[GreenKeys] RS232 to current loop dongle

[Ed Sharpe Archivist for SMECC via GreenKeys]

Yes, but will it  handle   60 ma, hi voltage and the kick  back  from the 
coil?
Inquiring minds want to know....
 
 
In a message dated 12/8/2014 10:21:13 P.M. US Mountain Standard Time,  
jdangus at att.net writes:

On 12/8/2014 10:48 PM, drlegendre .  wrote:


I don't see any reason this shouldn't work, but  there's something that
might need to be pointed out.. take a look at this  line from the specs: 


"Power: Interface powered or  external 9V DC/300mA power
acceptable"


To me, this means that it's a  passive interface, and cannot supply
the loop current for the CL side.  So, unless your CL equipment
has active (powered) interfaces, you're  going to have to use some
kind of external power supply. Otherwise, it's  the correct device for
the job. 

It is a  passive interface by itself. The suggested source for the external 
loop
is  a 9 volt DC source.

If I remember correctly, a Model 15 selector magnet  is around 60 ohms, 
but it's also a fairly large inductance. Which is also  WHY they use a 120
volt supply. So as to act as a current source with high  compliance to
overcome the inductance and get the waveform to better  approximate a
square wave with minimum distortion.

The only  "correct" application for this converter is talking to a matching
converter  at the other end and at a distance of under 3200 ft.

If you're looking  for a method of safely dealing with vintage Teletype 
gear,
this _<http://www.aetherltd.com/connecting.html>_ 
(http://www.aetherltd.com/connecting.html)   is a "know to be good"
implementation.


-- 

Jeff-1.0

wa6fwi

_http://www.foxsmercantile.com_ (http://www.foxsmercantile.com/) 


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