Read scratchpad is pretty darn fast. I'd have to go back to my notes to see
exactly how fast. If I remember correctly, the convert will take something
like 1mA per device during conversion.
You can also take turns with bunches of devices, reading a smaller subset
so as to optimize load on the bus. I started a thread on this previously.
You can issue a few tens of converts in succession, then go back and read
scratchpads of the devices you like.
C
On Wed, Oct 1, 2014 at 12:14 PM, Roberto Spadim <robe...@spadim.com.br>
wrote:
> here using usb-serial isnt a problem
> but if i remember some linux usb-serial drivers have a limit of
> howmany devices/computer could be used
> maybe it' near to 16usd/computer (per linux operational system)
>
> 2014-10-01 16:13 GMT-03:00 Roberto Spadim <robe...@spadim.com.br>:
> > :) probably yes
> > but any problem including more buses devices?
> >
> > 2014-10-01 15:57 GMT-03:00 Jerry Scharf <sch...@lagunawayconsulting.com
> >:
> >> Roberto,
> >>
> >> I was planning on a large power supply and using simultaneous mode, but
> >> from my prior experience we still wouldn't be able to poll the
> >> temperature of all the devices very quickly. Thus the need for more
> >> buses to run in parallel.
> >>
> >> jerry
> >>
> >> On 10/01/2014 11:53 AM, Roberto Spadim wrote:
> >>> hummm you need to measure, or check a alarm condition?
> >>>
> >>> with 300 using alarm condition is possible only alarmmed sensors will
> >>> be reported at bus, it's not temperature convertion it's only alarm
> >>> information (alarm on/off)
> >>>
> >>> measuring temperature you should use (i don't remember the owfs file
> >>> name) a option to convert all sensors at same time, but ensure a good
> >>> power supply and after read one by one without convert temperature
> >>> (the same owfs file do this)
> >>>
> >>> 2014-10-01 15:04 GMT-03:00 Jerry Scharf <
> sch...@lagunawayconsulting.com>:
> >>>> Hi,
> >>>>
> >>>> I am looking at using 18b20s to measure some load resistors and a
> couple
> >>>> other things. This is for a large bank of unit under test. The thing
> is
> >>>> that there are 300 load resistors plus 20-30 other channels to track.
> >>>> Then again, if we do a second monitor point, that's another 300
> sensors.
> >>>> >From my experience with 30 sensors, having 300 is going to take a
> number
> >>>> of buses to be able to poll in finite time.
> >>>>
> >>>> How many buses make sense? What type of bus masters should I choose?
> We
> >>>> will have some type of monitor computer, probably a linux box.
> >>>>
> >>>> thanks in advance,
> >>>> jerry
> >>>>
> >>>>
> >>>>
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> >>
> >>
> >>
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> >
> > --
> > Roberto Spadim
> > SPAEmpresarial
> > Eng. Automação e Controle
>
>
>
> --
> Roberto Spadim
> SPAEmpresarial
> Eng. Automação e Controle
>
>
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