On Tue, Dec 09, 2003 at 06:04:19AM -0800, Edi Im Hof enlightened us
thusly
>
> Hi all
>
> The RS485 is defined to a maximum lenght of 1200m at 400kbps. I don't
> need 400kbps, but up to 2500m of cable. Is it possible to extend to
> this lenght with 9600bps?
Yes. I would feel that cable quality would be important. The phones use
twisted pairs to eliminate crosstalk over long distances.
>
> Are there other standards for data transmission?
Zillions. Network, usb, opto, & ieee1394 transmissions spring to mind as
alternatives, but I'm sure to get shot down for saying that.
> I have two wires
> (plus power and ground), one master and up to 20 slaves. The maximum
> distance between two slaves is 500m. A multimaster bus would be nice,
> but is not a must.
>
> The network should also work if the cable is broken (up to the break).
> With RS485, I would switch the termination with a relais.
There is the 'paperwork'side of this: Once you depart from the standard,
your design will have to be tested more thoroughly by standards bodies
(e.g CE approval testing) than if you are doing it by the book. The
question of EMI also surfaces.
>
> What else... Oh yes, the system is battery powered and should work
> fron 25�C to -40�C.
>
> Any ideas?
>
> Edi Im Hof
>
I'm intruiged by the temprature range. -40 I can imagine if your
backside is frozen but how come it doesn't go above 25�C?
--
With best Regards,
Declan Moriarty.
--
Author: Declan Moriarty
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