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, <[email protected]> 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 -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
