low pass filter design

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p72

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Hi All,
I have attached circuit for Low Pass Filter at cut-off frequency 60Hz.
My input is 240VAC, 60Hz for this filter. My goal is to block all AC signal at the output of the filter (means I am looking for DC.).
Two questions: -
(1.) If I use attached circuit, can I get DC as an output of this filter?
(2.) What will happened to 240Vac voltage? Will voltage (240Vac) stay same after output of this filter? (If yes, how can make it to ground?)

Thank you,
p72

 

what is your application! will you be supplying something with the acquired DC?
 

trying to bypass AC at all. Like capacitor can block the DC, do we have anything that can block AC?
 

Good day
1- you will not get AC from the output of this filter
2-the amplitude of the 240 VAC will decrease to 0.707 of its original amplitude at the cut off frequency .
getting DC from AC signal usually involve rectifying then passing through low pass filter
if you have something specific about your signal , more details will help us to asist
Regards
 


Hi p72
not absolutely sure what you're trying to do, but this filter will certainly not remove all the 60Hz a.c.

>means I am looking for DC.
Am I right in thinking you have a problem with the 240V ac mains supply such that it has a d.c. potential on it (i.e. a fault condition) ?

If so then you could try this circuit attached; T1 will provide a balanced termination to the mains and give zero volts a.c. at the centre tap point. If you then measure from the center tap to earth with a d.c. voltmeter then you will see whether a d.c potential exists on the mains supply.
(NOTE: make sure the transformer you use will handle 240V ac, & you don't need to connect anything to the secondary)
 
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It sounds like you want a DC output from your AC input. In that case you can use a bridge rectifier to give a DC output. If you use a large smoothing capacitor at the output you will get a DC supply with low ripple. The exact amount will depend on the capacitance. The DC voltage at the output will be about 1.41 times the input AC RMS voltage.

If you had something else in mind, then please describe further.

Hope this helps.
Tahmid.
 

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