I am making a Soil Analysis system with an Arduino Uno, but I have run into a problem and was wondering if /r/learnprogramming could help!

The moisture sensor section of my code will not output the data to the Serial Monitor in Arduino 1.7.1 IDE. I am not sure why it's not working. Running the moisture sensor code by itself works, and I just copied and pasted that code into my combined code file since I'll I am running 4 sensors at once with my Arduino Uno.

These are the four values I need to output data on one baud rate:

  • pH value
  • EC
  • DHT temperature reading
  • Moisture Sensor Value
    I am currently missing Moisture Sensor Value when I run Combined1.ino

Here is the Combined1.ino code of the code from four sensors together that's uploaded to the Arduino: Combined Code Link
Moisture Sensor Link

Any help would be much appreciated!

  • /r/learnprogramming? Are we Reddit now?
    – Majenko
    May 23, 2016 at 22:44

1 Answer 1


Your second print section will always fail.

You have:

if(millis() - printTime > printInterval)   //Every 800 milliseconds, print a numerical, convert the state of the LED indicator

However, a bit before then you have:


So millis() - printTime can never be greater than printInterval since you have just set printTime to millis(). So millis() - printTime will always be somewhere between 0 and printInterval - 1.

Consider combining your different printing routines into one single printing routine so you are comparing (and changing) the printTime only once.

  • I got it to work. There is something happening with the DHT22 section that when the DHT22 is not connected, it fails and ends the loop. I just moved my moisture sensor code above that and it is now working. I will see if I can clean it up using this advice.
    – Phil Engel
    May 25, 2016 at 2:07

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