TS Adapter short circuit

[drozdu 0]

Hello, Yesterday I was working with Siemens TS Adapter V5.2 for direct connection PC <-> PLC. I don't have a COM port in my laptop, therefore I was using PCMCIA to RS232 adapter. The TS adapter was connected to PLC (ES200S / IM151-7 CPU - there was profibus cable going from PLC to touch panel, so adapter was actually connected to profibus plug). When I was trying to connect the RS232 cable to COM port on my PCMCIA card I touched (by accident) pin no 5 with plug housing (cable was shielded). There was a short circuit with flash, smoke and so on. TS adapter was seriously damaged, the inner side of adapter was burned in places where it was touching MPI and COM cable shield, some parts on PCB were burned too. Does anyone have idea why the short circuit current was so large? (Just don't tell me: Because resistance was low ;) ) I enclose the circuit diagram of TS adapter, which I have found in siemens manuals. Best regards, Bartek

[JesperMP 2]

I am guessing that there were a big potential difference between the ground of your PC and the ground of the PLC. When programming, if it is possible I use a 230V power outlet in the panel rather than from another source.

[drozdu 0]

That's how I connected it, so there shouldn't be potential difference :/ Besides - does laptop computers have any grounding? I mean, the AC adapter is grounded, but laptop itself is isolated from AC power line (there is only DC line going from AC adapter to laptop - correct me if I am wrong). Edited 25 Nov 2009 by drozdu