Dallas 18B20 for cold junction mod

I would like to share my experience with the Dallas 18B20 sensor available from lots of sellers e.g. on Amazon. You might think 18B20 is 18B20, just as I did. But that's not the case: the Dallas 18B20 does not provide the 1-wire mode the Maxim 18B20 does. Therefore the cold-junction mod as described in the Wiki does not work with the Dallas. Fortunately the Dallas type can be used anyway. You just have to run the sensor with external supply voltage. One easy spot to get a 3.3V supply for the senosr is in front of the ISP header. There are two tracks on the PCB where the outer one is GND and the inner one is +3.3V.

The pins of the Dallas sensor are GND - Data - VCC from left to right when looking onto the flat side with the label.

So the cold-junction mod using the Dallas 18B20 goes as follows:

• remove a bit of the green solder mask to free the 3.3V copper track in front of the ISP header and put a bit of solder there
• solder a piece of wire to the VCC pin of the sensor
• solder a piece of wire to the DATA pin, same as in the original mod
• solder the GND pin of the sensor to ground on the PCB, same place as in the original mod
• add the 4k7 resistor - a regular non-SMD type also works, by the way - and connect the DATA wire as described in the original mod
• solder the sensor's VCC wire to the spot prepared in front of the ISP header
• you are done!

In the end everything should look similar to this:

Edit: 8-09-2019 by Giorgio I used a DALLAS DS18B20+PAR purchased from Mouser and it works in the 1-wire mode (pin 1 and 3 to GND).