I need help to understand a basic soil moisture sensor circuit

Hi, I want to connect and use two sensors to MCU (nucleo64). But before that, i should understand these 2 circuits.

1- Where do we see measurement of the SOIL PROBES on Nucleo64? (It is connected to VCC not MCU.)

2- What is the purpose of the resistor on the below? Why we don't connect the HUMIDITY PROBE to the MCU (nucleo64) directly?

Here is circuit: https://i.stack.imgur.com/73wNS.png

by hernancrespo89
September 20, 2019
  1. SOIL PROBES needs power, so connected to VCC.
  2. resistor is used to pull signal from sensor down, so MCU can read correctly.
by wangwg88
September 20, 2019

Thanks. I have also two other questions.

1- Shouldn't it be two probes are there? (if i'm not wrong, there are two probes in soil moisture sensor. but it says SOİL PROBES (2) and HUMIDITY PROBE(1))

2- whatis the purpose of 1k resistor? why we don't connect VCC to PROBE dircetly?

by hernancrespo89
September 21, 2019

The 1k resistor is probably to limit the current to something reasonable if the probes are shorted to-gether

by Foxx
October 05, 2019
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