[sdiy] Quick Question about Grounding Power Supplies

Vladimir Pantelic vladoman at gmail.com
Fri Jul 3 22:47:37 CEST 2020

On 03.07.20 22:38, Shawn Rakestraw wrote:
> Thanks for the answers. Looks like I may have opened a sensitive topic.
> I guess with a 10 ohm resistor and cap it is pretty near the same as
> straight connected. What is the purpose of the resistor? Is it to act as
> a fuse in case of short?

I think the idea is to act as a high impedance in a 50Hz ground loop and
the cap is to let HF pass to GND unimpeded.

also of note:

> On Fri, Jul 3, 2020 at 3:53 PM Michael E Caloroso
> <mec.forumreader at gmail.com <mailto:mec.forumreader at gmail.com>> wrote:
>     Never connect earth to the CT of a transformer.
>     At least here in the US, earth of a three prong AC plug should be
>     connected to the metal chassis.  Local circuit ground should be
>     coupled to earth through a low resistance (IE 10ohm at least 1/2 watt)
>     with a cap in parallel.  That would be a better solution to reducing
>     noise.
>     MC
>     On 7/3/20, Shawn Rakestraw <shawnrakestraw at gmail.com
>     <mailto:shawnrakestraw at gmail.com>> wrote:
>     > Some of you may remember helping me learn how to design some PCBs
>     a few
>     > months back. I have been using one of my homemade eurorack cases for a
>     > while now. To refresh the idea, it is essentially an electronotes
>     design
>     > where a 24V center tapped transformer is regulated down to +12V
>     and -12V.
>     >
>     > My question is this - Should the ground pin of the power cord be
>     connected
>     > to the center tap of the transformer? Currently, I have it
>     connected to the
>     > "Earth" terminal of the power switch and it is also connected to
>     the "Body"
>     > of the transformer, but I have left the center tap "Floating".
>     >
>     > After putting a Make Noise Pressure Points module into the case and
>     > noticing what looks like a lot of noise on the signal, I think
>     that maybe
>     > the earth ground should connect to the center tap and floating ground.
>     >
>     > Thanks for your advice.
>     >
>     > - Shawn
>     >
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