Arduino Forum

Using Arduino => Sensors => Topic started by: Igor1024 on Jan 30, 2011, 04:09 am

Title: DS18B20 wrong connection
Post by: Igor1024 on Jan 30, 2011, 04:09 am
I've tried to connect this thermometer to Arduino Duemilanove like there http://stuff.nekhbet.ro/2009/08/23/how-to-use-the-ds18s20-and-ds18b20-temperature-sensors-with-arduino.html (http://stuff.nekhbet.ro/2009/08/23/how-to-use-the-ds18s20-and-ds18b20-temperature-sensors-with-arduino.html), and used program from there (first listing )http://tutorialpedia.org/tutorials/Working+with+Dallas+DS18S20+and+DS18B20+temperature+sensors+from+Arduino.html (http://tutorialpedia.org/tutorials/Working+with+Dallas+DS18S20+and+DS18B20+temperature+sensors+from+Arduino.html), but it doesn't find thermometer.
That's the way I connect it (perhaps I'am wrong in some trinket):
http://saveimg.ru/show-image.php?id=631b3bf3a2e58c887e7b43b5ea4e372e (http://saveimg.ru/show-image.php?id=631b3bf3a2e58c887e7b43b5ea4e372e)
Title: Re: DS18B20 wrong connection
Post by: Fe2o3Fish on Jan 30, 2011, 09:16 am
You have incorrectly wired your 18S20.  See figure 4 on page 6 of the manual
for the DS18S20.   The Ground and Vcc pins need to be shorted together and
connected to ground.  The Data pin goes to the digital pin on the Arduino as
well as thru a 4K7 resistor to Vcc.

The diagram on stuff.nekhbet.ro is not completely correct.

   -Rusty-
Title: Re: DS18B20 wrong connection
Post by: Igor1024 on Jan 30, 2011, 09:58 am
Sorry for stupid question, but what "Vpu" is? 
Title: Re: DS18B20 wrong connection
Post by: Igor1024 on Jan 30, 2011, 10:03 am
It works. Thanks!
Title: Re: DS18B20 wrong connection
Post by: Fe2o3Fish on Jan 30, 2011, 09:27 pm
Vcc is the positive supply voltage.   The 18S20 max's out at about +5.5-volts.
Glad you got it working!
Title: Re: DS18B20 wrong connection
Post by: Igor1024 on Jan 31, 2011, 04:31 am
I know about "Vcc".
What's "Vpu"? Is "Vcc" the same thing?
Title: Re: DS18B20 wrong connection
Post by: Fe2o3Fish on Feb 01, 2011, 07:59 am
I've never heard of Vpu.  Where are you seeing this??   A little
context would helpful.
Title: Re: DS18B20 wrong connection
Post by: Igor1024 on Feb 01, 2011, 10:30 pm
At page 4 of DS18S20 manual (figure 4).
Title: Re: DS18B20 wrong connection
Post by: Fe2o3Fish on Feb 02, 2011, 08:32 am
Vpu is the pull up voltage supply used on the data line for "talking"
to the DS18S20.  Technically, it's not the same thing as Vcc but it
can be (well, in the spec' sheet, the supply voltage is Vdd, not Vcc).

Check out the DC Electrical Characteristics table on/about page 20.

    -Rusty-