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Forum Index : Microcontroller and PC projects : DS18B20 2 or 3 wire?

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Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5129
Posted: 12:08pm 10 Aug 2014
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Hiya

Building a solar hot water controller based on the uMite, and will be using a few DS-18B20 senders. Geoffs SC articles show how the sender can be used in either 3 wire or 2 wire with parasitic power configurations.

Just wondering, if there was any pro/cons for either?

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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atmega8

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Joined: 19/11/2013
Location: Germany
Posts: 727
Posted: 12:17pm 10 Aug 2014
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The datasheet will give you the Answers.
nrtfm

For short distance and one device parasitic power IS ok.
 
Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5129
Posted: 01:09pm 10 Aug 2014
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Yeah that was what I thought. My runs will be up to 3 meters, and there could be a bit of electrical noise on the supply, so I'll use 3 wire.
The best time to plant a tree was twenty years ago, the second best time is right now.
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vasi

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Joined: 23/03/2007
Location: Romania
Posts: 1697
Posted: 03:38pm 13 Aug 2014
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Hi Glenn,

Always a 3 wire cable and a good library, capable of detecting any error on the bus. The only capable one (detecting bus short circuit, sensor absence, bus error - all very important in critical applications like egg incubators) I saw, was written for AVR microcontrollers. I will try to replicate it for PICs when time will permit. Sometime, a very noisy environment will make the temp. readings impossible so you need to take care when routing the bus.
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Zonker

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Joined: 18/08/2012
Location: United States
Posts: 772
Posted: 03:48pm 13 Aug 2014
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Maybe make the run in a fully shielded type cable would help... Also, maybe going to the 5v part might get more distance... I think there might be a repeater IC also... Edited by Zonker 2014-08-15
 
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