Getting the DS18B20 detected and temperature read
Vdd on the DS18B20 is not connected to anything.


According to the datasheet:


  When the DS18B20 is used in parasite power mode, the VDD pin must be connected to ground





  Connect 5V from the Arduino to both DQ from the DS18B20 and Port 2 on my Arduino (the two yellow cables).


That means port 2 would always be high, right?



According to Temperature Sensor DS18B20 this is the wiring for non-parasitic power:



If you want the two-wire version (parasitic power) it would be: