage
Lucas rem im from india
thank you for making this
I'm using a retro Cooler Master ATC 200 case so the I definitely appreciate the PWM technology. Since my case only allows 80mm fans, letting them sync to my bios' fan curve to modulate their rpms makes it much nicer when I'm just casually using my desktop.
Perfect explanation, thanks! Personally I decided to go for the Silent Wings 3 DC fans though, as I found them for half the price of the PWM. Would’ve preferred the PWM, but I can’t go past a deal lol.
The higher the ON TIME of a signal, the higher the UP TIME of the fan will be. The fan basically stops when the N TIME[ data bit = 1, on time] ends and tries to stop due to next bit being 0 i.e. OFF TIME but, the motion keeps it going and as the PWM waveform switches states in nanosecond scale, the state change of fans[ off-on-off-on-...] is NOT visible to us human eyes. GG, Electronics student here, the first tech channel I've seen who at least knows what he is dealing with and let's the community know it. A big thank you Greg sir, good wishes from India. :)
*Science Studio, hence justified!
Damn that's one sexy guitar
Great job breaking that down.
Great video
Someone wants to show off his new "Ben" guitar...? Awesome piece, props to that special someone 😉
love the animations
I love your visual aid. I'm trying to start a visual aid series to explain different things in the computer world. Mind if I borrow that visual aid?
Nice eclipse man!
thx for explaining Greg-san 😁👍
nice guitar there!
In addition, in the LED age and lighted fans, running lighted fans in varying dc mode, lights will change brightness accordingly. In pwm 12v are always there and lights will stay bright
Any recommendations on fan hubs to be able to control your fans in say a custom built desk pc?
Nice ESP/LTD!
Videos about guitars would be great as well.. :D
But greg, would it be possible to add somekind of resistor ( between the fan connector and mobo pins) that reduces the output for the fan to decrease the RPM? We can regulate lightbulbs doing something similar so why not fans?
One could potentially buy a set of fans and test them with a fancy science-lab powersupply to answer the question that is: how much voltage do i need to apply for the best airflow/noise ratio?
This video showed up in my subscription feed twice
Beautiful guitar. I don’t have any Les Paul shape guitars, only superstrat style (Ibanez RG320 from 2001, and a squier strat that I’ve modified).
You didn't explain WHY PWM control is better than DC control. DC fans can be adjusted almost as well as PWM fans, the low speed operation is just a minor bonus that PWM control gets, but it's absolutely not why they are used, and better.
The reason PWM is better than DC control for fans is all in the power supply.
Providing variable power to a fan by varing it's DC voltage requires another power supply, similar to a Vcore VRM.. a hell of alot simpler, it's typically a simple buck converter, but this is inherently less efficient than simply giving the fan 12V and the fan doing the work of regulating it's power draw (which is either on or off so no wasted power).
This is why your PWM motherboard headers can easily take 2A current, if not more (the simply connect straight through to the 12V of the main PSU), but most DC controlled headers can only provide up to 1A safely. Above that and the buck converter built into the board will overheat, especially in the 50-80% region.
This is the same principle as any mosfet consuming power - it consumes most power when switching between on and off, either fully on or fully off it doesn't consume much power at all, (and why your CPU draws almost no power when not switching) - but when switching has it's highest value of current*impedance, meaning the I*I*R power losses are highest. The mosfets in the buck converter will be in this state most when providing between 50-80% of their input voltage of 12V. Some well designed fan power supplies will sink the most power at full load, and be more efficient at lower voltages.
Either way, with PWM all of this is negated, other than the much simpler and more efficient mosfet in the fan hub itself with far lower switching frequency (it only needs to switch typically once per 1/4 fan revolution if at all, so about 100 Hz) which is much less than a typical buck converter mosfet switching frequency in the DC-DC converter, which switch in the 300 KHz range. This is the only way to do DC to DC for power electronics, it's still a switched mode power supply and so ~85% efficient, but chopping it to AC, and back to DC is the only way. Using a linear step-down like a variable resistor or those resistors you can put on fan cables would be more like 50% efficient, so it has to contain switching mosfets, capacitors and inductors - again not needed for PWM, other than a much simpler more power efficient design that switches only when the fan needs to - for powering the coil for part of it's cycle.
Sharing a PWM signal to control 10 PWM fans is easy, anyone with a soldering iron can make the connections, assuming powerful fans or water pumps etc.. - 5A draw at 12V, no problem, and nothing else needed other than the PWM signal from the CPU fan header, and 60W on the 12V rail of your main PSU (and routing 5A through the board or wires, however they are connected, which is no issue).
Controlling 10 DC fans from a DC signal that can only provide 1A max (so can only be used as a signal not power supply), or using a PWM signal to modulate a buck converter to make 5-12V DC up to 60W - the only way to control those fans - means an actual 70W power supply that costs as much as 70W DC-DC converters cost, and dissipating 10W of heat from the extra power supply, and routing 6A to it from your PSU).
This is why PWM control is better than DC control, and why if you deck out your system with fans, only a few can be DC controlled if your motherboard does DC control at all.
Also I believe the 4 pin fans have a BLDC motor with a complete ESC inside. The PWM signal from the mobo is not used for chopping the 12V, but only to tell the ESC chip at what speed to commutate the fan motor. The actual PWM from the ESC will be completely different from the one the mobo sends (depends on the properties of the motor eg: no of poles etc.)
mashfaqm yup that's true.
For those who didn't know, "real" PWM for e.g. industrial motors etc has PWM on the actual power rail..
I'm not sure why but if you try to give a fan PWM on its 12v power rail they don't play niceley.. So they do this instead, with the PWM being only a signal and the actual power switching done by the additional circuitry you mention in the brushless fan hub.
Cool n quiet also affects my 3 pin case fans rpm. If i don't have it on, then they go max speed.
what circuit do you need to control the duty cycle? (i am powering from 9v on pref board)
Ok question, if im wanting to connect 3 pwm fans of different sizes, a 200mm and 2 80mm, 200 being intake and 80's being exhaust, but only have 1 pwm header on mobo, can i use a pwm fan hub and safely run all the fans? If im understanding right pwm % based, so the 80mm will run at 75% of its rpms and the 200 would do the same? But theyd all run the same % but not same rpm since its a single header?
Let's see you play that Axe!
good boi, you won a damn cookie
Guitar vid? Looks like an LTD or ESP. Do you play?
Would love to hear some tones out of that ESP.
Nice video. Some fans are already so silent you won't hear them even in DC mode much, especially with low TDP CPUs. Still don't see the killer advantage in PWM apart from extremely low RPMs (versus not running at all).
ESP LTD EC...256?
Edit: ooo the 256 has the 12 fret model inlay, the Ec-1000 doesn't. Great sounding guitar nonetheless.
most of us here knew that already , but tutorials like this can help newb a lot 👍👍👍👍
What's your opinion of an i7 3770 with a descent dedicated graphics card for a budget gamer?
If I set my fans to spin at their lowest possible speed, will they be generating enough airflow or are they just overcoming internal friction and maybe just stirring up the air instead of pushing air through?
so basicly, every fan has PWM if you connect it to a 4 pin on the motherboard?
regardless of the fan if it is a cheaper or more expensive one?
Hi.
I want to test PWM fan with power supply, (+ and gnd), is it possible? if it is, how I connect two pins to the four pins of the PWM?
Thanks!
Can I please have a link to your desktop wallpaper?
Since you like Be Quiet Fans (I love them) is there a reason to buy the 3 pin variants over the 4 pin PWM? On New Egg the 3 pin and 4 pin PWM ones are always the same price (unless there is a special sale)
With those fans I can't see a reason to ever buy the 3 pin variant unless its a special sale.
What pair of headphones are in the background?
if theres a fan option in our bios AUTO/PWM, which one better ? and whats the different..
Wish there was a love button instead of a like button.
3 pin version of same fan can be better as the 4 pin at same speed. Btw, I can recommend the Noiseblocker NB-eLoop B12-1 and B12-2, which I use since 4 years. The B12-PS version is the pwm version, but the 3 pin versions are somewhat better.
So should I set my pc fans into Pwm or DC which is better
Analogy:
It's like a kids carousel. The adult puts energy to push it around in a circle, with the carousel spinning at a constant RPM with the adult pushing every so often to overcome friction losses... to spin faster the adult may push/pull just as hard but do it more often.
Dayum dat LTD guitar
Which software can controls the duty cycle?
I'm more of a fender man myself but that guitar was very nice
Can you do itx one fan header mobo soultion for tge extra fans that can be controlled via bios or software instead of traditional molex fan adaptors. as an example. I have gigabyte itx b350 with only 1 system fan header. I am using bitfenxi prodigy itx. I have 230mm bitfenix specter pro as intake attached to the mobo. While having two 120mm regular corsair fans as exaust on top. And finally cosair AF120mm fan at back at exhaust. My question. Can i connect all fans on single fan header without the risk of frying the fan header on mobo cause of too much amp. And is there is any way to control the extra fans via software or bios with only single extra fan header on the mobo. Thank you
Does your mod mat overclock to 5GHz?
Keep it up S.S
Ah science... Good stuff
So, you have a use for that Marshall stack... Favorite Metal band?
What is dc mode? Is it different with pwm?
Eclipse is love
that is a nice guitar
That’s so funny, we are using PWMs for our robot using arduinos in one of my engineering classes
Love your videos bro.
Thanks for watching.
Science Studio you're very welcome man. Thanks to you for posting the best tech videos.
Your pc wallpaper?
not sure if anyone mentioned this before but you look like the actor (Joseph Fiennes) from enemy at the gate haha
you should make a video or two on your guitars. I'd watch that tbh.
he has a video on him jamming on his guitar but its his les paul custom not the ltd he has in this video. to my knowledge he doesnt have any other guitar videos
Hello people!
I wanna ask you guys something. I wanna hook up a server fan, which is about 6000 RPM and draws about 3A of current, to my desktop PC. So my question is; can I draw the power directly from the power supply, where there is no shortage of current and no risk of damaging the motherboard traces due to excessive amount of power drawn by those fans, and connect the PWM and RPM wires to the designated pins on the motherboard?
Has any of you ever done such thing before? Am I missing anything? Please let me know.
Thank you!
Hey good video
I'm getting bad flashbacks from my microprocessors 2 course from last semester. That shit literally gave me ptsd
pwm is also on keyboards lights and monitors backlights, there is where it makes the most damage, creating flicker.
most monitors are flicker free now, its in the spec sheet. keyboard however is still in the dark ages and dont state it.
More guitar videos!
I remember seeing someone else saying how they were thinking of some pc question and you uploaded a video about it... I'll be dammed if that didn't just happen to me. Just ordered my first pwm control and fans, finally ditching molex. Get outta my head Greg lol
I have Deep Cool fans in my case. The box says that they are PWM but they only have a three pin plug for each fan. Is the packaging wrong?
Very likely.. No fan on the market has PWM with three wires, it's possible if they left out the tac signal, but as the tac signal is free to route out of the fan, and the PWM control electronics costs money, there are only DC fans with tac (speed) signal, 12V and ground (3 pin) and PWM fans with 3 + pwm signal for 4 pin.
Basically 3 pin fans can't be controlled with a 4 pin header made for PWM only control. If you do plug them into a 4 pin header they'll just run at 100%, as they are given 12V instead of varying their voltage. It's perfectly OK to do, and you'll be able to read it's speed, it just wont be speed controllable and will be at full speed all the time.
If you use a fan hub, and it's the kind that connects to only one 4 pin motherboard header to drive e.g. 8 fans, then the PWM output from the 4 pin header (the 4th pin) is sent to all fans to control all of their speeds (providing they are PWM fans). On the tac signal into the motherboard 3rd pin, only one of the fans will have it's tac signal routed, and so it'll only measure the RPM of that fan.
If it's a fan controller with USB, and has as many measuring sensors for the tac wires as there are fans, and can give an independant 4th pin PWM signal to each fan.. well it can provide PWM control to each fan and read their speeds, but again if you connect a 3 pin fan to the 4 pin PWM header.. it can still measure the RPM of the fan, but it will have no PWM control.
If you want to control a 3 pin fans speed you need to vary their voltage= (12V pin for PWM control) to a lower voltage, i.e. DC control. DC control means having a DC-DC converter, which becomes just like a mini Vcore VRM, a switched mode power supply on the board, and can overheat when supplying too much power say over 1-2A. This is the only way 3 pin fans can have their speed controlled, and they also can control 4 pin fans - they too will run perfectly fine and slower if you lower the voltage on their power pin.. So, why not just use DC control if it controls DC(3 pin) and PWM(4 pin) fans? DC are cheaper fans to buy, but more expensive to have circuitry to drive. Lookup things like the "Zalman fan mate 2" - only 2 fans controllable for £15, whereas a PWM splitter costs only as much as the wires it's made of, and an 8 fan DC fan controller would be an expensive power supply that no-one makes for that reason.
Some motherboard "4 pin" fan headers are actually just 3 pin DC control headers (typically say no more than 1A), with an extra pin for show, almost always the system 1-3 fans (this is the case on my 6 year old ASUS M5A99FX PRO R2.0)
Almost every CPU header 4 pin is an actual PWM header, same with "power fan" or "CPU-OPT", and can give anything up to 2-5A, and they don't need any power circuitry, just a straight through connection to the power supply's 12V rail for power. Most modern 4pin fan headers are like this.
.... AAAnd then there's the last type, which may have been what was on your Rog fan hub, but mainly on very good motherboards - a 4 pin header capable of detecting whether it's a 4 pin PWM fan connected, giving the fan PWM control on the 4th pin and 12v on the power wire, OR detecting only 3 wires connected, and giving it DC control by varying the voltage on the power wire, but it would only be able to control so many DC fans for the reasons mentioned.
However, you can only have so many DC controlled fans in your system, limited by whatever they're being powered by, i.e. the DC-DC power supply in your fan hub, or motherboard, but with PWM you can put as many as you like in, carrying 12v at 5A straight through to a fan is alot easier than converting 12V to 9V at 2A.
Anyway that should describe what options you have for fans, and why if you want lots of them, you need PWM. A few controlled by motherboard DC headers is fine, but if you want more, or power for pumps, or quadrupling up fans from the same header, or driving 12 from the 12v line of a molex connector controlled by the CPU headers 4th pin PWM signal... you need PWM.
I knows that a massive response, but I had to work this out for myself recently after I was finding out why the hell my motherboard had these fake "4 pin" headers with only 1 A current capability (that should have just been 3 pin headers), and I was decking out my system with DC fans from an old system.
Also.. you can do PWM the "old fashioned" way, and provide a PWM signal on the actual power line (this is how PWM works for other motors) but fans don't play nicely with this at all, not sure why, but that's how they are as they are.. with special circuitry in the fan to do slightly more complicated switching (compared to the usual PWM on the power line) depending on which coil needs to be switched at which time. The PWM signal just turns into a signal for the fan to read rather than an actual powered duty cycle like industrial motors.
What about flx fans?
How about making a cover in your next video Greg ? :P
One more thing added to my knowledge ths mane