S4 vs rs4

[gdallas]

Randomly farting about on YouTube there and came across this. Was a good watch
Audi S4 v Audi RS4. Does Supercharging Rule? - /CHRIS HARRIS ON CARS - YouTube

Makes me want to pimp out my a4 do it does :-)
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[Dieseldoos]

Nice video! I want to put the S4 quad style exhausts on mine, I think it looks nicer, but £800+ for the quad milltek, and whatever the S4 exhaust valence trim is, the misses wont be happy!

[johndeere2130]

Great review, but why are the lights flickering on the S4?

[gdallas]

i noticed that too.... but strangely enough i noticed the same when i filmed my own cars led tail lights. As an electronics eng i can only assume its because the "brightness" is controlled by something called a pwm, pulse width modulator which basically is able to control the intensity of the LED by altering the pulse width of the digital signal controlling it. bit like increasing or decreasing a power signal frequency.

[eob]

i noticed that too.... but strangely enough i noticed the same when i filmed my own cars led tail lights. As an electronics eng i can only assume its because the "brightness" is controlled by something called a pwm, pulse width modulator which basically is able to control the intensity of the LED by altering the pulse width of the digital signal controlling it. bit like increasing or decreasing a power signal frequency.

Thats right, LEDs are basically switch on and off but so fast that the human cannot detect it so we see it as constant light.
A digital camera working at around 24 frames per second means that some of the frames capture the LED on and some capture it off so we see it as flickering.
Search You Tube for the effect it has on an aircraft propeller:
digital camera effect aircraft prop - YouTube
Bizzare.

[gdallas]

well almost. LEDs can be held "on" continuously. via a current limittting resisitor. but when you want to have control over its intensity a PWM is a common method for doing that. hell, i used the same phillosphy for controlling one of our downhole camera lights in a well 10000 feet subsea :-)

[johndeere2130]

But the led's on the RS4 dont flicker, and it looks like the fog lights on the Rear of the S4 that are flickering(as well as the drl's)

[Guest 2]

But the led's on the RS4 dont flicker, and it looks like the fog lights on the Rear of the S4 that are flickering(as well as the drl's)

As above its something to do with the camera and the output of the LEDs. If I were to take a video of my A6 braking they would pulsate when watching the video back even though they'd be solidly on outside of the camera.



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