Re: Re: 1-Wire Headache

[Stuart Poulton <stuart.poulton@xxxxxxxxxxxxxx>]

Hi Marc,

I suspect that the problem is that the comm port can't provide the
required current.

I see that it's possible to provide the temp08 with a 12V supply via the
screw terminals, I'd recommend doing this. I've stayed away from
parasitic power where ever possible with 1-wire and have found the
results to be very promising.

Cheers

Stuart

On Wed, 2007-07-18 at 11:27 +0000, marcrfuller wrote:
> Hi Quinten,
>
> The sensors are DS18B20's
>
> If I understand the term parasitic power correctly then yes they are
> using parasitic power - e.g the power is taken from the TEMP08 via the
> comms line.
>
> Cheers,
>
> Marc
>
> --- In ukha_d@xxxxxxx, Quinten Uijldert <yahoogroups2@...>
wrote:
> >
> > And another question is if you are using parasite power or not? 
And
> > what Dallas sensors they are?  DS1820 or DS18S20?
> >
> > On 17 Jul 2007, at 19:42, Stuart Poulton wrote:
> >
> > > Marc,
> > >
> > > 85c is the reading that is returned as an error, normally
that a
> > > conversion wasn't able to be made.
> > >
> > > 2 questions
> > >
> > > 1 - Are you making connections to all 3 legs of the sensors
?
> > > 2 - What sort of cabling are you using.
> > >
> > > I've successfully run 1-wire over 100m of cat5, using
modules that
> > > daisy chained (modules of my own design)
> > >
> > > Cheers
> > >
> > > Stuart
> > >
> > > On 17 Jul 2007, at 17:49, Marc Fuller wrote:
> > >
> > >> Hey Guys,
> > >>
> > >> Just bought myself a TEMP08 to replace my Quasar logger.
It's all
> > >> up and
> > >> running and 3 of the sensors are working perfectly. My
problem is
> > >> with
> > >> the fourth.
> > >>
> > >> For some reason the fourth sensor that is at the end of
the bus,
> > >> keeps
> > >> showing a temperature of 85c, which is obviously not
correct.
> > >> Occasionally it will show the correct temperature, but
mostly it
> > >> shows
> > >> 85c. I replaced the probe with a new one and am getting
the same
> > >> thing !
> > >>
> > >> Now I must admit I don't totally understand 1-wire yet..
this is my
> > >> first proper jump into it. So it could be that I have
set up the bus
> > >> incorrectly ? or what else is likely to cause this
problem ?
> > >>
> > >> The probes are wired in series and the farthest one is
only about 10
> > >> meters away.
> > >>
> > >> Anyone got any ideas ? Could I just be really unlucky
and have two
> > >> probes shorting out ?
> > >>
> > >> Any help appreciated
> > >>
> > >> Marc
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >
> > >
> > >
> > >
> > >
> > >
> >
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