RC Low Pass Filters (make an analog value from PWM)

[@ericying]

12 years later KZbin suggested your video and finally I got it! Your side-by-side of a PWM signal with a sound wave on 9:58 made all the difference. The term "filter" confused me and probably many newbies into searching for this mythical "low-frequency" in a PWM signal, thinking it's a defined number. Thanks for making this!

[@mustafaturkoglu4459]

you know the video gonna be good when it's only only pen and paper.

[@johnclavis]

Thank you for an extremely informative video. I'm trying to control a trinket with an Arduino by having the trinket read different PWM values as different analog input values so that I can tell the trinket to switch between various modes. It looks like I'm going to have to use some kind of low pass filter in order to get the trinket to receive and recognize distinct analog values. Of course, I don't want it to take more than a tenth of a second or so for the value to stabilize, so that I can switch trinket modes relatively quickly. Your video will help me with this problem. Thanks again.

[@dantheman1998]

I have a motor control thats looking for a analog 0-7v for speed control. would I need a really complex low pass because what the motor controler is looking for in voltage is a load Or will a simple one work because its not really a load?

[@rich1051414]

Put a 4.7 ohm 15 watt power resistor in series with the PWM power, then after that, a 470k and a 10mF 15v capacitor in parallel to ground. Where the two resistors connect will have the averaged analog DC voltage. The 470k resistor to ground isn't totally necessary, but without it, the voltage will rise to 7v under no load, and the capacitor will never discharge. It's inefficient but the simplest way to achieve what you are looking for. It's really ineffecient if running near 100% duty cycle, but 50% or lower it shouldn't waste that much power generating heat.

[@quicknuclearscience]

Thanks, more are planned for the future.

[@robertsoderman5742]

Awesome video!

[@MrMinimalSWN]

Hey, can you clarify some questions about 2 differant Cutoff Frequencies for AM Signal? When a 100Hz Carier Sinewave is modulated with a 200KHz Squarewave: It has aswell positive bumps as negative right? And if I filter at 500Hz will it have less output as a 20KHz Lowpass? Thanks in advance, greets.

[@gabrielgiacomini]

Hey, first of all thanks for the video! I was hoping to find part 2 but couldn't see it anywhere. My objective is to convert arduino PWM to analog 0-5V DC, so I can use it to control some CV-controlled parameters of my analog synthesisers. I imagine what I want to do is simpler since I don't need the output to be modulated in high frequency as you do, but I'm a dummy so I would highly appreciate if you would give me any further lead :) Thanks

[@quicknuclearscience]

I'm sorry for not having made part 2 yet, it has been busy recently and I am forgetful, but don't worry it will come eventually. A simple low pass filter with an absurdly low cutoff frequency like .1 or .01 hZ would do, or if you want a bit more exact control an R2R ladder would also work. But that is more complicated and no reason to use one over a simple PWM low pass filter setup unless you need the output to be exact.

[@lenskimono2954]

2016 wants part 2. Great video!

[@irtazaanwar2144]

2017 wants part 2

[@enigma7070]

2018 wants part 2

[@pedroazevedo5300]

2019 wants part 2

[@quicknuclearscience]

Whats wrong with what I'm saying?

[@quicknuclearscience]

Whats wrong?

[@zaytiggy5188]

The way you depict amplitude modulation is incorrect. In amplitude modulation, the amplitude of the high frequency modulating signal (usually a sinusoid) is varied in line with the amplitude of the low frequency message signal. The resulting AM signal varies periodically about zero. In your drawing you have the opposite. Your carrier signal varies periodically about your message signal.

[@NikolaosLedZeppelin]

nope! you describe all wrong.