[geeks] RS232 / RS485 opto-isolated converter

[Joshua Boyd]

On Wed, Dec 21, 2011 at 04:15:47PM -0500, Patrick Giagnocavo wrote:
> I have a number of Carel brand, RS232-RS485 opto-isolated converters,
> cheap!  No power supplies, but they take 12V with what looks like a
> typical plug.
> 
> RS232 is DB25 female connector, RS485 side is both 3-wire and what looks
> like an RJ45 style jack connector.
> 
> What exactly would they be used for?  I have no idea what you do with an
> RS485 "network" ...

RS484 is serial, but usually for numerous machines sharing the same line
in a master slave relationship.  For instance, I've seen it used for
control panels, where the device to be controlled sends poll messages to
each panel in turn, waits a set time for a reply, then sends to the next
panel.  A panel saves any commands it has until it is polled, then
replies.  Often it is half duplex and moderately frequently I see it
over coax even though the spec calls for differential.

This is commonly used for industrial control, lighting control, and
other sorts of low speed control.

If you don't already have 485 stuff that you want to talk to, there
probably isn't much point in trying to put the adapters to use.

BTW, see http://en.wikipedia.org/wiki/RS-485