Re: Low.pass filter

Thank you for your reply, but as I am using the original filter/amplifier
design it would be really time consuming to modify it to another type of
filter. I just need to get to understand what have been used
 in the original design. The original design is here:
https://imgur.com/a/MzSs2

If you would be able to point me to the right direction I'd be really
grateful.

2018-02-01 11:38 GMT+01:00 salsero <[email protected]>:

>
> Hi Damian,
>
> Did you try a twin-T notch filter? An RC low pass filter is not really
> that sharp. May these articles will help you:
>
> http://www.g3ynh.info/circuits/Bob_Batey/LB-5.pdf
> http://fourier.eng.hmc.edu/e84/lectures/ActiveFilters/node4.html
>
> Hope this helps a bit,
>
> Leo.
>
>
>
>
>
> Damián Filo schreef op 2018-01-31 16:58:
>
>> Hello everybody.
>>
>> As I am finishing up my project of customizing EEG-SMT I encountered
>> some things I can't seem to understand about the OpenEEG. One of those
>> things is the 3rd order besselworth filter which I cannot successfully
>> reverse-engineer in several Bessel filter calculators. Every time when
>> I enter the provided values of cutoff frequency, order... I get really
>> different values of the parts used. It is really important to me,  I'd
>> like to set it to 49Hz cutoff because of european electric network of
>> 50Hz. That's why I get too much 50Hz ripple. I will share the
>> schematics, board and electrode designs, but at first I need to
>> understand the filter. Is there someone, who will be able to explain
>> the value selection and formulas used for this filter? I'd be really
>> thankful. I spent hours maybe days figuring it out, but I can't seem
>> to understand it. I used multiple calculators, but this one looks the
>> best: http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html [1]
>>
>> Thank you in advance.
>>
>> --
>>
>> Damián Filo
>>
>> Links:
>> ------
>> [1] http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html
>>
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>
>
>
>
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-- 
Damián Filo

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