[GreenKeys] Problem with Current Loop to RS-232 Converter on ASR33

[Clay Archer]

It sounds like the current loop side is going into "open loop".   Does your
RS232 converter have a model number or any identifiable markings, or is it a
"home brew" box?   If you could open it up and post a photo that would be
helpful.  I would expect to see some opto-isolators and an RS232 driver
chip.

 

Most RS232 to current loop converters require an external power supply to
provide the loop current, and sometimes to power the RS232 side.   Sometimes
there is an extra connector on the "box", or it may expect the extra
voltages through the DB connector.

 

Clay

 

 

  _____  

From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Rob Jarratt
Sent: Saturday, January 19, 2013 11:31 AM
To: greenkeys at mailman.qth.net
Subject: [GreenKeys] Problem with Current Loop to RS-232 Converter on ASR33

 

The ASR33 I got came with a little box that I assume to be a Current Loop to
RS232 converter.

The ASR33 behaves rather oddly when I plug the RS232 connector into
anything. When the connector is not plugged into anything the ASR33 ticks
over as I believe it should. However when I plug the connector into a
socket, even if the socket is not connected to anything else, the ASR33
starts acting a little as if it receiving characters, the cylinder with the
characters embossed on it "vibrates" but does not print anything. If I plug
it into my breakout box, with the other end not connected to anything, it
acts in this way and I notice the Rx light come on, which of course it
shouldn't as nothing is being sent to it. It is almost as if there is a
short to the Rx line. I have checked the connector for shorts but there
don't seem to be any.

Has anyone ever come across behaviour like this?

Regards

Rob

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