[time-nuts] RS 232

paul swed paulswedb at gmail.com
Thu Jul 25 10:21:20 EDT 2013


Debating the band belive ideal for older is +-3V. But I would need to
check. And how old is old? Not to sure many of the old 1488 1489 devices
are around anymore.
I think more compatibility would be supported by the +-1.4 you mention.
Regards
Paul
WB8TSL


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
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