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1  Forum 2005-2010 (read only) / Interfacing / Arduino and 1-wire not working with +16 DS18B20's on: June 19, 2008, 02:05:07 am
Hello everyone,

I am from Irvine,CA. I am working with a network of 1 wire temp sensors. (DS18B20).

have you ever tried using your 1-wire arduino and Jim's updated library for arduino-10 with more than 9 DS18B20's in parasite power mode?

I am using your  example code and the 1-wire library by calling it from the Arduino IDE as someone has posted in the arduino playground.( I have even commented the code)

I am attempting to connect 29 DS18B20's in parasite power mode. So far I have tested those 29 individually with your library and they worked pretty well. I can discover their addresses and ask them for a temperature value.

As long as I connect  8 DS18B20 to the same wire of course, the readings become rubbish. Only two sensors keep giving me their ID and loop forever(CRC's ok). The others sensors seem to be lost or not being able to be discovered ever.

It is not a power issue since I have looked at the signal over the oscilloscope. It is neither a problem of the pull up resistor.

I got 100 DS18B20's from maxim. ALL OF THEM WORK PERFECT INDIVIDUALLY.

The weird behaviors comes into play when I CONNECT MORE THAN 8 sensors. I tried replacing sensors with those hundred I got until I find one that is is able to be read adding an extra sensor to the 8 sensor network. The farthest  I could go was 16 sensors. Leaving 16 sensors cataloged as not being able to participate in a network of more than 8 sensors.

this means that If I have a network of 16 DS18B20's working well (after trying with ~32 different sensors until 16 worked ok together) and I replace one of them with one of the cataloged as "bad"(~15) all the information becomes rubish again.

I am pretty much sure is a software problem( the 1-wire library).

Can you provide any help?

Many thanks,.

Ulises
 :-[Irvine, CA.
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