DFROBOT Gravity: Analog Capacitive Soil Moisture Sensor- Corrosion Resistant

This capacitive soil moisture sensor does not corrode like the cheapy little non-capacitive/standard soil sensors you see around (those usually corrode within a month or so, sometimes less). This analog sensor from DFRobot is supposed to last years without going bad!This operates at nearly the same voltage (3.3 ~ 5.5 VDC) and works without additional resistors needed. The moisture range differs from standard sensors. Dry is 520-430, moist is 430-350, and wet is 350-260.On this sensor, you will see a white line near the component side - this is your moisture/water warning level, meaning you do not want moisture above that as it can damage the components. I am using this in a planter that will be watered on and off as needed and didn't want to worry about components getting wet, so I put it in a project box (uxcell Waterproof Plastic Electric Project Case Junction Box (2.3x1.4-Inches, 5pcs) that I then cut a hole into on the side with a dremel tool about the width of the sensor. I also cut a smaller hole on top for the sensor wires. I slide it in and added some foam padding to keep it in place. Lastly, I used acid-free silicone (GC Electronic Grade Silicone Sealant / Adhesive (3oz.) : 19-155) to waterproof the ends.Attached are some pictures to help give you an idea of my process water proofing it. I didn't take one with silicone on it yet, but that is a crucial step!I love this thing. I'm so happy with it and excited to be using it in my smart greenhouse project. I will keep this review updated in case it fails early or I run into trouble, but I certainly feel MUCH better about using a capacitive moisture sensor from DFRobot than the cheapy standard ones that corrode after a short time... who wants to keep replacing those? Not me.I highly recommend you do a search on the web for "dfrobot capacitive soil moisture sensor wiki" as they have a lot of great info on this device, including example code and recommendations, best practices, etc.I hope this review was helpful and will save people some time!

It's a good little moisture sensor for an Arduino or any other microcontroller out there. Very sensitive in terms of reading an moisture. However, and oddly enough, the drier the moisture sensor, the higher output voltage occurs. In other words, when you dunk this in water, you're output voltage would be a lot lower than than when it's completely dry. I thought about the behavior of why this happens and I only thought about a simple reason why: Kind of like a touch screen a cell phone, when it comes into contact with other elements, the capacitance discharges. The moisture content and output voltage are INVERSELY related.One very large downside to this product is that the circuit at the very top is exposed. You can see the exposure on the metal pins on the 555 Timer and the capacitors, which is not really okay. However, you can probably resolve this if you put some silicone glue on it. One thing I do like about this product is that it lasts longer than your little tiny copper resistor rated moisture sensor.UPDATE: I finished my senior engineering project with this guy and it got the job done. During my project, I had to come up with some way to characterize the sensor since there was no information about its characteristics. The graph below will kind of show you the consistency of the moisture sensors. The different colored lines represent each moisture sensor used since I used five for my project. The dotted line represents the "trend line". I recommend experimenting multiple sensors for yourself. You can use this data to determine when particular things occur for your program on the Arduino.

Stuck the sensor in flower pot, poured 2 deciliter of water around the sensor and got reading of 511. Now, about 1 hour later, I get reading 705 and increase stopped. Is that normal? Could it be that the sun warming the pot, the sensor and the electronics could have done it?

I bought one of these sensors. It worked as intended at first. But after about a week it just stopped producing any meaningful readings. The readings just are random. I checked the board with a meter and there is correct stable voltage. My guess is that they use cheap unreliable 555 timer chips which are faulty. The quality is extremely poor considering the price.

I like the concept, but these do not seem to work. I purchased two of them, and tried both with an ESP32 Dev board and an Arduino Uno R3. I was able to verify with a multi-meter that the voltage changes when it goes from dry to wet and back, but the ESP32 always reports the value as "4095" and the Arduino value fluctuates from 917 to 920, no matter if it's dry, or in an inch and a half of water. I suspect the voltage is rapidly oscillating, and preventing the ADCs from getting a good value, but I don't have a scope to verify that theory. I'm surprised anyone has gotten them to work, since both of mine behave the exact same way.

Works well for my gardening project, calibrated in air and water. Had to use electronics epoxy for the electronics area, but it doesn't corrode like the bimetal types that are significantly cheaper. But you get what you pay for sometimes.

I've been using this as a part of the beginnings of automated watering for my cacti and succulents. Using an tiny board I was able to mount to the upper rear portion of this sensor, I was able to display soil moisture as a color between Red and Green. So far I have had no corrosion issues.