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Can this DS18B20 sensor be used with Arduino internal pull-up or it require exactly 4.7k pull-up resistor?

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The Arduino internal pull-up is something like 50k. That is a lot different from 4.7k. You would probably find that the pull-up is not strong enough to get clean pulses from the device. Also if you are using it in one-wire (parasitic) mode notice this from the datasheet:

To assure that the DS18B20 has sufficient supply current, it is necessary to provide a strong pullup on the 1-Wire bus whenever temperature conversions are taking place or data is being copied from the scratchpad to EEPROM.

Notice the words 'strong pullup'. The internal pullup is not strong.

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  • Yeah you are right. Also I find out that these internal pull-ups depends also from type of Arduino (Uno, Nano, Mega etc.) so they have different values as well.
    – ShP
    Feb 4 '17 at 2:47
  • It varies from chip to chip in the same family, and even pin to pin depending on what other functions the pin has. Last time I measured them on a range of chips they varied from about 25k to 40k
    – Majenko
    Feb 4 '17 at 10:32
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If the datasheet specifies a 4.7kΩ resistor then a 4.7kΩ resistor is what you need.

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    Do people not like the fact that the datasheet knows best? They don't put these things in datasheets for fun you know.
    – Majenko
    Feb 3 '17 at 19:55
  • 4.7kΩ is a great starting point, but you should choose differently depending on your supply voltage. At 5V with 4.7kΩ pullup, the device has to sink about 1mA to pull the line low. If instead you're operating at 3.3V you should use 2.7kΩ to sink the same current. Apr 7 '21 at 1:19

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