I don't understand if you use both capacitors in Pi filter to calculate cut off frequency or just the last one connected towards the load.
What capacitance does the coil see? Think of the loop from the coil's point of view. Are the two capacitors in series or parallel?Example formula: Ctot = C1 + C2
You use both capacitors AND the load impedance AND the source impedance. They all make a difference. The formula given is for an LC section assuming the other capacitor is absent or does not significantly affect the result, and that the load and source impedances have no effect.I don't understand if you use both capacitors in Pi filter to calculate cut off frequency or just the last one connected towards the load.
I attached the filter I'm working with,You use both capacitors AND the load impedance AND the source impedance. They all make a difference. The formula given is for an LC section assuming the other capacitor is absent or does not significantly affect the result, and that the load and source impedances have no effect.
Do you have an example filter that you are working with or are you trying to design one for some purpose?
I see, I'm very new to designing filters. I knew only that around 50-60Hz is the noise from my source voltage, so I should have a lowpass filter to filter out as much as I can. I'll have to watch some videos to understand this better. Thanks for your guys help.I had a suspicion that it was for a power line filter at 50Hz. Low and behold there is a resonance peak at 50 Hz. What this is doing is enhancing the noise. It seems you threw this thing together without setting out any requirements and without doing any design.
View attachment 288674
Some other points:
Did you compute the reactance of each component at your frequency of interest, 50 Hz?
- You cannot ignore the source impedance, but you know that for a typical power supply it will be small. I chose 200 mΩ
- You cannot ignore the load impedance, but you have to bound it as a minimum.
- C1 & C2 cannot have the same value.
XL1 = 31.42 Ω
XC1 = XC2 = (1/31.42) = 0.318 Ω
That's OK we all had to start somewhere. I'm not sure videos is the way to go about it, however. It is unstructured and difficult to assimilate. I did not come to my present state of knowledge overnight. It took over half a century. If 50-60 Hz. is your problem you might want to consider a notch filter, or other ways to eliminate the source of the noise.I see, I'm very new to designing filters. I knew only that around 50-60Hz is the noise from my source voltage, so I should have a lowpass filter to filter out as much as I can. I'll have to watch some videos to understand this better. Thanks for your guys help.
It depends what you are using it for, which i dont think you said yet?I don't understand if you use both capacitors in Pi filter to calculate cut off frequency or just the last one connected towards the load.