ground my laptop

[paulhm81]

Hi everyone
let me tell you my problem maybe you can advise me.

I connected a gtx 960 to my laptop using an egpu adapter that has a mini pci express cable that I connected to the laptop by removing the wifi card. It is powered by a pc atx psu and connected to a monitor. At the office it works very nice with very few problems but I brought the contraption at home so I can ocasionally play a game. The problem is that it keeps giving me an error that the gpu stopped responding and it recovered but it drops out of the game. I'm pretty sure it's a grounding issue because it mostly happens when the fridge starts or when the cfl's are lit in the kitchen. The only ground connection is with this mini pci express cable and I think it's not enough. The only difference between home an work is the monitor. At work I use a dvi connector but at home I have an older monitor that only has a vga and I use a dvi to vga adapter. I'm thinking of stripping a usb cable and using only the exterior of the plug but I'm unsure where to connect this - ground or minus on the psu? Do you have any advise? Thank you!


This youtube video shows a setup like mine so you cand have an idea only mine is using an external monitor:

[Ian.M]

Insufficient information.
Does the laptop PSU have a ground?
If it has a detachable mains lead with three pins at the connector, it almost certainly does. If it only has a two pin connector, it doesn't.

Is the GPU + EGPU adapter in a grounded metal case?  If not, you mayneed to build one, with metal mesh sides for ventilation.  As the purpose of the case is screening, it should be closely fitted to the GPU's bracket plate, and all case joints should be bare metal to bare metal, with either a copper braid gasket or overlapped with conductive adhesive copper tape, for good continuity.

Are your mains outlets grounded?

Are you using a filtered extension strip to power the laptop, PSU and monitor so they share a common ground?

Have you as far as possible routed the mains leads closely bundled together to minimise the loop area?

If you do have to attach a ground to the laptop, its best to use the binding screw post on a legacy port if it has any, and to use as short as possible wide tinned copper braid ground strap, terminated with a crimped fork lug attached by a screw to the binding post.  USB shells are less likely to offer a reliable ground connection.  Adding an extra ground connection without resolving the screening and EMI pickup issues may even make the problem worse by introducing a ground loop.

[SL4P]

On a laptop PSU, there is very little chance of the AC ground being connected r relevant to the DC 0V/ground inside the laptop.

My first shot would be as suggested above - to ensure decent grounded shielding of the GPU and connections.

After that tread carefully, and measure/confirm 'what is grounded to what' before tying them together.

[paulhm81]

Thanks for the reply

My laptop psu does have a ground but my understanding is that the grounding is only for the adapter, not for the laptop - correct me if i'm wrong. You just gave me an idea about another difference between office and home. At the office I have a universal supply for the laptop that doesn't have ground and at home I have the original psu that has one.
My mains are grounded and all psu's are powered from the same plain extention cord that is also grounded. I don't have a metal case for the egpu, it sits on the table as is.
I kind of understand the metal case idea but I'm wondering why it works at the office and not at home. I will bring the laptop psu that I have at the office and try it at home, maybe that's the problem.
Another thing - when the fridge starts or the cfl's at home I always hear some pops in the earphones. It's always done that.

[SL4P]

:::My laptop psu does have a ground but my understanding is that the grounding is only for the adapter, not for the laptop - correct me if i'm wrong.:::

No, I think you're on the money.
Grounding / shielding is easy to understand - hard to get right!

[Ian.M]

Laptop PSUs with two wire mains leads cannot have a grounded output.
However those with three wire leads can, and some certainly do.
e.g. I've just grabbed a Dell AA20031 PSU off the shelf and it has continuity from the AC in ground pin to the 0V pin at the DC plug. 

If you need to know if a laptop is grounded, the ONLY way to tell for certain is by checking continuity from the mains plug ground pin to the 0V on the DC connector.

CRT monitors are almost invariably grounded and the VGA cable shield and connector shell will be grounded.  Whether or not flat panel monitors are grounded depends on their PSU.  If its internal, with a three pin connector, its amost certain to be.  If its external, the situation is comparable to the laptop PSU.

[tggzzz]

On a laptop PSU, there is very little chance of the AC ground being connected r relevant to the DC 0V/ground inside the laptop.

I've seen direct connections between the mains earth and the adaptor's output. I've also seen them referred to as "IT PSUs", but I doubt that is a reliable designation.

If there is no direct connection, consider what will happen if the laptop is resting on someone's lap when a fault develops inside the PSU and HT reaches the output.

[tautech]

Graphics card monitor driver/s.
You say the monitors are different and no doubt the correct drivers for each will be too.
Get the latest from the monitor manufacturers (not from MS Windows or whatever OS you use).

[Monkeh]

Graphics card monitor driver/s.
You say the monitors are different and no doubt the correct drivers for each will be too.
Get the latest from the monitor manufacturers (not from MS Windows or whatever OS you use).

Monitors don't have drivers. Anything passed off as such is usually a colour profile (which is usually incorrect).

[paulhm81]

I just checked the original laptop psu and there is 1K between mains ground and the negative laptop end.
The issue is not with the monitor, it's with the external gpu. I only mentioned the monitor because at the office it's all good. I only had problems at the office while connecting something in the usb ports and not always. At home it's much more sensible and I don't know why. Today I will take my ungrounded laptop psu home and see if there is a difference. I will also try to ground my laptop from a usb port or something to the atx psu case and see if it helps. Unfortunately I don't have screws on any port on my laptop. Even the vga is just the port without the screws. I'm thinking of a usb port case without the power and data pins , soldered to a thick wire and connected to a screw on the atx psu.

[Ian.M]

The reason why I mentioned the monitor is because that usually introduces another ground path.

Wide copper braid is much more effective than wire of the same CSA for grounding high frequency signals.  You should run the shortest possible grounding strap from the GPU card bracket to the PSU case.

[paulhm81]

Thank you all for your answers!
I got it sorted out. I connected a cable from the usb to the metal case of the egpu power supply and it's ok. If I remove the cable and play with a air heater turning it on and off, the egpu gives me the error and if I connect the cable it's all good!
I found out that at the office the printer connected through a usb hub is grounding my laptop and that's probably why it didn't give me as much trouble!
Thank you again!