Building a custom notch filter

[mallyajiggs]

Thanks..... that really solves my problem

btw i also needed a line filter that allows only 60 hz frequency...to be connected to the electrical socket. any idea which is a good 60 hz band pass filter ?
is it ok to go for a low band pass filter instead ?

 

[(*steve*)]

Well, a powerline filter (any filter) is never going to allow only a single frequency through. They will reduce the amplitude of them, and the question you need to ask yourself is "how much noise is acceptable?"

It really depends on what you want.

One option is to use a UPS that is either dual conversion, or is disconnected from the mains. The problem here is that it may generate more noise than you have on the mains -- but it will be independent noise.

 

[mallyajiggs]

ideally speaking here i would like to have a bandpass filter for 60 hz , i.e allow only the AC frequency

but i can settle for a low pass filter with max value of 100 -300 Hz

 

[Resqueline]

You just take the twin-T filters you have there and swap the caps for resistors & vice versa, using the same values already there.

 

[mallyajiggs]

oh i''ll do that , just wanted to know if it was worth buying any popular commercial one ? any recomendations ?

 

[Resqueline]

I'm not quite sure I understand what you're after, but the only commercial sub-100Hz filter I know about is a constant voltage (ferroresonant) transformer.
All other mains filters have a significantly higher cutoff frequency (10-100kHz?)

 

[mallyajiggs]

anyways.... i searched on the net.. and will use this EMI filter

http://mouser.com/ProductDetail/Sch...=sGAEpiMZZMt5zLV74dRd3SddQ0c4cd5xbrMAUiYESvE=

Its supposed to filter other noises .. so i guess will settle for this, thanks guys for all the help & support

 

[Resqueline]

That one will filter out common-mode noise over 100kHz, and short differential-mode noise to some degree (due to the capacitors).
You're welcome, glad if we were of any help. Hope you get the results you want.