[time-nuts] RS 232
Tim Shoppa
tshoppa at gmail.com
Thu Jul 25 15:58:31 UTC 2013
A lot of these questions can be side-stepped today because few to no modern
PC's have built in RS-232 serial ports.
And if you are going to add a serial port you can just put in a RS-422 PCI
card or RS-422 to USB interface instead. A big win, and it makes much more
sense to leach +5V off of USB than it does to leach power off RS-232
control lines.
Many time-nut devices are already RS-422 (e.g. Z3801A) serial and
differential for PPS, and it makes little sense today to backhaul to RS-232
when a new PC won't have native RS-232 support anyway.
Tim N3QE
On Thu, Jul 25, 2013 at 9:39 AM, <EWKehren at aol.com> wrote:
> Since joining time nuts over four years ago I have not used a single MAX
> 232 chip. Two reasons MAX do not give me isolation and do generate noise
> in
> critical applications. I prefer the use of two H11 opto couplers which
> work
> perfect. On the receiving end the diode along with a current limiter and
> blocking diode for the negative level works perfect. On the output side a
> power source is needed. If one uses an USB adapter it does have the + 5
> volt
> which again works perfect. How ever many prefer to use RS 232 direct and
> that is why I hope to get some comments and suggestions from the list.
> Corby
> used on our counter circuit that he described a separate power source.
> Present MAX circuits use a + 1.4 volt threshold but considering legacy the
> question is what should the voltage swing be to make it compatible for
> most PC's and what options exist to get the necessary voltage. In the past
> other pins on the RS 232 port where an ideal power source. Still an
> option?
> Bert Kehren
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
More information about the Time-nuts_lists.febo.com
mailing list