Tip to figure out noise problems in a pcb.

Hello people. I am very frustrated right now. I designed a PCB to convert the anaolg signal provided by a image sensor into digital impulses.
In my first revision of the board I made several mistakes in Altium (I place the footprints mirrored) but in the end, I was able to run the board without too much problems and it is working properly. But now I made a new revision of my PCB and little swing in the image is displayed when the sensor is running. it is like a electric noise generated in the pcb but I cant figure out where it is the origin...because the new rev the same layout and the same components that the previous revision. The only change that I did was place the components in the right way (no mirrored). Any tip to figure out the origin of noise problems?

Thanks

flote21 said:

...I made a new revision of my PCB and little swing in the image is displayed when the sensor is running. it is like a electric noise generated in the pcb but I cant figure out where it is the origin...Thanks

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Based on observed behavior of such noise compared to the known horizontal video scan rate, can you determine what is its dominant frequency ?

This way, you can take the focus on the right direction to find the cause of failure.



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That it is my problem. I cant know wich is the freq of the swing.... I think that the origin of my noise can be the ADC. I observed that there is a input in the ADC which is very sesnsible to the noise. It is the ref voltage. To filter out this ref volt i placed a R-C filter in the pin of the ADC (100ohm and 10uF). After several tests, I discovered that if I change the vallue of the R in the filter R-C the swing is bigger. But The vaule with less swing is 100 ohm. The previos version of my design has also the same value of R and there is not swing...IT is very strange..