DS18B20 reading wrong value [solved]

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bennybubble
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DS18B20 reading wrong value [solved]

#1 Post by bennybubble » 13 Feb 2016, 17:24

Hi,

I've a DS18B20 connected to GPIO-2 of a ESP01 with R78 installed but the reading is wrong :

1 Temperature - DS18b20 sensor 28-ee-e9-12-3-0-0-d6 12 GPIO-2 Temperature: 30.69

Expected temp is ~20 C, moving the DS18B20 to an ESP12 (GPIO-14) gives proper results, any idea how come ?

And YES a 4k7 is connected between Vdd and DQ as well as IDX has a non-zero value (on both ESP01 and ESP12).
Also tried GPIO-0 with same negative results.
Does it have something to do with the I2C scan at powerup ?

Second question, is a DS1820 supported as well or only DS18B20 ??

-ben
Last edited by bennybubble on 18 Feb 2016, 10:52, edited 1 time in total.

leszektg
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Re: DS18B20 reading wrong value

#2 Post by leszektg » 14 Feb 2016, 15:28

You soldering DS18b20 directly to ESP? Esp heats up, it shows higher temperature

leszektg
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Re: DS18B20 reading wrong value

#3 Post by leszektg » 14 Feb 2016, 15:29

You soldering DS18b20 directly to ESP? Esp heats up, it shows higher temperature

bennybubble
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Re: DS18B20 reading wrong value

#4 Post by bennybubble » 14 Feb 2016, 18:50

Nice thought but not anymore after 10 minutes ...
DS18B20 should give ~ 20 C.

-ben

tozett
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Re: DS18B20 reading wrong value

#5 Post by tozett » 14 Feb 2016, 19:55

maybe something with the GPIO2, wich is TXD1
as an INPUT not so easy?

want to check this info?:
http://www.forward.com.au/pfod/ESP8266/ ... index.html

bennybubble
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Re: DS18B20 reading wrong value

#6 Post by bennybubble » 16 Feb 2016, 16:48

Hi,

Good information! But in case of a DS18B20,GPIO-2 already has an external pull-up of 4K7 and is not pulled to ground during booting (as far as I know).
Couldit be realte to an initial I2C scan or is this not done on GPIO-0 / GPIO-2 ?

I'm planning to use the ESP01 in a PIR sensor and would like to add a temp sensor to it to measure the temp inside, just for fun !

Any good working alternatives (for a temp a sensor) ?

-antoon

tozett
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Re: DS18B20 reading wrong value

#7 Post by tozett » 16 Feb 2016, 18:38

Two esp01 ?
;)

bennybubble
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Re: DS18B20 reading wrong value

#8 Post by bennybubble » 17 Feb 2016, 10:47

:D Good idea !

Only problem is that I cannot even get a single Ds18B20 to work on a ESP01 ...
Neither on GPIO-0 or GPIO-2.

-Ben

bennybubble
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Re: DS18B20 reading wrong value

#9 Post by bennybubble » 18 Feb 2016, 10:52

It turned out that my ESP01 was bad, now using a 'fresh' one and all ok !

tozett
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Re: DS18B20 reading wrong value [solved]

#10 Post by tozett » 18 Feb 2016, 11:16

SOLVED
(in one page) :)

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