Hello
A few months ago I made a couple of ESP8266 boards (Looky Wifi), many times I had problems with the DS18B20 Sensors.
Now i have a Project where a DS18B20 Sensor is 20 Meters Deep in the Ground, the Reading of this sensor was not possible, i got only Read errors.
At home I connected a DS18B20 sensor to the ESP8266 Board, first with a 2m cable that worked and then with a 70m cable what didn't work.
Then I measured with the osciloscope the signal at the end of the line, as you can see on the Pictures the pullup is way too weak @70m Cable!
Lesson learned
Just want share my experience
DS18B20 Long Cables
Moderators: grovkillen, Stuntteam, TD-er
Re: DS18B20 Long Cables
Thanks for sharing !
Usually they say "NO WAY" and we don't even try to go beyond specs.....
Usually they say "NO WAY" and we don't even try to go beyond specs.....
Re: DS18B20 Long Cables
Ah good to see it is working with a lower value resistor.
I can imagine the Dallas sensor is now running slightly out of specs, with higher current.
Also test it with the cable unrolled, to see if it may also pick up a lot of noise.
Having it rolled up like this may also act as a filter.
I can imagine the Dallas sensor is now running slightly out of specs, with higher current.
Also test it with the cable unrolled, to see if it may also pick up a lot of noise.
Having it rolled up like this may also act as a filter.
Re: DS18B20 Long Cables
Thanks for feedback.
In addition, in bsb_lan documentation, there is a chapter about DS18B20 with some advices (mainly adding 100nF and 10µF capacitor). To go further, they also refer to a tutorial from manufacturer for very long lines (>100m).
In addition, in bsb_lan documentation, there is a chapter about DS18B20 with some advices (mainly adding 100nF and 10µF capacitor). To go further, they also refer to a tutorial from manufacturer for very long lines (>100m).
Sébastien - espRFLinkMQTT gateway RFLink MQTT on esp
Re: DS18B20 Long Cables
hey guys
for me this 1kOhm pullup definitive work, I connected the ESP8266 today and it worked straight away!
I have an 10m line on the controller then a Stub of 2m with 1x sensor, then 20m line down in the ground.
@seb82
I also tested with a 100nf capacitor and a 100uf, but that didn't work for me.
for me this 1kOhm pullup definitive work, I connected the ESP8266 today and it worked straight away!
I have an 10m line on the controller then a Stub of 2m with 1x sensor, then 20m line down in the ground.
@seb82
I also tested with a 100nf capacitor and a 100uf, but that didn't work for me.
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