ESP8266 Community Forum

- Sun Aug 28, 2016 5:39 am #53967 Is there a (practical) limit to the number of DS18B20s that can be connected to pin 2 and read with the TEMP() function?

Phil

- Sun Aug 28, 2016 11:18 am #53987 I don't know of any hard limit except what the one wire buss will support.

Only used 3 or 4 when I was testing.

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- Sun Aug 28, 2016 12:43 pm #53994

Is there a (practical) limit to the number of DS18B20s that can be connected to pin 2 and read with the TEMP() function?

Phil

If i understand the concept of the DS18B20s there shouldn't be a limit from the sensor itself,
however it uses basically a Onewire protocol , I didn't took a look in the libary for the DS18B20s if there isnt a max specified there it should be good.

I recall a project conducted at my school with the Sensor they linked up about 30 of them, it worked, however the length of the wire is the problem , A lower pull-up resitor will help provide you a bit more length but generally i would keep it depending on the type of wire u use under the 5 - 8 meter range.

Kind Regards,

Orcanbull

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- Mon Aug 29, 2016 12:11 pm #54076 That's excellent news.

Can you tell me how the individual ICs are assigned to the index numbers? Are they randomly assigned (in which case it's going to be very difficult to know which is which!) or in alphabetical order of serial number? Or what?

It would be very helpful to have a function that returns the serial number of any particular DS18B20. eg

Code: Select allsn$ = srl_temp(n)

Any chance?

Phil