One of the more enjoyable uploads though. The visual and practical stuff with simulators and graphs and oscilloscope traces teaches concepts a lot better than textbooks.
I think there's a small problem in the video, it's all black around 30:50 to 31:28.
All this PWM filter stuff is a bit meh. It would look far more impressive to attach a stepper motor to the ten turn pot and control the stepper motor from the micro
I think there's a small problem in the video, it's all black around 30:50 to 31:28.
Yes, there's a superfluous clip from 30:53 to 31:28 which repeats the audio from 30:18 to 30:53 with blank video.
All this PWM filter stuff is a bit meh. It would look far more impressive to attach a stepper motor to the ten turn pot and control the stepper motor from the micro
Just like on those expensive Hi-Fi's where people want to see the knob spin at their command from the chair huh?
Dave.
Dave, a small request...
Can you use the rotary encoders method for the project? Rotary encoders always gives me a hard time.
I am wondering about few thing, regarding to this episode. Is there any method to make integral from pwm signal really quick, for example let's get the situation where whole power supply is build around micro and hysteresis for current limiter is in software, then we need really quick reaction.
I am wondering about few thing, regarding to this episode. Is there any method to make integral from pwm signal really quick, for example let's get the situation where whole power supply is build around micro and hysteresis for current limiter is in software, then we need really quick reaction.
Also I wondering about how they measure current in all of those cheap-china powersupplys where they have 3 terminals and only one 3-4 digits amp meter and the current may flow in 3 "path" (plus2ground, minus2ground and plus2minus).
For those who like math, the dual stage RC filter has this transfer function :
And present this impedance to the input:
(it's all from a 'back of the envelope' attempt, so I might have made a mistake but it "looks" right)
For those who like math...
Dave, a small request...
Can you use the rotary encoders method for the project? Rotary encoders always gives me a hard time.
Yep, I'll be using them.
Dave.
I'm pretty sure the filter was a cascaded 2nd-order RC low pass with a transfer function:
This doesn't look right. It looks just like you multiplied the two transfer function of each stage.
The RC filter has this transfer function :
But only if the loading impedance at the output if negligible. Which is the case for the second stage (because feeding an opamp), but not for the first stage which is loaded by the second stage and introduces another term.
PS: Nice analogy I also don't do math just for the sake of it, but I found myself having to compute a RC filter having a specific impedance while in a train with nothing else than a paper and pencil and I just tought I'd share this because I find it useful to sometime being able to go back to this. (Even tough when I learned that at uni I wasn't convinced of the usefulness
See attached pic for circuit, just to be sure we're on the correct page. For simplicity of analysis, we'll denote R1/C1 as 1st-stage components and R2/C2 as 2nd-stage.
So it's clear that the stages are impedance matched. Of course, this assumes that the output impedance of the uC pin providing the PWM signal and input impedance of the non-inverting input of the buffer are very small and very large, respectively (which is a reasonable assumption). QED.
And btw, I LOVE this codecogs instant online latex business! Thanks for the indirect link!!