Arduino interfacing of Four DS18B20 with 10m long probe interfacing

Other Hardware Sensors
1

Hi guys,

I wish to interface 4 numbers of DS18B20 one wire Temp sensor with 10 meters probe each to arduino on common one wire line. What should be pull up resistor value ?
How to take care of four numbers of 10m long probes?
What type of cable to be used ?
What precautions shall I take ?

2

10M, I2C no way.

You do know the DS18B20 doesn’t use I2C ?

:wink:

3

4.7K is the usual that I have seen with no mention of any difference depending on buss length.

I am not sure what that means. Can you, please, elaborate?

4

Updated post.
Please help for four numbers of 10 meters long probes

LarryD 5

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1 Like
6

For four numbers of 10meters long probe shall I use 2.2k pull-up or standard 4.7k will do the job satisfactorily ?

7

4.7k is recommended, nothing happen if it will be 2.2k

Do you mean 4 cables, 10m long each?

8

Yes , 4 cables , each 10meters long fitted with DS18B20

9

4 cables , each 10meters long fitted with DS18B20.
Anything I am missing regarding interfacing ? Or is it straight forward circuitry.

10

I’ve done three (3) ~30 foot cable lengths like this no problem, @ 2.7k.

Try 4, report back what results you get.

11

Cables should have exact same length, diff. less than 2.5cm.

12

I'm using 21 DS18B20 on a 15m long wire. I had to reduce the pullup-resistor to 2 kOhm to make it work reliable.

You have to use a linear bus-topology.
This means one long cable with as short as possible stubs connecting the DS18B20-sensors
do not use a star-topology

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The reason is that with a star-topology you will have too much electrical reflections which will bend the signal too much so you don't get valid readings.

don't place your microcontroller in the middle if the sensors are physically east west north south.

Even with a 40m long line-topology with 10cm short stubs to each DS18B20-sensor where you place the microcontroller near to one sensor (for example north) and then the one loooong wire goes from north to west to south to east the signal-quality will be better than with placing the microcontroller in the middle and use 4x 10m star-topology

best regards Stefan

13

To elaborate on @StefanL38 and @Budvar10 have suggested:

The designers of the 1-wire devices advise that a star topology is the hardest to get to work reliably. The reasons include reflections and impedance mismatch that are hard to control.

An alternative, if you have the pins available, would be to create 4 linear topology networks.

14

Some long line info:
https://www.analog.com/en/technical-articles/guidelines-for-reliable-long-line-1wire-networks.html

https://www.hacktronics.com/Tutorials/arduino-1-wire-tutorial.html

http://sheepdogguides.com/arduino/DS18B20-HowTo.htm

15

F-Secure reported that the hacktronics website is dangerous

So I made an online-scan
The result is that the used PHP is outdated

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best regards Stefan

16

First I've heard, TNX.

17

@JCA34F
That article from Analog Devices is helpful the most.

18

Did you follow any topology of physical connections ?

19

As mentioned in post #12.

20

Noted. I will prepare a 40m long cable with stub points in between.