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JohnSwenson

SMPS and grounding

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9 minutes ago, Cornan said:

The green/yellow cable is a ground wire ofcourse. It would be really dangerous without the IEC inlet grounded.

 

Yes but what is the ground used for on the PCB? If the chassi is isolated why would it be dangerous if there was no earth? 

 

I just want to know what they use the earth for if it is not connected to the chassi for safety reasons and if the chassi is not grounded it must be double isolated. I suppose the connect the filter capacitors to ground.

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Cornan   
12 minutes ago, octaviars said:

 

Yes but what is the ground used for on the PCB? If the chassi is isolated why would it be dangerous if there was no earth? 

 

I just want to know what they use the earth for if it is not connected to the chassi for safety reasons and if the chassi is not grounded it must be double isolated. I suppose the connect the filter capacitors to ground.

 

If you want to know more in details I suggest you ask the supplier for answers. They are usually quite quick to reply on Banggood.com.

The safety ground connection should be there for personal safety if something goes wrong.

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45 minutes ago, Cornan said:

The safety ground connection should be there for personal safety if something goes wrong.

 

Yes that is of course the main purpose but if the chassi is not connected to safety ground how will it protect anyone if something goes wrong inside. If the unit was double isolated it would not have any ground connection.

 

This got really of topic so I will leave it for now and check when my own Ghopert arrives. 

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sandyk   

Hi John

 The safety, and potential damage aspect of inexperienced members doing what you are suggesting worries me a little. (and may also contravene FCC requirements ?)

 Perhaps a compromise of something like a series 10 ohm .25W resistor at the equipment end of the added earth wire may be a good compromise ,and still be quite effective ? The series resistor could be inside a small length of heat shrink.

 

 Regards

Alex

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tims   

Appreciate it someone could explain what the effects these leakage currents have on different components and how they affect SQ. There's been a lot written about them recently but I'm still unclear about what they are and why we should minimiize them.

A link to another post explaining more would be fine.

 

Thanks.

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3 hours ago, mike eastman said:

John,  can you connect more than one of the adaptors to the same plug ? Any reason you couldn't eliminate the plug and connect the wire direct to ground wire in receptacle box?

Yes you could ground more than one SMPS from the same wire, just remember that the ground needs to come from the same circuit, preferably the same power strip/outlet box as the SMPS. So say you have two SMPS plugged into the same strip, then yes grounding them from the same wire is fine.

 

You COULD ground an SMPS from a wire connected to ta metal box IF that box is known to be grounded. I'm not going to be responsible for people taking outlet boxes apart to get to a ground wire.

 

John S.

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Em2016   
On 20/09/2017 at 12:27 PM, JohnSwenson said:

You may ask "how effective IS this?"

 

Here are some graphs, the first is the leakage current of an SMPS, the second is with this adapter plugged in:

 

Hi John, do these leakage current levels with this adapter method, come down to linear PSU leakage current levels?

 

Just speaking in terms of leakage current levels, not DC voltage noise/ripple of course.

 

 

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6 hours ago, JohnSwenson said:

I've been experimenting with some ways to make the SMPS a little easier or applicable to a broader range of equipment. First off is a way to use it with equipment that does not have a 5.5x2.1 barrel jack.

Ground_adapter_size.thumb.jpg.5e7c75d26eb2db90b687f7955902e2b2.jpg

 

I found another I had on hand, in this case the 7.5V Mean Well, this was exactly the voltage my switch took, IT plugs into the adapter, then a 5.5x2.1 to something else is used to plug into the device. In this case it was one of the adapters that came with the iPower. This works great. Using this technique I was able to ground the power to a bunch of different devices that had different plug sizes.

 

Both Amazon and Ebay have kits of these adapters available which include many different plug types.

 

Next up is an interesting kit from iFi called the Groundhog. It has a gounding system and several adapters to ground equipment in various ways. The one most appropriate is this:

Groundhog.thumb.jpg.47718bfe631b6bb4f9fa955284d1046c.jpg

 

This kit is unusual, it contains an IEC SOCKET, not a plug, you plug in a standard IEC power cord for your country. Most of you will already have several of these in your cable drawer. It doesn't matter what the country is, the IEC end is the same so they will plug right into the Groundhog. They call the adapter I show plugged in the "DC Spade", it is actually a little clip designed to clip onto the barrel of a 5.5 plug, thus grounding it. Clip it onto the barrel, then just plug it in.

 

This replaces the adapter shown in the first post with an off the shelf system you can buy, you don't have to build anything yourself. It is not dirt cheap, ($49), but for those that don't want to deal with building the adapter it is a nice alternative. It does exactly the same thing - it grounds the negative DC output of a power supply.

 

I hope this makes it a bit easier for people to try this approach.

 

John S.

 

Hi John,

 

Many thanks for for this simple DIY solution.

 

Would you consider this necessary with non-floating LPSUs like the HDPlex? I am powering my upstream switch, router, and modem with one of these, and wonder if I should be using these techniques to ground?

 

Also, would you get similar benefits by using a little IT like the B&K 1604A? Obviously this isn't the ultra low capacitance Topaz, but just wondering what your measurements show?

 

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mansr   
21 minutes ago, Ryelands said:

The 10/100 thing came from a passing remark in a post by John S a while back about Gigabit drivers being much more complex and busy, which makes sense.

The Ethernet drivers I've written or otherwise looked at work exactly the same regardless of the actual link speed. If you want to ensure the driver code is as simple as possible, you need to choose hardware accordingly. High-end server NICs (Intel, Broadcom) are the most complex, embedded controllers in SoCs the simplest. For use in a PC, I'd suggest finding an old PCI card such as a 3com 3c900 series. Those are simple and reliable. I think I still have a few in a box somewhere.

 

Of course, I don't believe any of this actually matters. I'm merely pointing out that forcing a lower link speed isn't going to do much at the software level, so if you think this is important, you're going about it the wrong way.

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rickca   
14 hours ago, JohnSwenson said:

it grounds the negative DC output of a power supply

OK here's a really stupid question.  Why don't they make SMPS with negative DC output grounded in the first place?

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Superdad   
39 minutes ago, rickca said:

OK here's a really stupid question.  Why don't they make SMPS with negative DC output grounded in the first place?

 

Yeah, I've been wondering that for weeks now since John starting playing with this during measurement sessions.  Probably has something to do with regulatory requirements.  A lot of the European regs are very strict with regards to what goes back into the mains--caring less about what comes out of the DC end.

I sent John a low-leakage "medical" Mean Well for testing a while ago.  It would be funny if the difference with that one was its grounding.  I'll ask him to check it.

 

Speaking of grounding--but not to be confused with this grounding of the output topic--I recently discovered (upon opening one) that although the Mean Well we offer for REGENs and LPS-1s has a 3-pin, IEC320-C14 socket, that ground pin is not connected to ANYTHING inside the SMPS!

(I still prefer to provide that style of unit--versus wall-wart or figure-8 C7 inlet--so that we don't have to stock and keep track of wall plugs/cables for all countries.  Everyone gets a 50cm USA cord that fits in the package and they can toss it or cut the end and put on a local plug--or whatever.)

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mansr   
19 minutes ago, Ryelands said:

I don't have the advantage of belief but I have experimented at length with LAN-related variables in an audio context. My only regret is that I didn't do it years ago.

 

I didn't advance an hypothesis as to why link speed might affect SQ nor am I clear what "the software level" is.

 

In light of John's passing remark, I did a five-minute trial, heard a worthwhile improvement and so continued to experiment at length. Mostly successfully.

A gigabit phy may well be less electrically noisy when operating at 100 Mbps. It is, after all, a much simpler system. By "software level" I meant OS drivers and other related software. I was under the impression you had hoped that the driver would put less load on the CPU and thus cause less noise if the link speed was reduced. Sorry if I misunderstood you.

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rickca   
44 minutes ago, Superdad said:

Yeah, I've been wondering that for weeks now since John starting playing with this during measurement sessions.  Probably has something to do with regulatory requirements.

So to use John's grounding technique, does this mean we now need two outlets for each SMPS (unless grounding multiple SMPS from the same wire)?  I'm impossibly dense about electrical things.

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Ryelands   
44 minutes ago, mansr said:

Sorry if I misunderstood you.

No problem but thanks anyway. As I quoted John from memory, I may not have got his point quite right. My point OTOH is that he's to blame for all this.

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