On Tue, Dec 09, 2003 at 07:44:19AM -0800, Edi Im Hof enlightened us
thusly
> At 07:24 09.12.2003 -0800, you wrote:
> >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.
>
> None of them works with 2500m on a bus...
>
As others have said (I'm not familiar with rs485 - I've been chewing on
different stuff lately) repeaters seem to be the way to go.
As compatability isn't an issue, you could roll your own standard -
preferably current based. A trick I liked here was Manchester coding -
send a sinewave and reverse the phase to change state.
> >
> >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?
>
> It's used in a glacier in the antarctic. The ice is about 0�C in a
> depth of 2500m and arround -40�C on the surface. I have to test the
> units in the office and I don't like to cool it down to 0�C or go to
> the climate chamber for every test...
That explains a bit, all right.
--
With best Regards,
Declan Moriarty.
--
Author: Declan Moriarty
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