Grounding metal keyboard cases

[glibber]

Hi all,

I've dug up a few old threads about ESD and grounding cases, but I'm not really an expert with electronics and want to make sure I'm going right about grounding a metal case. From what I understand, the most important risk here is ESD that you introduce by touching the case finding a way to ground through other components, potentially damaging them. The way to circumvent that should be connecting the case to ground directly.

So here come some things I'm unsure with:
1. The plating on a PCB's mounting holes should be ground, right? So with a tray mount the case should be grounded via the standoffs.
2. I also often see dampening mods with rubber O-rings for tray mounts, basically sandwiching the PCB between two of those o-rings. Doesn't this include the risk of the case not being grounded (if the screws don't happen to touch the plating inside the holes)? Should you create an additional connection from ground to the case?
3. Do top/bottom/sandwich mounts make additional grounding necessary, e.g. by connecting the plate (if it's metal) to ground on the PCB?
4. Is it a good idea to ground a (metal) plate like that in general?

What do you think about these, are they right/wrong/utter nonsense?

[yui]

really the likelihood of you killing the thing from static on the case is rather low, you would need a component right against the case.
and really you can't quite ground an anodized case, the aluminum oxide is a rather good insulator, and the case will often absorb the energy too, a large mass has some capacitance to air and ground.
TL;DR do not worry about it too much, as long as you do not have wireless inside grounding will not hurt anything, and lack thereof is also very unlikely to hurt anything

[tp4tissue]

Well first check if you have a working earth ground. some old houses don't have it, and many countries don't have it. Even though they may have a 3prong socket

Now, move your finger lightly across the top of the metal casing on your pc, exposed metal,  if you feel a fuzzy, lightly prickly feeling (distinct from your chair or table),  then that means it's not properly earth grounded,  if that's the case, nothing you can do to the keyboard would ground it.

If you feel your metal keyboard, and there's no prickly feeling, well then either it's not connected to the electric ground at all, or it is properly grounded.

[yui]

Well first check if you have a working earth ground. some old houses don't have it, and many countries don't have it. Even though they may have a 3prong socket

Now, move your finger lightly across the top of the metal casing on your pc, exposed metal,  if you feel a fuzzy, lightly prickly feeling (distinct from your chair or table),  then that means it's not properly earth grounded,  if that's the case, nothing you can do to the keyboard would ground it.

If you feel your metal keyboard, and there's no prickly feeling, well then either it's not connected to the electric ground at all, or it is properly grounded.

computer power supplies have a galvanic insulation, even if they are not grounded at all you should not feel anything at all on exposed metal, if you do it means that the insulation is starting to fail and you really either fix it or throw it away before it get much worse, and also that you have no ground to that plug but either way leaky supply = bad, could kill you, or worse, kill your pc

[glibber]

I might be a bit too anxious about this, I just saw some people saying they had their keyboard damaged, so I wanted to be safe about it.

Well first check if you have a working earth ground. some old houses don't have it, and many countries don't have it. Even though they may have a 3prong socket

I know for sure that we have a ground connection here in the house.

Now, move your finger lightly across the top of the metal casing on your pc, exposed metal,  if you feel a fuzzy, lightly prickly feeling (distinct from your chair or table),  then that means it's not properly earth grounded,  if that's the case, nothing you can do to the keyboard would ground it.

Not sure if I quite get that - couldn't I ground the case by connecting it to ground (and making sure it's isolated from other voltage levels in the PCB)?

If you feel your metal keyboard, and there's no prickly feeling, well then either it's not connected to the electric ground at all, or it is properly grounded.

Well that's not very fool proof 

These were more theoretical thoughts though. I'm considering getting/making a non-anodized aluminum case, maybe sandblast or brush it, and just wondered if I have to consider that kind of stuff.

[Findecanor]

Well first check if you have a working earth ground. some old houses don't have it, and many countries don't have it. Even though they may have a 3prong socket

Now, move your finger lightly across the top of the metal casing on your pc, exposed metal,  if you feel a fuzzy, lightly prickly feeling (distinct from your chair or table),  then that means it's not properly earth grounded,  if that's the case, nothing you can do to the keyboard would ground it.

If you feel your metal keyboard, and there's no prickly feeling, well then either it's not connected to the electric ground at all, or it is properly grounded.

computer power supplies have a galvanic insulation, even if they are not grounded at all you should not feel anything at all on exposed metal, if you do it means that the insulation is starting to fail and you really either fix it or throw it away before it get much worse, and also that you have no ground to that plug but either way leaky supply = bad, could kill you, or worse, kill your pc

I don't believe that a prickly sensation when you've got a two-pronged wall socket is a reason to be alarmed.
I've got only a two-pronged socket in most of the rooms of my apartment, unfortunately, which is not an ideal situation. But there should be no imminent danger.

I have used two power supply units: one Delta and then a Seasonic: both considered top brands who make their own units, both bought new from reputable vendors. From day one with each, when brand new, I've got a tingling sensation when touching the anodised aluminium surface of my PC case. (Jonsbo U3)

[glibber]

I'm getting more and more confused with this now

Would my originally mentioned methods/ideas work to ground my case?

[tp4tissue]

Well first check if you have a working earth ground. some old houses don't have it, and many countries don't have it. Even though they may have a 3prong socket

Now, move your finger lightly across the top of the metal casing on your pc, exposed metal,  if you feel a fuzzy, lightly prickly feeling (distinct from your chair or table),  then that means it's not properly earth grounded,  if that's the case, nothing you can do to the keyboard would ground it.

If you feel your metal keyboard, and there's no prickly feeling, well then either it's not connected to the electric ground at all, or it is properly grounded.

computer power supplies have a galvanic insulation, even if they are not grounded at all you should not feel anything at all on exposed metal, if you do it means that the insulation is starting to fail and you really either fix it or throw it away before it get much worse, and also that you have no ground to that plug but either way leaky supply = bad, could kill you, or worse, kill your pc

YUI, seriously what is going on with you lately, 

PSUs CAN NOT be galvanically isolated FROM the WALL, OR the computer,  that doesn't make any sense.

The PSU's groundpin is usually directly tied to the neutral pin, and all of that through the Casing and mobo ground plane.

That's the Only way it works, and ONLY way it has EVER Worked.

Every computer ever made, if it doesn't have a ground earth pin, (which is NOT galvanically isolated), it will have a fuzzy prickly feel on all surfaces, even through thin painted surfaces. 

[yui]

all pc power supplies i ever repaired or recycled had proper insulation, well if the transformers were not burnt that is,
1st stage filtering and "High" voltage DC, this one is relative to neutral
2nd stage high frequency switching and transformers, i so far never found auto transformers in any ATX supplies, so they provide insulation
3rd stage smoothing and in modern supplies 5V and 3.3V generation

that 2nd stage, often between the 2 radiators provide the insulation, and even on ungrounded plugs i never felt anything on the metal of the cases, unless it was one with a damaged transformer or transistor insulation pad.

[Leslieann]

You should not feel anything touching the case, you should not feel any power, that is the whole point to protect you from the electricity running through it. Try that standing barefoot in a puddle and it may not feel so tingly. If you feel anything it should be the static leaving you, not leaving it.

As for static ruining parts, do you think they make anti-static mats and wrist bands for show? If you do you might work at The Verge but the rest of the industry doesn't and for good reason, it kills parts. I've personally seen it destroy ram and it did a number on the programmable controller in my Filco, it still works but its glitchy.

How to protect it, it really doesn't matter how you do it but you want to connect the case to the ground pin or a grounded area on the PCB (as close to the USB cable as possible) or the usb port housing (this connects to the shielding). It doesn't need to be soldered or anything just be in contact. On the Filco I spliced into the internal dongle on one end and taped the other end to the case. On my Novelkeys I taped a small wire to the case and ran it through the cutout for the usb port, when assembled they are forced to contact each other. Neither is as good as a proper grounding strap, but still better than nothing.

[tp4tissue]

Alot of equipment is chained together, and they all get grounded even if some are 2 prong, for example, an HDMI cable connecting your tv to your pc, that TV is now grounded because it now has an earth ground which goes through the shielding of the HDMI cable through the pc gpu through the ground pin of the pc..

This is why some might think 2 pin = grounded, or that 2 pin doesn't affect grounding, it most certainly does.

It is always the case, if you take a macbook, aluminum body, and it's 2 pin only, there will be a fuzzy numb feel on the surface if you lightly run your fingers across it. This will be the behavior on any 2 pin electronics with exposed metal surfaces.

[glibber]

I really didn't want to start an argument here

I just want to know if my approach to grounding is correct, so I don't accidentally short anything...

[yui]

USB = current limited and short protected, unless using a mac, so even if you do short something, as long as you are not on a wireless board with li-ion batteries you really should not damage much of anything with a short (only talking about USB2 powered stuff).
and yeah TP4 and me can have heated debates on everything it seems