Temperature reading from sensors in the silo (DS18b20 + ESP8266).

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1shot2killz
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Temperature reading from sensors in the silo (DS18b20 + ESP8266).

#1 Post by 1shot2killz » 10 May 2022, 09:30

Hi,
I have a problem with connecting DS18B20 sensors.
The company has silos with DS18B20 sensors installed according to the manufacturer. At present, the temperature readings (9 sensors per silo) are read from the hand-held reader (photos).
There is a 3-core cable with a thickness of 0.75mm2.
After plugging in the reader (powered by an R9 - 9V battery), 5V appears on the terminals - +, it supplies the sensors, and the third cable is probably DATA. The distance between the reader and the last detector can be about 100m.
Unfortunately, when I connect it to ESP8266, it does not see the sensors. When I plug in the sensors, I have the correct reading for a short time (PIN D4)
I powered the sensors directly from the 3V board and connected the reader and terminals - + released 5V and connected Data to ESP (PIN D3).
I also noticed when I plug the DATA cable into PIN D3 the diode starts to glow constantly.
Unfortunately, I can't get to the sensors to check them.
Do you have any advice on how to start it?

https://photos.app.goo.gl/UmJaQzednnNm6daT6

Build: ESP_Easy_mega_20210802_normal_alt_wifi_ESP8266_4M1M

TD-er
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Re: Temperature reading from sensors in the silo (DS18b20 + ESP8266).

#2 Post by TD-er » 10 May 2022, 09:39

See also the (outdated but still useful) Wiki documentation: https://www.letscontrolit.com/wiki/inde ... as_DS18b20

As you can see, the Dallas sensors need a pull-up resistor between the + and data.
GPIO-0 (D3) you're using does have a pull-up resistor, but that one might be of too high resistance.
Also GPIO-0 is probably not the best one to use as it also is used to enter flash mode if it is pulled down during boot.

Perhaps the hand meter you're using does have an internal pull-up resistor, which isn't there when connected to the ESP?

Normally I would advise against using 5V, but since you're using such a long cable, I guess it may improve stability here.

1shot2killz
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Re: Temperature reading from sensors in the silo (DS18b20 + ESP8266).

#3 Post by 1shot2killz » 10 May 2022, 09:57

The resistor is 4.7k Ohm.
Do you think that 3V power supply straight from the board should also be enough? The ESP board is powered by a 5V 2.4A power supply.
One more thing puzzles me and I don't know what that means. When I plug in the DATA cable from the sensors even without power supply in GPIO-2 (D4), the LED on the board lights up constantly.
So which GPIO will be the best?
https://photos.app.goo.gl/GCc8DwA4CRUWpCwH7

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Ath
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Re: Temperature reading from sensors in the silo (DS18b20 + ESP8266).

#4 Post by Ath » 10 May 2022, 12:25

Please add your screenshots as attachment in the forum, external links tend to expire after some time, and are not shown in-line.
/Ton (PayPal.me)

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Re: Temperature reading from sensors in the silo (DS18b20 + ESP8266).

#5 Post by TD-er » 10 May 2022, 13:19

I don't know why the LED lights up.
Perhaps you're powering the board via the 5V on that pin?
Most overvoltage protection on microcontrollers is done by a diode to the VCC.
Thus you're effectively powering the VCC pin of the ESP.

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