DS18B20 external supply ?

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bianchi77
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Posted by bianchi77: Mon. May 9, 2016 - 10:13 PM
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Guys,

 

I have a question about DS18B20 external supply, when I connect DS18B20, why is the circuit short ??
I connect DQ to PC0 on atmega128....what's wrong with it ?

 

Thanks

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AVR Microcontrollers, megaAVR and tinyAVR
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Kartman
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Posted by Kartman: Tue. May 10, 2016 - 12:12 AM
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This question makes little sense. Stop and think for a moment what you're asking. I we were standing next to you we could probably understand, but we're not. You need to give us more informatiom - like how you've connected the ds1820 and how you're measuring it.
If there is a short circuit, sounds like something is wrong.

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DocJC
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Posted by DocJC: Tue. May 10, 2016 - 01:57 AM
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A schematic or a good photo of the setup would be helpful.

 

JC

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bianchi77
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Posted by bianchi77: Tue. May 10, 2016 - 02:10 AM (Reply to #3)
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DocJC wrote:

A schematic or a good photo of the setup would be helpful.

 

JC

Ok I ll post schematic later on... when I tested pin 1 and 3 18b20 without it..not short.. I don t get it??

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Bronze Markawneil
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Posted by awneil: Tue. May 10, 2016 - 07:39 AM
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Have you studied the DS18B20 datasheet to see how it should be connected ?

 

Does your setup match what the datasheet says?

 

Note that there are 2 ways of powering the DS18B20: either with a separate power connection, or using so-called "parasite power" - it's all detailed in the datasheet.

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bianchi77
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Posted by bianchi77: Tue. May 10, 2016 - 09:05 AM (Reply to #5)
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Yes I have read them....

Here's the schematic:

 

Any ideas ?

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Kartman
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Posted by Kartman: Tue. May 10, 2016 - 10:02 AM
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Have you tried another port pin?

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bianchi77
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Posted by bianchi77: Tue. May 10, 2016 - 11:01 AM (Reply to #7)
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I will, but I've made a track for this DS18B20 on my PCB....

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DocJC
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Posted by DocJC: Tue. May 10, 2016 - 03:18 PM
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Please describe again exactly what the circuit is doing, and what you expected it to do.

 

JC

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bianchi77
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Posted by bianchi77: Tue. May 10, 2016 - 10:22 PM (Reply to #9)
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ATmega128 will read temperature information from DS18B20 via PC0.....when I try with module, it's working but when I put on PCB track, it becomes short, I don't get it ??
 

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DocJC
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Posted by DocJC: Tue. May 10, 2016 - 11:46 PM
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I think you ought to recheck the orientation of the DS on the PCB, recheck the PCB routing, and look closely for any solder bridges, etc.

 

If you remove the DS from the PCB does the micro run correctly?

 

If the DS is not installed, is there a short between the traces, when measured with a DMM, and the board not powered up?

 

JC

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bianchi77
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Posted by bianchi77: Wed. May 11, 2016 - 02:05 AM
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Yes it s working without ds18b20 i can see 4k7 resistance when it s fitted
I don t put any resistors..??

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DocJC
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Posted by DocJC: Wed. May 11, 2016 - 12:10 PM
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Do you have an Arduino or a breadboard with which you could try that particular DS, and make sure it is still good, separate from your main PCB?

 

JC 

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