Getting the DS18B20 detected and temperature read

Question

I'm quite new with the electronics part of Arduino, but I thought that this was the basic way to get the DS18B20 temperature device hooked up. However, I can't detect it in my program using OneWire and DallasTemperature.

This is an image of my connections:

enter image description here

Basically my approach was like this:

Connect ground on ground on the DS18B20. Connect 5V from the Arduino to both DQ from the DS18B20 and Port 2 on my Arduino (the two yellow cables). Between the 5V and the two yellow cables, I connected a 4.7K resistor. Vdd on the DS18B20 is not connected to anything.

Anyone have any idea why this is not working as expected for me?

Thanks in advance!

• Nick Gammon: I can't see the DS18B20 in your picture. Can you please sketch up (eg. on paper) your wiring? I can't quite follow your description.

Answer 1

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

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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?

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

Non parasitic power

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

Parasitic power

• Øyvind Bråthen: I didn't get the parasitic power version to work, but the top image explained how the rasistor should be placed in the non-parasitic version, and that did the trick! Thanks a lot!
• Nick Gammon: Glad it worked. The design is the standard "open drain" concept where the output is "pulled high" by the resistor, and the device drives it low when it wants to output a zero. This allows multiple devices to share that wire because it doesn't do anything any harm if multiple devices drive it low at the same time.