Hi,

My first circuit is using some relays and the second is made with BC457 and leds.
I noticed that when relays are on some interferences can light on leds on the 2nd circuit !

I saw on internet "Low pass Filter" and "High pass filter"

I would like to know do i have to used them ? and how to calculate the value (R and C) ?

Regards

 

Do you have diodes across the relay coils to suppress the inductive transients?

 

My first circuit is using some relays and the second is made with BC457 and leds. I noticed that when relays are on some interferences can light on leds on the 2nd circuit !

I saw on internet "Low pass Filter" and "High pass filter" I would like to know do i have to used them ? and how to calculate the value (R and C) ?

Before jumping to conclusions about needing filters to solve your problem, let's first try to figure out where the problem is coming from. First step: post a complete, accurate schematic diagram of your circuits showing all components and all connections.

Then we can begin.