>
> Along the same line I am now wanting to add more 1820s to the system but
> have hit a snag.  I read the 64 bit serial number from several devices and
> put  a "Match Rom (55h)" command in the program to select the chip I want to
> read.  The problem is that the micro doesn't always read the addressed
> device when there is another 1820 on the line.  I have a couple of 1820s
> that will work together but others, including my outside device, won't work
> at all with a second device on line.  All devices work fine by themselves
> even though they still must match the serial number.
>
> Any ideas?

> Rod Phillips schrieb:
>
> > Hello to all,
> >
> > I am using a DS1820 to measure outdoor temperature, and get a large
> > difference when supplying 5v to the device as opposed to operating on
> > parasite power.  Without the 5v the temperature reading is about 5 degrees
> > (F) lower - this morning 3 above with 5v and 2 below without it.  I am using
> > about 60 feet of Cat. 5 cable. The reading with 5v connected is the correct
> > reading.  Any ideas?
> >
>
> I had the same problem on a Cat.5 cable of 100 feet length.
> My solution was:
> Supply +24V over the cable and have a 5V Lin.Regulator at the end where the
> sensor is.
> Peter
>
> >
> > Along the same line I am now wanting to add more 1820s to the system but
> > have hit a snag.  I read the 64 bit serial number from several devices and
> > put  a "Match Rom (55h)" command in the program to select the chip I want to
> > read.  The problem is that the micro doesn't always read the addressed
> > device when there is another 1820 on the line.  I have a couple of 1820s
> > that will work together but others, including my outside device, won't work
> > at all with a second device on line.  All devices work fine by themselves
> > even though they still must match the serial number.
> >
> > Any ideas?
>
> No, but I am interested.
>
> >
> >
> > Rod