Comments: Soil Moisture Sensor Hookup Guide


Comments 21 comments

  • Hi. Why does this tutorial recommend "powering the ... Moisture Sensor ... between 3.3V - 5V", but then the battery recommended is 9V. Is that going to be ok? If so, why?

  • Why is there a breadboard? I appear to successfully get readings using just the red USB cord, the arduino redboard, the 3 wires (red, yellow, black) and the soil moisture sensor. Am I missing something important by not using the breadboard?

  • hi i'm looking at the photo:

    with the red, yellow and black wire going into the sensor - but they don't stick in there (they do stick into the breadboard) - does that mean i need to melt the tips of the red,yellow,black wires to stay into the moisture sensor holes?

    • oh, i get it. i needed to buy an extremely small screw driver and pinch the tip of the wire inside the sensor by tightening the screw.

  • How best to locate these sensors 15 to 20 feet away from the Arduino? One of your pictures shows 3-strand twisted wire, which looks like a great solution - but I can't find it for sale on Sparkfun. Thanks!

  • When using digital out to power the sensor with an Arduino, do you need some amount of delay from setting the digital out high before you read the analog in?

  • Nicely done but unless I missed something what about just using a small solenoid valve? Example: Adafruit Plastic Water Solenoid Valve - 12V - 1/2" Nominal PRODUCT ID: 997 $6.95 The creativity is great but it seems like once the cost of all of the mechanical parts are added up and given that none of the motors and parts were designed to be around water the approach seems questionable as a long term solution. Think corrosion and mineral deposits and short circuits.

    Not trying to rain on your parade because I think creative solutions are cool but I had to ask.

  • Hi! I have two students working on this project and they love it. They are having trouble with the lcd connection and unfortunately, my knowledge base does not allow me to help, I'm learning along with them. Any chance you have a schematic or photo of the breadboard setup with just the moisture sensor and lcd screen? They are leaving out the pump for now.

  • Hello. I am a Year 10 student working on this for a project but I am having troubles setting up a watering system. I've read the guide and comments below but I still don't quite understand the watering setup. Also, I do not have access to all the part you mentioned in the guide for the watering part, just some simple gears and motor. My idea was to have a plastic tube come down from a container of water and rest against a gear which is connected to the motor. The gear has holes so that when it turns and the plastic tube goes over the holes, the water in the plastic tube is let through. When the plastic tube is not over any holes, the water is blocked. My problem is how do I set it up so that the tube is firmly pressed against the gear so that water won't leak but still be able allow the gear to turn. Also, recommendations of other ways to set up the water system would be great! Thank you for reading!

  • Hey! I just started experimenting with the soil moisture sensor, but am having some problems with the readings. Basically if I stick it into water it generates a reading of about 580, and if I take it out the reading is about 280. After sticking it into very dry soil I still get a bouncy reading between 520 and 560. Are these reading accurate? Is there maybe some documentations that I could look at? I read through all of the links provided, but cant seem to find a more accurate guide on this...

    Also, do you recommend using any resistors? I saw in the schematics that a 10k resistor can be used...any suggestions on that?


    I also used this to check voltage readings: float getVoltage(int pin) { return (analogRead(pin) * 0.004882814); }

    Voltage is always around 3.8....

    Thanks and have a great day! Urban

    • Hi, those readings don't sound correct. The sensor should be reading close to zero when completely dry and close to the maximum value of your ADC (ie 1023 for a 10-bit resolution) when submersed in water. Are you powering the sensor with 5V? Why are you multiplying the reading by the decimal value above?

  • Could you please explain how this motor watering pump / thingy is supposed to work? All I can see is two photos, a parts list and some code, but no assembly instructions, no diagram, movie, text or anything that describes the working principle.

    • Of course! The way I set it up was with a bucket above connected to a crazy straw, that was secured to a laser cut piece (with water tight glue). This piece had a hole where the straw was and fit inside the gear that the motor was rotating, The hole was small enough that a drop would be let out when the holes from the gear came around, making a make sift watering system. The lasers cut piece was secured with an o ring to keep everything water tight. Hope that helps. It was a quick project, and there are better solutions out there.

  • What values are the resistors on this sensor ( I assume they form a voltage divider)? Other than the resistors, the two leads are pretty much it?

  • Good tutorial. How can I make the data to be sent to a screen that is not wired to the microcontroller hosting the sensor? Thanks, Luis G

    • You could do this with some Bluetooth boards, sending data wirelessly that way, we have a great tutorial to get you started with that Here. You could also use Wifi, and Here is a good tutorial on getting started with that. There are also lots of other ways that you could get creative, so I would look into wireless technology it's all pretty cool! I hope that answers you question and helps you a little!

  • What type/chemistry/brand of conformal coating did you guys use, if you don't mind sharing?

    • We bought a bottle of this for around the office, and have been using it on everything we can since.

    • Thanks, Joel! That's pretty much what I figured, and having ordered it I'm looking forward to protecting my circuits in harsher-than-benchtop environments in the future!

  • To make it a little easier to connect, you could also use the JST to Breadboard Jumper (3-pin) with the 3 pin JST connector with the soil moisture sensor and serial enabled LCD.

If you've found a bug or have other constructive feedback for our tutorial authors, please send us your feedback!