Using RS485 converter like BLACKBOX IC624A-F

Recently I upgraded my Laptop and found that I do not have a comm port (rs232) anymore.

I ended up buying a PCMCIA RS232 adapter which works fine for most PLC applications. I use it successfully with GE-FANUC CIMPLICTY ME, and also A-B RSLOGIX 500.

The problem I am facing is that it works fine with the RS232 port on the PLC, but when I try to connect my RS485 connector to connect to the DH485 RJ45 port I get a communuciation error.

Has anybody out there used a RS 485 connector successfully with a PCMCIA RS232 adaptor? Any ideas?

Thank you in advance.
Venky

The IC624A-F has an RJ-45 on the 485 side. Are you sure it's wired right?

Black Box's generic "Async RS-232 Interface Converters" blurb claims that their converters don't need power, but I've run into numerous occasions (6 off the top of my head) where port powered converters did not work, but as soon as a powered 232-485 converter was used, communications was established. If you have an alternative powered converter, you might try that one. I suspect that this is more due to the PC's inability to source enough power, but the failure of port powered converters is not unusual by any means.

Some manufacturers switch nomenclature of the A and B lines. It pays to swap the A and B lines at one end to see if that's the problem. It can't hurt, because 485 is a diffential mode sense and it's not like grounding out a powered line.

Termination of RS-485 line becomes critical at higher data rates and longer line distances, but it sounds like you're trying 485 locally - with short cables, where termination isn't a big deal, especially if you're working at 19.2K baud or less.

opinion mode: I have tossed 2 or 3 Black Box 232-485 converters in the trash over the years, after not being able to get them to work, even when substituting each in a known good working circuit. I think Black Box is great for other stuff, but I am not enamoured of their converters. I prefer B&B Electronics, which I've used with greater success.

Dan