Serial Port Protection

Hi all

I have just managed to blow up my laptop while programming a Modicon Momentum. A wrong connection and me not checking the wiring first, caused a surge through the serial port and has blown the motherboard.
What I want to know is, does anyone know of a device (Such as a surge arrestor or an isolator) that I can plug between my laptop and the programming port that can protect my laptop? It must be universal because I program several different kinds of PLC.

Thanks in advance
Dave

Went through something similar a while back. Here is where poeple helped me out.

Steve

Thanks Steve. Thats just what I was looking for.
Glad to know that I'm not the only one who *&*$%$£ up.

Dave

Ahhhhh....Never forget the old saying:

"The more you *&*$%$£ up, the faster you get promoted".

Steve

Some time ago i had a similar problem. The PLC power supply ground was floating (as the 220/24V transformer hasn't ground connector) and the PC was referenced to ground.
Then it generated a differential tension between the PLC and the PC port ground.
The easiest solution was take off the ground from the PC and screen PC (because it is wired to the PC). Another solution would be to buy another power supply for the PLC with a good ground.
By the way exists a overvoltage protection by Weidmuller for serial port, that could avoid damage your PC serial port.
Sorry for my english.

WEll, com port isolation is great but what about the
laptops power supply? If you can get the line voltage
to the exposed metal parts of your computer
that computer should be fried...
(or maybe you like your laptop more than yourself )

See post on "grounding 24 VDC from okie bob, ME)

PLC at one L2 and the "convienence outlet" at another. What is the magnitude of the potintial from one outlet to the other.

Well, original post was by Dave Steer who seam to live in
Britain. Line voltage over there is 240VAC if I'm not mistaken
and in three phase system voltage between phases should be
some 400V (or ca 415V according to my calculator).

Even if the phases were offset by 180 instead of 120degrees,
that would still make only 480V.
I don't know what is the requirement by national standard in
Britain but typical power supply isolation should be 1000V
or more.

If the potential difference between "convenience outlet"
and equipment you were working on is more than that,
kindly ask the customer to buy you a nice new laptop
or get a lawyer. Let him call your customer and offer
a choice of paying for your precious laptop or call
your local ESA inspector (electrical safety authority)
to shut their plant down.

If this is not the case and you suspect laptop problem
call ESA inspector and arange for high-pot test.
If the device doesn't pass, return product for refund and
submit the ESA receipt (or get a lawyer ).

If this isolator can delay the communication? I use portable PC connect to siemens S5, if the isolator may bring on a 'Time-out between data'?

If you are thinking about delay of RS232 optoisolation, don't worry.
Signal is transferred in real time. You can think of it as
if it was cable. Check out www.rs485.com for lots of info including
schematics...

panic mode