SMPS and grounding

[Speedskater]

No, connecting a metal chassis (case) to a Safety Ground/Protective Earth is NOT always a MUST, if:

a] if it's a double-insulated case (square with-in a square safety symbol). You must not add a SG/PE wire to it's internal chasses.

b] the unit is battery powered. But it may have continuity to the SG/PE thru cable shields.

[Speedskater]

On attaching Safety Grounds, commons and shields

Neil Muncy(RIP) wrote his AES paper on these almost 25 years ago, but there is still much confusion.

 

a] Safety Ground: is attached to the chassis near where the AC cord enters the chassis.

b] audio circuit common: is attached to the chassis at a single point near the input connectors.

c] DC supply common: is attached to the chassis at the same single point as the audio circuit common.

d] cable shield: is attached to the chassis at it's chassis connector. Experts have different view-points has to whether both ends or one end of the shield should be attached.

[JanRSmit]

18 hours ago, Speedskater said:

On attaching Safety Grounds, commons and shields

Neil Muncy(RIP) wrote his AES paper on these almost 25 years ago, but there is still much confusion.

 

a] Safety Ground: is attached to the chassis near where the AC cord enters the chassis.

b] audio circuit common: is attached to the chassis at a single point near the input connectors.

c] DC supply common: is attached to the chassis at the same single point as the audio circuit common.

d] cable shield: is attached to the chassis at it's chassis connector. Experts have different view-points has to whether both ends or one end of the shield should be attached.

Indeed, correct. Especially forclow freq noise,

[Speedskater]

5 hours ago, JanRSmit said:

Indeed, correct. Especially forclow freq noise,

Not just at low frequencies, at all frequencies.

Jim Brown, EMI/RFI guru writes:

Antenna Action The most fundamental cause of interference to other systems is the fact that the wiring for those systems, both inside and outside the box, are antennas. We may call them "audio cables" or "speaker cables" or "DC supply cables" or "AC cords" or printed circuit traces,but Mother Nature knows that they are antennas! And Mother Nature always wins the argument.

[JanRSmit]

3 hours ago, Speedskater said:

Not just at low frequencies, at all frequencies.

Jim Brown, EMI/RFI guru writes:

Antenna Action The most fundamental cause of interference to other systems is the fact that the wiring for those systems, both inside and outside the box, are antennas. We may call them "audio cables" or "speaker cables" or "DC supply cables" or "AC cords" or printed circuit traces,but Mother Nature knows that they are antennas! And Mother Nature always wins the argument.

In a paper from Bill Whitlock on grounding of 2012, and another paper i have not yet found back, a clear distinction is made between low and high frequency behaviour. 

Bill does pay a tribune to Neil Muncy. https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

 

[Speedskater]

Mr. Brown is in this case writing about shielding and interference antennas.

* * * * * * *

That Bill Whitlock seminar paper (it's more like a Power Point with notes) is excellent.

[marce]

On 8/17/2019 at 1:16 PM, JanRSmit said:

I understandy youruse of common.

Whether the chassis is connected to safety ground is a dangerous assumption.

With electronics with a 2-prong mains plug it is not.

Whether it is connected to the common as you defined it and if so how is another thing you should not assume.

 

Connecting the chassis (case) if it is metal to safety ground (the thirth prong on the mains plug) is a must. This also implies the requirement that the safety ground on the outlet is proper functioning.

In case of a Netgear switch i have it is not. (2 prong plug) Thus i need to create a connection to safety ground.

In other words you have to check.

 

 

 

Double insulated don't connect to PE.

[JanRSmit]

3 hours ago, marce said:

Double insulated don't connect to PE.

Double insulated with a metal case? Please explain hoe.

[octaviars]

6 minutes ago, JanRSmit said:

Double insulated with a metal case? Please explain hoe.

 

Class II equipment has reinforced or double insulation. As well as the basic insulation for live parts, there is a second layer of insulation, either to prevent contact with exposed conductive parts or to make sure that there can never be any contact between such parts and live parts. The outer case of the equipment need not be made of insulating material; if protected by double insulation, a metal case will not present any danger. It must never be connected with earth, so connecting leads are two-core, having no protective conductor.

The part "it must never be connected with earth" often fails in a normal hifi system. For example if you connect a double insulated component with a RCA connection to a component with protectiv earth the case of the double isolated component will seek earth through the sheild of the RCA cable.

[Speedskater]

40 minutes ago, octaviars said:

The part "it must never be connected with earth" often fails in a normal hifi system. For example if you connect a double insulated component with a RCA connection to a component with protectiv earth the case of the double isolated component will seek earth through the sheild of the RCA cable.

No, that probability is taken into account when then unit is safety tested.

The 'never' part is about modifying the unit by adding a ground wire.

[marce]

PE protective earth and return current paths are different. Protective Earth (ground as it is often called) is for protection only.

[octaviars]

10 hours ago, Speedskater said:

No, that probability is taken into account when then unit is safety tested.

 

Well of course it is.

 

10 hours ago, Speedskater said:

The 'never' part is about modifying the unit by adding a ground wire.

 

Perhaps I should have written it different and as you write it involves any type of modifying a class 2 unit with a PE.

 

1 hour ago, marce said:

PE protective earth and return current paths are different. Protective Earth (ground as it is often called) is for protection only.

 

Yes of course but the idea of class 2 products and metalcases was good until they started using SMPS.

[Steffenegede]

Hi, I've bought a linear psu from China. The protective earth is not connected but I guess drilling a hole and attaching a cord is ok? Maybe I haven't been paying attention but would adding a john swensson ground shunt, to the router I'll be powering,  help anything with a linear psu or is it only smps's that'll benefit from it?

[Speedskater]

23 minutes ago, Steffenegede said:

Hi, I've bought a linear psu from China. The protective earth is not connected but I guess drilling a hole and attaching a cord is ok?

Does it use a two conductor power cord?

Does it have a Double Insulated enclosure (Square within a Square safety symbol) ?

[Steffenegede]

24 minutes ago, Speedskater said:

Does it use a two conductor power cord?

Does it have a Double Insulated enclosure (Square within a Square safety symbol) ?

This is the exact model: https://www.ebay.co.uk/itm/50VA-HIFI-Ultra-low-Noise-Linear-Power-Supply-DC5V-9V-12V-15V-18V-24V-LPS-PSU-/273372400529 

[dongi]

I bought wrong DC connectors so I put two nails (I also matched its color to the one here, lol) and plug them together.

+ to +, - to -

 

One end of the wire goes to the ground only (no N & L) and the other end of the wire goes to the negative (-) of the DC adapter.

 

I measured and with everything plugged in, the voltage shows what is supposed to , 12.15V (it is a 12V adapter). 

 

So, did I do it correctly? I mean it works but I am not sure if the nails or my connections are correct. I am not the best when it comes to these things, hence the question

 

[Superdad]

7 minutes ago, dongi said:

I bought wrong DC connectors so I put two nails (I also matched its color to the one here, lol) and plug them together.

+ to +, - to -

 

One end of the wire goes to the ground only (no N & L) and the other end of the wire goes to the negative (-) of the DC adapter.

 

I measured and with everything plugged in, the voltage shows what is supposed to , 12.15V (it is a 12V adapter). 

 

So, did I do it correctly? I mean it works but I am not sure if the nails or my connections are correct. I am not the best when it comes to these things, hence the question

 

 

Maybe post a picture. Doing things with nails and electricity makes me very nervous. Not going to condone any dangerous contraptions! 

[dongi]

4 minutes ago, Superdad said:

 

Maybe post a picture. Doing things with nails and electricity makes me very nervous. Not going to condone any dangerous contraptions! 

Oyyy so difficult to take a photo  It is hooked up and it is dark in the back of the system. However, there is nothing to see really. You know at the very first page of this thread, there is a photo. It looks almost exactly like that (I say almost because I cut the nails short so the DC adapters/connectors go into each other all the way and you cannot even see the nails. They are both flushed to each other. I don't know, isn't the nail a conductor too?  Hahaha

[dongi]

OK, I took a photo of the cut pieces to show you how and what I connected them with.

 

They go into each other all way in. Imagine they are flushed. The wire I forgot to demonstrate for you  but the wire goes to the negative (-) part of the one on the right (male) in the picture.

 

[Superdad]

2 minutes ago, dongi said:

OK, I took a photo of the cut pieces to show you how and what I connected them with.

They go into each other all way in. Imagine they are flushed.

 

Oh, now I see. That's fine.

[dongi]

Yeah, it was stupid my mistake when I ordered it. This was a solution I thought it might have worked.And I guess it did work  Thanks Superdad!

[APPROXIMATE]

!st attempt worked GREAT !

[sandston]

I wanted to share a solution I just came up with for implementing the DC shunt cable into ones system. I've introduced the shunt onto some of my power supplies and feel like there is a noticeable decrease of hash in the high frequencies. However having several nice DC cables from Ghent I didnt want to permanently introduce these low end DC connectors that have been suggested permanently into my system. I ordered some Copper Retaining Rings from McMaster Carr linked here. 

 

https://www.mcmaster.com/98410A605/

 

These rings snugly fit on the outside of the DC 5.5mm DC barrel. No need to worry about the inetrnal 2.1 or 2.5mm barrel anymore. I soldered a wire onto one side of the retaining ring and slid them over the outside of the barrel. These guys are quite small and the soldering is fussy but I managed 3 in about 20 min. I used 24 guage wire and even with this light guage I had to trim a couple strands to get the wire to sit in the little notch. One trick was to twist the ring a bit so the ends are not touching. This helps to keep from soldering the ends together. Be careful not to get solder on the inside of the ring so you get good contact with the full circumference of the barrel to the ring. Once your done soldering trim the extra wire and just twist the ends of the ring back together. Its a tight fit but easy enough to get them on without tools as the wire helps to spread the clip open. If your solder joint is cold you will know right away when you tug on the wire. I hope some of the members like my solution as it will feel nice to give back to the AS community which I have gotten so much out of.

[sot13]

Just bumped on this thread and I was interested in trying the trick. The issue was that I did not have the tools at hand, apart from some wire and a plug. So I thought of this simple solution. I wrapped tightly the wire with the help of pliers and the other end went to the plug! Its cheaper and fast! (admittedly not as elegant)! 

[sot13]

@JohnSwenson please help me out here: I am going to implement the DC shunt cable in the following setup

The question is the following: would this setup, "destroy" the isolation (galvanic?) offered by the Fiber optic cable? Would it be preferable to use the DC shunt cable ONLY on the opticalModule's power supply? Thank you in advance!