Selection of a resistor and capacitor for making filters in wearable devices?

Sensacell

Joined Jun 19, 2012
3,180
"Where is the best place to live?"

Not enough context to provide any meaningful answer.

What are you filtering?
Why are you filtering?
What are you trying to do?
 

Thread Starter

Hamas Ahmad

Joined Apr 12, 2022
13
the first combination is R=47k, C=68nF
The second Combination is R=680 and, C=4.7uF
Which one is best to filter 50Hz and why?
 

Papabravo

Joined Feb 24, 2006
20,133
the first combination is R=47k, C=68nF
The second Combination is R=680 and, C=4.7uF
Which one is best to filter 50Hz and why?
As you are no doubt aware the solutions are NOT unique. You cannot determine two component values from a single equation. Also you cannot determine an optimal (best) value without specifying something to optimize. The answer to your question is indeterminate.
 

crutschow

Joined Mar 14, 2008
32,043
If you want a tighter notch than can be obtained with a simple passive filter, than you can use an active filter with an op amp.

Why are you have a problem with 50Hz?
If it's interference from the mains, then you may just need better shielding of the circuit.
 

Thread Starter

Hamas Ahmad

Joined Apr 12, 2022
13
Your resistances and capacitances were orders of numbers wrong. I corrected them.
Here is an extremely simple 50Hz passive notch filter:

There are unlimited combinations of resistors and capacitors to filter a specific frequency in the circuit. For example, I am filtering 50Hz from the circuit. There are a lot of combinations of resistors and capacitors to filter out that frequency. If, I make two different circuits of 50hz filter with different combinations of resistors and capacitors. Theoretically, both circuits will remove 50hz frequency from the circuit. Practically, Is there any other effect on the circuit?
 

MrChips

Joined Oct 2, 2009
28,497
There are unlimited combinations of resistors and capacitors to filter a specific frequency in the circuit. For example, I am filtering 50Hz from the circuit. There are a lot of combinations of resistors and capacitors to filter out that frequency. If, I make two different circuits of 50hz filter with different combinations of resistors and capacitors. Theoretically, both circuits will remove 50hz frequency from the circuit. Practically, Is there any other effect on the circuit?
Pay attention to the source and load impedances.
 
Top