Blown up two laptops

[Lol999]

Okay, so I'm working on a cnc control board project with the Espduino 32 bit board and a cnc shield.
Everything is okay, I have stepper motors running as they should and all is gravy.

Then, working away I notice the psu for the cnc shield has the power led flashing, my laptop screen blurs and it's dead. Nothing. nada.
Tried a different psu and it's still doa and have to shell out £500 for a new laptop.

I assumed it was a faulty extension I had plugged both the shield psu and the laptop into so promptly binned it.

Just in case I use an old Dell for my next experiment, same set up.
I connect the Espduino via usb and flash it, no problems. I come back to the project and couple up the cnc shield to the Espduino, plug the power into it (12v 5a supply) and all is good, I then plug the usb into my laptop and another laptop bites the dust.

the psu is okay, it lights up until I plug it into the laptop and then it just switches itself off, no power, no nothing.

Firstly what can have happened, and secondly are the laptops likely beyond repair?

many thanks.

 

[crutschow]

Not sure what is happening, but it sounds like there is some sort of voltage/ground problem when the USB is connected.
So I suggest you look for an isolated USB connection (something like this), which should prevent any problem from that (or at least if it fails, it's a lot cheaper than replacing a laptop).

As far as repairing your laptops, I'm not optimistic.

 

[Harald Kapp]

Isolating the USB connection is a good idea to remedy at least the symptoms. It will not resolve the underlying cause. It sounds like there is a kind of fault current flowing between PSU and laptop. Although you say "the psu is o.k.", I'd suspect the isolation system of the psu being at fault. Check the isolation between the PS's output and the input terminals.

 

[Lol999]

thanks for the advice folks, much appreciated.
I live in the UK so would one of these offer sufficient protection against future problems?
https://www.ebay.co.uk/itm/184440645025?hash=item2af184e5a1:g:ge0AAOSwm9xfWSPk

 

[Harald Kapp]

Sounds reasonable. Have you read this caveat?

This product supports full speed devices, but does not support pure high speed devices (USB2.0).

 

[Lol999]

Sounds reasonable. Have you read this caveat?

yeah, my understanding is it runs at 12Mbps?
I would only be using it as an interface between my laptop and a cnc laser machine, biggest file I have is 2MB so I'm guessing it won't be a bottle neck?

 

[Harald Kapp]

it runs at 12Mbps?

yes.

I'm guessing it won't be a bottle neck?

Probably not, but I'm not qualified to answer this in a qualified manner.