The Ideal Filter?

[Ron Hubbard]

Not too long ago I bought a $900 biofeedback machine that I use in
conjunction with an old IBM Thinkpad laptop. But I found that I had to
use it in a cold, drafty, room that has no appliances connected to the
mains in order to avoid 60 Hz electrical noise that ruins the
brainwave tracings.

Does anyone know of a circuit or a commercial device that
would *completely* filter out 60 Hz ripple so I could plug my
laptop's adapter into it without fear of any degree of noise?

Thanks

Ron


--
"My life is a Testament to all the things I can do-- when I don't
listen to other people."

 

[Sylvain Munaut]

Not too long ago I bought a $900 biofeedback machine that I use in
conjunction with an old IBM Thinkpad laptop. But I found that I had to
use it in a cold, drafty, room that has no appliances connected to the
mains in order to avoid 60 Hz electrical noise that ruins the
brainwave tracings.

Does anyone know of a circuit or a commercial device that
would *completely* filter out 60 Hz ripple so I could plug my
laptop's adapter into it without fear of any degree of noise?

The noise comes from what ?

Radiated power from other apliance in the room ?
Or noise induced in the powerlines by other appliance ?

In the latter case, a off-line UPS will take the mail lines, convert it
to DC then convert it back to AC. So the AC you get out of it should
be clean.

However, not really sure that your problem lies there.


Sylvain

 

[colin]

"Ron Hubbard" <hubbard-ron@hotmail.com> wrote in message
news:2t1j7iF1querjU1@uni-berlin.de...

Not too long ago I bought a $900 biofeedback machine that I use in
conjunction with an old IBM Thinkpad laptop. But I found that I had to
use it in a cold, drafty, room that has no appliances connected to the
mains in order to avoid 60 Hz electrical noise that ruins the
brainwave tracings.

Does anyone know of a circuit or a commercial device that
would *completely* filter out 60 Hz ripple so I could plug my
laptop's adapter into it without fear of any degree of noise?

Thanks

Ron

I think what you need is a notch filter. You can make a simple notch filter
to reject 60hz using 2 parallel T networks. at the notch frequency one RC
path delays the signal by 90' the other CR path introduces a lead of 90' two
resistors sum them both and the result is total cancelation at the notch
frequency.

Colin =^.^=