Thank you Paul. This is exactly what I wanted to know, as I said I already use the opto couplers the only thing is where to get the power from for the transmitting side and you answered that. I will not use it but some others may. I will stay with opto USB.. In a message dated 7/25/2013 4:40:24 P.M. Eastern Daylight Time, paulsw...@gmail.com writes:
Bert I will add back in here. The max232 has the internal switching oscillator and that makes the noise. But you know that. So an external +/-supply linear is cheap and simple. Full wave bridge and 2 caps. No regulation needed. Using your opto isolator provides complete noise and electrical isolation. Computers are nasty beasts especially when you grab +/- power from the rs232 port. Some one re-confirmed my thinking that the rs 232 spec was +/-3V for noise margin. I think thats about all there is. Sorry if I am misunderstanding your need. Regards Paul WB8TSL On Thu, Jul 25, 2013 at 4:34 PM, <ewkeh...@aol.com> wrote: > Bill > Thank you I am only looking for a solution that is simple in Corby's case > we used a separate power source, but the question is, is it necessary. That > is why I brought it up to the list. Shopping for ideas. > Bert > > > In a message dated 7/25/2013 4:06:03 P.M. Eastern Daylight Time, > wb6...@cox.net writes: > > Hi Bert, > > My attitude is if you are going to provide an RS-232 port then do it > properly (min of +/- 3 volts & max of +/- 25 volts). RS-232 is still a > popular item in the hobby controller world, although USB is gaining > ground. In so far as stability goes, RS-232 is much cleaner and easier > to handle in the micro coding compared to USB. With that said, there is > nothing wrong with providing both, it just makes the coding a bit > harder. If you need long lines and want common mode suppression then > utilize RS-485, a derivative of RS-232. > > You could also use TOSLINK, the fiber optic lines used in the audio > field. The components are fairly cheap compared to other forms of > plastic or glass (more expensive) fiber products. Most products will > handle up to 5 MHz at reasonable distances. If you are careful in > selecting the TX and RX port parts it can go up to 15 MHz at the top > end, especially at short distances. > > Irrespective of all that, the power source has no relationship to the > RS-232 or USB for that matter. > > 73....Bill....WB6BNQ > > ewkeh...@aol.com wrote: > > >I do not understand your question, I am referring to low noise > applications > > like counters for dual mixers or other AV measurements, but also Shera > and > >even Tbolt where external noise should be kept to a minimum. When you > >chase 1 E-14, isolation is key and I always like to err on the cautious > side > >and as I stated we use blue tooth or USB but in the case of USB there > are > >always H11 in the circuit. Some still like to use RS 232 and the subject > came > >up and I have on my boards H11's like on the counter Corby uses but he > >ended up using an external power source and I like to eliminate that > >requirement. David had the right answer using the power that the RS 232 > mouse uses > >out of a DB 9, started looking but I do not have one any more and I can > not > >find any data. > >Bert > > > > > >In a message dated 7/25/2013 2:48:43 P.M. Eastern Daylight Time, > >ma...@non-stop.com.au writes: > > > >Hi Bert, > > > >I am sure your circuit is clear in your head, but would you mind > attaching > >detail? > >You have perked my interest with the "low-noise" keyword ;) > > > > > >-marki > > > >-----Original Message----- > >From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > >Behalf Of ewkeh...@aol.com > >Sent: Thursday, 25 July 2013 11:39 PM > >To: time-nuts@febo.com > >Subject: [time-nuts] RS 232 > > > >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@febo.com To unsubscribe, go to > >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >and follow the instructions there. > > > > > >_______________________________________________ > >time-nuts mailing list -- time-nuts@febo.com > >To unsubscribe, go to > >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >and follow the instructions there. > > > >_______________________________________________ > >time-nuts mailing list -- time-nuts@febo.com > >To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >and follow the instructions there. > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.