Gadgetory

P W M stands for pulse width modulation but this doesn't really tell the layman much at all I mean not like vrm let's say which stands for voltage regulator module pretty self-explanatory in that case the RM is regulate voltage delivered to a processor by stepping it down to a much safer level but pulse width modulation is a characteristic of certain fans in the PC realm there are other applications that will stick to that one because that's probably what you've heard it first so what does it mean and why should you look for it in essence pulse width modulation is a method used for imitating analog wave patterns with a digital interface and we can depict digital signals graphically with lines representing either on or off States DC voltage is depicted as a straight line and it's y-intercept indicates the input voltage in the computer realm DC fans typically boast three pin fan headers the first cable records the fans are p.m. the second sends the voltage typically 12 or 5 volts and the third acts as ground these fans are typically a bit cheaper than their PWM counterparts and are less versatile from an RPM standpoint so voltage fed down the second wire is varied to control fan speeds on these three pin fans and that's according to the user's calibration but minimum voltage is usually quite high meaning that the minimum rpm for the fan won't be very low which means that they won't run super quiet in most cases if voltage drops below this minimum threshold then the fan won't spin at all but pulse width fans are a different story rather than varying voltage down the second line voltage is fixed with the fourth pin active so this fourth pin actually control signal duration or the pulse width and you see now where the name comes into play and the longer the pulse from this wire or the larger the gaps in the pulses the lower the duty cycle which essentially affects the RPM the lower the duty cycle the lower the RPM of the fan for instance this would represent a twenty five percent duty cycle when the source voltage is fixed at 12 volts but only in the on state twenty-five percent of the time a duty cycle of 100 percent is equivalent to the fan running at its maximum input voltage will say 12 volts for this example and a duty cycle of zero percent will stop the fan completely an important note here input voltage is constantly applied to these fans and the pulse width modulator acts the switch so longer the switch is closed and what circuits closed the longer voltage is applied to turn the fan on you can think of PWM in another way too strumming a guitar so if I pluck one string every five seconds I'll hear the sound spike and then attenuate it starts loud and then tapers off the amplitude is similar to the RPM of the fans so if you hit the fan with 12 volts on shorter intervals or in this case if you strum the string let's say once every one second instead of five then the medium has less time to attenuate the amplitude stays higher overall and this of course translates to the fan as a higher rpm we can see this relation graphically if we match up fan rpm and voltage a first time pulse with modulation tuned to a 50% duty cycle looks something like this with our peak voltage of 12 volts and in the dependent variable that's rotations per minute depicted here so when PWM mode is active the corresponding fan will literally turn on and off in essence by varying degrees to maintain the desired rpm that's why we can achieve such low rpms with these fans it just occurs so quickly that we don't see or hear it happening and do keep in mind that these values and recoveries will vary from fan to fan so in short PWM is a better alternative to DC counterparts four pins are better than three in this case you can achieve significantly lower rpms thanks to untouched voltage levels which means quieter fan profiles overall and multiple fans can be synced up to the same PWM profile via fan hubs and splitters since a constant voltage is applied in these situations you can even plug for pin fans into three pin headers on your motherboard they'll just operate in DC mode see the best of both worlds in a worst case you don't have an extra 4 pin of your disposal they're more versatile efficient and ergonomic and should be strongly considered for your next case fans I've linked several reputable kits in the video description below my favorite are the silent wings 3 fans both the 120 mm and 140 ml variants they're extremely quiet a bit pricey but they look pretty good doing it at the same time and of course they've got to be PWM some of them are DC so watch out check to see if their 4 pin or three pin fans if you like this video but should let me know I guess one of thumbs up I appreciate it comes down for Diop so you click that red subscribe button if you haven't already you can even sponsor us if you really want to do that when we have live streams you're gonna start kick more than once a week from now on because it's an interesting way to communicate with all of you so stay tuned for those announcements on Twitter and elsewhere this is science studio thanks for learning with us