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RESISTORS — and use with DS18B20 September 17, 2011

Posted by rik94566 in 1-wire, aquaponic automation, aquaponics, arduino, CAT 5 Cable, DIY aquaponics, DS18B20, indoor aquaponics, indoor gardens, indoor growing, One-wire, sensor, Sensor Hub, Stainless Steel Temp Probe, Temperature Probe.
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In order to read DS18B20 IC’s or temperature probes a resistor is required. The standard one used in almost all work done on breadboard examples are 4.7K ohm. Upon researching work done with 1-wire temp sensing most people are only working with 1 to 2 DS18B20’s and most of this is with breadboards. In a few cases people are using 3 or 4 only. I have found no cases where anyone is working and in production with 5 or more DS18B20 probes. So I think this is somewhat new ground. That being the case, there is a lot written that as you increase the number of DS18B20’s the power draw becomes greater and you need to decrease the resistor size. The common thought is to go to 2.2K ohm resistor. If that does not work the next size to work with is 1.0K ohm. Well this will be my next testing platform. I will be testing both the 4.7K and 2.2K resistors with up to 10 DS18B20 probes to determine what works and what does not work. Along the way I will determine what happens and how it happens and where the breaking points are in the hardware and the sketches. Will be fun stuff.



1. terry king - September 17, 2011

Hi Rik, A related question is wether you are supplying +5 power to the DS18b20’s in a 3-wire configuration or operating in the 2-wire “parasitic power” mode, in which ALL power is provided through the one resistor…

Regards, Terry King
…On the Mediterranean in Italy

rik94566 - September 18, 2011

Terry – I am using a 3-wire configuration with all power being provided by the arduino. I will be working with using external power shortly with a 3-wire configuration. I have individual resistors connected to each DS18B20 probe. I do not know if this is the most efficient way to do it, but it is the direction I have gone with this so far and it seems to be working OK. As I am learning with electronics there are many solutions to solve problems and it seems to me that once people figure a way that works for their application they seem to stay with it until it does not work any longer or a better way is demonstrated to them.

2. Peter Enmore - September 23, 2011

I agree with Terry that you might want to switch to a different resistor.

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