[sdiy] Quick Question about Grounding Power Supplies

[Shawn Rakestraw]

Thanks for the link Vlad and I appreciate your answer Richie. The case is
wood. I went ahead and connected the earth ground to the 0V of the
secondary. Should I try to connect a gnd wire to the aluminum rails? That's
the last question I have about this. I appreciate you all!

On Fri, Jul 3, 2020 at 5:06 PM Richie Burnett <rburnett at richieburnett.co.uk>
wrote:

> Yes, the mains protective earth should be connected to the 0v output on
> the low-voltage side for safety, (and the enclosure if it is metal!)
> Otherwise one of the following scenarios can result in dangerous mains
> voltages appearing at the low voltage output:
>
> 1. A high-voltage mains wire becomes disconnected and comes into contact
> with one of the low-voltage wires on the secondary side of the transformer.
> 2. The transformer's primary/secondary insulation fails and they windings
> come into contact.
> 3. There is a high-voltage transient (potentially 1kv+) on the mains
> supply that could arc over to the secondary side wiring if creapage and
> clearance distances are not sufficient.
>
> If the secondary side is earthed (grounded) any of these scenarios should
> result in either a blown mains fuse or a tripped circuit breaker. Either
> way the mains power is cut off due to the large fault current flowing to
> earth and nobody receives a nasty shock.
>
> Only exception is if the transformer is Class 2 (double insulated.) Many
> small wall wart power supplies are made this way. Often potted to ensure
> the high voltage and low voltage sides cannot come into contact, and
> prevent flashover etc.
>
> -Richie,
>
> Sent from my Xperia SP on O2
>
> ---- Shawn Rakestraw 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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