2019-01-22, 01:33 AM
Thanks Sean,
My impression is that the noise is coming from the 12V side and from the buck converter itself. I found a paper on the Internet about that type of noise from a buck converter, and potential solutions from a circuit design point of view. When I changed out the converter for one that was encased in metal, then grounded it, a great deal of the noise disappeared. When I further filtered both 12 and 5v sides with clamp-on ferrites and grounded the RPI case and the buck converter, the noise reached a "livable" point. I've ordered a few common mode filters from China to see how much more difference they make.
In interesting thought to implement a conventional regulator after the buck converter, although if the noise truly is common mode, I would think that it would still make it through.
I guess I should find a scope with a high enough frequency range to do some real scientific testing... then again, perhaps I should put down the soldering iron and go sailing!
My impression is that the noise is coming from the 12V side and from the buck converter itself. I found a paper on the Internet about that type of noise from a buck converter, and potential solutions from a circuit design point of view. When I changed out the converter for one that was encased in metal, then grounded it, a great deal of the noise disappeared. When I further filtered both 12 and 5v sides with clamp-on ferrites and grounded the RPI case and the buck converter, the noise reached a "livable" point. I've ordered a few common mode filters from China to see how much more difference they make.
In interesting thought to implement a conventional regulator after the buck converter, although if the noise truly is common mode, I would think that it would still make it through.
I guess I should find a scope with a high enough frequency range to do some real scientific testing... then again, perhaps I should put down the soldering iron and go sailing!