Connecting the ds18b20 | Pull-up resistor needed?

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garnold
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Connecting the ds18b20 | Pull-up resistor needed?

#1 Post by garnold » 17 Jun 2019, 14:40

I was wondering if a pull-up resistor is needed when connecting the DS18B20 to the NodeMCU. I stumbled upon an article that shows that you can eliminate it and was wondering if others have had success. I have not had the chance to test this (been rather busy with the day job) but will once I get the chance.

Article -
https://wp.josh.com/2014/06/23/no-exter ... mp-sensor/

Dick60
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Re: Connecting the ds18b20 | Pull-up resistor needed?

#2 Post by Dick60 » 19 Jun 2019, 20:49

I have to 18b20 in use already for a long time and yes I use a pull-up resistor. without it was not stable or sometimes it did not work. Advise from me, use a resister to prevent troubles! :D

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ThomasB
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Re: Connecting the ds18b20 | Pull-up resistor needed?

#3 Post by ThomasB » 19 Jun 2019, 20:51

The article mentions that the data line pullup resistor can be omitted in special circumstances (Low Dallas device count, short cable lengths). It's a solution that uses the ESP module's programmable internal weak pullup (~50K ohms) that can be enabled on a I/O pin. Ideal for those users that want to save $0.01 USD (1 penny).

However, ESPEasy's DS18B20 plugin does not enable the internal weak pullup resistor. So spend the extra penny and install the external 4.7K ohm value that is recommended by Dallas.

- Thomas

garnold
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Re: Connecting the ds18b20 | Pull-up resistor needed?

#4 Post by garnold » 21 Jun 2019, 03:16

Good deal. I have a resistor installed and it's working fine. The only real reason I was looking towards this is because of saving space on my perf board. I'm using one of those little dev Wemos D1 Mini shields that lets you build on. Not a heck of a lot of room there :o :o :o

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