ESP32 and multiple Capacitive Soil Moisture Sensors

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ciscomike
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ESP32 and multiple Capacitive Soil Moisture Sensors

#1 Post by ciscomike » 29 Apr 2021, 21:38

Hi everyone,

I am using an ESP Wroom 32 dev board, flashed with the latest ESPEasy release.
I am trying to add 5-6 Capacitive Soil Moisture Sensors on different analog pins of this board but I'm getting results from only one pin (36).
What I am doing wrong?

Thank you in advance,

Mike

TD-er
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Re: ESP32 and multiple Capacitive Soil Moisture Sensors

#2 Post by TD-er » 30 Apr 2021, 00:04

For the ESP32 you really have to make sure which ADC the pin is connected to.
A number of pins is connected to ADC1 and others to ADC2.
See also the documentation: https://espeasy.readthedocs.io/en/lates ... ty-and-adc

Pins connected to ADC2 will not work when you also use WiFi, since that ADC is also used by the WiFi circuit, which has higher priority.

ciscomike
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Re: ESP32 and multiple Capacitive Soil Moisture Sensors

#3 Post by ciscomike » 30 Apr 2021, 10:37

Thank you for your reply,
Even using the ch1 pins doesn't give me any measurements, only if I use ch1 pin 36.
I know that using ch2 pins might be unstable due to wifi bus.
Any ideas why rest of ch1 analog pins wont work with any analog input?

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Re: ESP32 and multiple Capacitive Soil Moisture Sensors

#4 Post by TD-er » 30 Apr 2021, 12:38

What voltage do you apply to the pins?
And just to be sure.. this voltage is relative to the GND of the ESP, right?
You don't have 'calibration' enabled I assume, so you should get values between 0...4095

See also: https://randomnerdtutorials.com/esp32-a ... duino-ide/

easy-mrmomba
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Re: ESP32 and multiple Capacitive Soil Moisture Sensors

#5 Post by easy-mrmomba » 17 Jun 2021, 17:39

Hey,

please check with a Multimeter the Voltage on the Capa-Sensors.
Don't! Using the 5V Output pin
The Current is to weak / low.
Capacitive-Sensors are the same as an condensator. And the sensors have to "charge".
If you try this with the output-pin, you may have not enough Power to load them and your measurments are .... wrong.

=> Information:
If you try to communicate over a "long distanze" you may have to use a line-driver. because cables work as an condensator too - and the internal "driver" is to weak for a clear High-Low-Signal.

Next steps:
---
Measure supply Voltage - near the sensors
Measure the Voltage after the sensor / signal line
---
Drive the sensors directly without the output-pin from ESP

Haldi_2
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Re: ESP32 and multiple Capacitive Soil Moisture Sensors

#6 Post by Haldi_2 » 31 Jul 2021, 14:23

i'd really recoomend using an external ADS1115 ADC.
The internal one will give streched values when battery voltage drops to 3.5V and lower!

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