No worries.

As someone else alluded to, be careful with current
requirements....while you'll have no trouble "seeing" all 35 devices on
the 1-wire network, issuing a temperature convert command to all 35 at
once will get you into trouble. Assuming that you don't need terribly
speedy response time, you can just have your code cycle through each
sensor.

Or, you can beef up power on the 1-wire network with an additional +5vdc
line, or with a capacitor and Schottky diodes.

-marc

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
Of mmynsted_news
Sent: Monday, September 06, 2004 6:50 PM
To: Microcontroller discussion list - Public.
Subject: Re: [PIC:] shift register(s) to read temp from 35 DS1820
basedsensors

LOL!  Thank you.

OK.  Originally I was going to use LM34s (maybe they may be networked
too, I=20
will check.).   The same idea is still of interest to me though, because
I=20
know that I will encounter this same problem. (I will check=20
http://www.maxim-ic.com/ for their other sensors too, this 1-wire design
is=20
obviously really nice.


--
MM

On Monday 06 September 2004 5:20 pm, Marc Nicholas wrote:
> Hi...
>
> You've totally lost me here....you only need 2-wires (GND + signal) to
> read all 35 sensors -- that's the idea of the 1-wire bus that Dallas
> developed; it's a mini network.
>
> Or am I missing something here?
>
> -marc
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of mmynsted_news
> Sent: Monday, September 06, 2004 5:59 PM
> To: piclist@mit.edu
> Subject: [PIC:] shift register(s) to read temp from 35 DS1820 based
> sensors
>
> I am new to this, and a hobbyist, not an EE, so would anybody
recommend
> a
> shift register compatible with a PIC 16F628 based design that could be
> used
> to allow me to read temp from about 35 DS1820 sensors on as few I/O
pins
> as
> possible? =A0The idea is I know that I will need to deal with more I/O
> than I
> want to have built-in to my PIC. =A0Reliability, and low power
consumption
> are
> far more important than speed, if that makes any difference. =A0Has
> anybody
> done something like this? =A0(I do not want to use a handful of small
> shift
> registers, I would rather find one larger chip.)
>
> If I look at a site like www.mouser.com and search for shift register
I
> get
> many results. =A0I suspect I would want to limit by DIP, and 8 bit too,
> but
> that still leaves many options.
>
> --
> MM
>
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