Can I run multiple Analog capacitive moisture sensors per nano

  • Excited to have my square foot garden watering automation almost worked out on paper. I am curious if there is a way to run multiple (3-4) capactive moisture sensors per arduino nano? I will be using HA to control the watering, based on moisture levels of all sensors. If this cannot be done, what sensors should I use that will not degrade?

  • Mod

    @mrhutchinsonmn what interface does the capacitive sensor have? (How is it connected to the Arduino; what signals does it use?)

  • The capacitive sensor I have has VCC, Gnd, AOut... I am glad to use something else if I can run multiples on one nano

  • Mod

    @mrhutchinsonmn most Arduino Pro Mini have 6 analog inputs, so you can connect 6 sensors. Most Arduino Nano have 8 analog inputs. If you want more you can use a multiplexer or external adc. Depending on your needs, using multiple Arduinos (with 6-8 sensors each) might make more sense than adding external hardware. Or use an Arduino Mega; it has 16 analog inputs.

  • @mrhutchinsonmn Thank you. Do you think 25' leads to the sensor will skew the readings?

  • Mod

    @mrhutchinsonmn I have no idea how the capacitve sensor's signalling works. Easiest way to find out is probably to measure with short and long leads and see what the difference is.

  • @mrhutchinsonmn I think 25' will affect the signal (which is analogue). But, if you calibrate the system with the long cable in place then you should be able to compensate for that. Is it impossible to put a radio module closer to the sensors?
    Failing that an arduino could measure the values and then use serial to send down a longer wire? You might even go as far as adding RS-232/485 if it is in an electrical noisy environment.
    I just got 12 sensors in the post yesterday, so I too will be experimenting with them in the greenhouse soon.

  • I am not sure if this is feasible to have 25' cables... Each needs 3 wires to connect.
    I am running the capacitive soil sensors in single mode with 3.3V ProMini on Battery. I do not see issues having 2-3 sensors per Arduino but more seems to be a wiring nightmare all over the garden.

  • Thanks for the replies. I think I will just go with 3 sensors per raised bed, per nano. That will keep the runs under 10'

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