[time-nuts] Warning about "slef-powered" RS-422 to RS-232 converers

Bob kb8tq kb8tq at n1k.org
Wed May 31 06:40:04 EDT 2017


Some of them need a pair of control lines driven in opposite states to work well. Others need the control lines 
driven to a + voltage. Most are unhappy with < 5V signaling. Without a hammer and a microscope it’s generally 
a bit tough to figure out what the constraints are :)


> On May 30, 2017, at 1:20 PM, Mark Sims <holrum at hotmail.com> wrote:
> While playing with the RFTG-m GPSO I tried using a couple of RS-422 to RS-232 converters.  These converters can be externally powered or "self-powered" by the RS-232 signals.
> Both units worked fine as long as the RFTG was only sending the 22 character ASCII time code message once per second.  But when the RFTG was sending binary data along with the time code message they flaked out.  Apparently the converters power generator can't generate enough power when they are handling a lot of data.
> One of the converters I tried was made by Hexin.  The other was a no-name Chinese mystery unit.  Also some USB serial port dongles can't properly power the converters no matter what data they are processing.
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