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I want to wire up a few DS18B20 sensors to measure various points across a span of about 10 meters. (I intend to hook this up to an ESP8266 and use Tasmota, but I think that's not really relevant to my question).

I am uncertain if I need to have 1 4k7 pull up resistor for the whole chain of devices, or a 4.7k pull-up resistor for each device (located close to the device).

My google foo is weak, and I've seen both layouts. I could swear that when I worked with these sensors years ago I had 1 resistor per device, but the more I think about it, the less sense this seems to make to me.

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You use one weak resistor (for instance, the data sheet shows a 4.7kΩ resistor) for all the devices in one chain.

The devices use Maxim's "1-Wire" protocol - all devices share a single wire for transmitting and receiving data. To make this work, devices operate in a tri-state mode so that multiple devices don't try to power the wire at the same time. The pull-up resistor is necessary to provide a readable high signal to the CPU.

You can learn more in the DS18B20 data sheet.

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    Thank you for this. I did see the data sheet, but I missed Figure 7 which seems to confirm what you are saying.
    – davidgo
    Apr 28, 2022 at 5:35

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