WEBVTT

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how does your computer put on such a fantastic light show with all those LEDs

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how do the lights fade and change colors is there a legion of pixies with an

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amazing array of dimmer switches coordinated precisely so that your

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friends are impressed with your RGB lighting well the reality is a bit less

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Fantastical but with the recent unionization of pixies we have the much

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more practical pulse width modulation so

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what is pulse width modulation pwm varies the perceived power going to an

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electronic device by very quickly turning the power on and off the

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perceived output is changed by varying the duty cycle now the duty cycle isn't

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the time it takes your dog to spin around before going about its business

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but instead how long the signal is turned on versus turned off this means

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with the duty cycle of 50% the signal is turned on half the time and off the

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other half whereas a duty cycle of 100%

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means the signal is always on an important part of the duty cycle is the

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switching frequency or how fast the signal is turned on and off for instance

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turning an LED on for a second and then off for a second would be a duty cycle

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of 50% but the LED won't be half as

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bright it'll just be annoying to make

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the LED appear dimmer the onoff switching has to be faster than the

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flicker Fusion rate or how quickly a

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light has to turn on and off to be perceived by the brain as being

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continuously on in humans the flicker Fusion rate is around 18 times per

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second typically LEDs control by pwm will be switched on and off over a 100

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times per second or 100 Hertz by using a duty cycle of 25% at 100 HZ it means

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that the LED would be turned on and off 100 times per second but the duration of

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each on cycle is only a quarter of the time making the LED appear 25% as bright

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and and as you probably know pwm is also useful for quiet and efficient PC

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cooling older fans controlled from the motherboard had very poor speed control

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meaning that the fans would run much faster and louder than they actually

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needed to be at that point in time pwm fans however allow for the motherboard

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to easily control the fan speed giving low quiet fan speeds when just browsing

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the web to gale force wins when you're

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playing crisis so can we dim a light or change a fan Speed without using pwm

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well older systems might use DC voltage control this works by changing the

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resistance in a circuit the more resistance the less power transmitted to

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the fan or light since there is no

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switching DC control has the advantage of smoother power delivery but they

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often don't offer the same range of speeds that a pwm fan does not to

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mention that any power that isn't being used gets wasted as heat which is why

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old dimmer switches use the same amount of power no matter how much light they

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made it has been said that pwm monitors can cause eye strain from the constant

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flickering although makers of DC controlled monitors seem to pretty much

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be the only ones that are saying this so

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trust them if you want beyond changing how much power is going to something pwm

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can be used to transmit data between two devices where pulses of different

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lengths represent the data being transferred this is how your TV remote

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switches channels and how data is transmitted from cell towers to your

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phone pwm is also used in some audio amplifiers making them extremely

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efficient the typical efficiency of a non pwm amplifier is between 25% and 50%

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while a pwm amp can reach efficiencies of

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99% the cool operation and high efficiency makes these amplifiers

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like this video like it if you just like this video dislike it get subscribed let

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us know in the comments down below if there's other stuff you'd like us to cover and check out uh this video which

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is Dennis's third favorite Channel super

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fun not his first not his second very

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specifically his third and there's very good reasons for that