Thanks for the video. I ordered a capacitive sensor and will add it to my projects queue.

As expected, another superb exposition! Thank you Andreas.

I always had doubts on which one of these sensors to use. Thanks for explaining so well and solving my dilemma.

As we don't live on the surface of the sun the moisture does not need to be measured multiple times per second. Limiting measurements even to once every 5-10minutes increases the lifespan of the cheap sensor drastically as the lack of constant dc current means the copper corrodes much slower. Of course the time frame between measurements could be increased even more for a longer lifespan.

Great job, Andreas. I love the detail you've gone into, even finding the schematics for these unknown models.

Hi Andreas! You can not imagine how valuable this video is for me! I know programming but almost nothing about electronics. I have started about a month ago and your videos are helping me a lot (I still don't understand a lot but it's a way to know what to study). I will try to reproduce your sensor and connect it in an esp32! Again thanks a lot!

I know it's one of your old videos, but this is incredibly helpful. Thank you again Andreas!

Thanks Andreas! If I'm studying to develop a lora connected watering system for my plants is only because of you. Thank you for inspiring and explaining things in a way that is both fascinating and simple!

After a heck of a lot of failed tests, I went to an AC drive detection scheme initially seen from National Semiconductor in the later '70s. My version drives a Ti electrode at around 100khz and 12v peak to peak capacitor coupled (a 555) - neither value is too critical - and senses via a voltage doubler (or a few of them for water level in a tank) consisting of two diodes and two .1uf caps loaded by 100k and directly driving an arduino or ESP logic input for water level, or with different loading to suit your electrodes, an a/d converter. Water has a dielectric constant around 80 - so here we are using the capacity change as water is more or less present between the electrodes. I'm using titanium wire for those (pure) as in most cases it wouldn't corrode even electrolytically, and have had one system (for cistern water level) in continuous use for around 10 years now with no maintenance required. Nothing else ever survived even a whole year - floats stick, optics cloud up, any DC stuff corrodes and so on. Sadly, I didn't do a full documentation on this yet - it's so simple I just remember it, maybe I should and share it - or maybe Andreas can, he'd do a nicer job. Nice pics/plots of what I did do are here: www.coultersmithing.com/forums/viewtopic.php?f=59&t=904&p=5584&hilit=water+level#p5584

I didn’t know there was a non-rusting sensor solution. Thanks for sharing

the quality of your content is unmatched! a comprehensive walk through the circuit diagrams and a solution -- what more could you ask for

Totally unbiased analysis showing which of the sensors really work. Thanks for the improved content.

Nice video Andreas.

One more minute to see the finished protected sensor with the material you mentioned would have been a nice touch. Overall it was a very interesting and informative video. Thank you.

Thank You! I went through EXACTLY the same problem. There is an ON-OFF trick how to slow down the unavoidable corosion, but all attepmts will lead "everyone" to capacitive sensors. Thank You again and more, more, more videos.

This is just what i needed. Now i can start my garden without flying blind. Thank you Andreas!

Your Swiss Guy intro convinced me!! 😅😁😁😁 Great video!!

To extend the lifespan of the cheap sensors, you can use 2 analog pins one as a digital output to power the sensor and one as analog input, you take the reading and then turn off the output pin. On the next measurement you just swap the pins. This way you are simulating an AC behavior. The copper will eventually corrode for chemical reactions over time, but it will not be accelerated by flowing current.

Perfect timing... I couldn’t understand why my plants were being over watered. I’ve ordered the recommended sensor. Thanks again.

Thank you for taking the time and effort to make and publish this. I was looking for a soil moisture sensor and this was very helpful I'm the decision making process.

It is always a pleasure to learn something from you sir. Keep it up :)

Well explained. I have made various moisture sensors, including resistive sensors and capacitive sensors. Both have their pro' s and cons. You already mentioned most of the disadvantages of the resistive sensors. Those can be minimized by interrupting the power to the sensor and only switch it on for a few milisec when you measure and that can be done say 4-6 times/day. More than enough. I also do not use copper, but Iron. This way sensors last several seasons I found the capacitive sensors (made with 555 or HC14) a bit sensitive to surroundings, apparently their wires pick up stray capacitance. I was surprised about your sensor working with a plastic bag around it, it will, but probably not well with so much airspac around it. I tried with heat shrink.... that didnt really work. Lacquer and plastidip (expensive) do. One more thing about that various resistive models. If you use the analog output, the 'module' that comes with it is usually superfluous,as it connects directly to the sensor

Hello Andreas, this is an excellent video. I am Electronic Engineer but never had the opportunity to practice it. I love how you explain the principle with the electronic schema. This video has been very useful for me since I was doing the same type of research as you by comparing different probes. I am typing to make a wifi watering system (possibly solar) and this was very helpful. Now, I have heard that the consumption of this device was abnormally high and that better solutions should be found (unless you don't mind about consumption).

Great video! I've had this problem a few years ago with water level detectors. Even with small voltages the electrodes disappeared after a few days. I tried replacing them with stainless steel electrodes, it appeared it didn't corrode, at least not as fast, but I now realize it might create even more toxic waste as a result because of chromium. I wish I knew about the capacitive sensors back then.

capacitive sensing is a good idea. Also: Don't forget to protect the whole sensor, including the electronic components with lacquer, not only the sensing part.

of course i believe you master! and i proved it

This is brilliant... thanks! Love the circuits you separate to understand what it actually does! Kind regards from Croatia!

thank you Andreas. Yet another phenomenal video. I will be purchasing a few of those moisture sensors soon.

Electrolytic corrosion is the death of almost all electronics. That is the reason why it is important to block direct current. Those cheap moisture sensors are actually a nice learning tool and included in almost all arduino-kits. And the rapid electrolytic destruction is a feature, it shows beginners the importance to think about these problems and how to avoid them. :) The naive approach is, to add a resistor to make a voltage divider and put them between Vcc and GND and measure the voltage drop with the built-in ADC. This makes them corrode away in no time. The next less naive approach is to put the voltage divider between a port-pin and GND and enable them only a few times to measure the value. This slows it down but doesn't solve the problem. Third approach is, putting it between two port-pins and to take measurements they are driven with alternating current ( alternate between high and low on those two port-pins, always one pin high and the other low and taking measurements in between). This remove almost all direct current, but some direct current might be still present if the program takes longer when one specific pin is high (i.e. when taking a sample only in one code path). Then you can fix the program, maybe add a capacitor in series with the voltage divider and so on. Then you might introduce the capacitive sensor. It is a learning tool. :) And when all flowers are dried up, you can build electric neon flowers: ukposts.info/have/v-deo/qpKjnqGxhHuhsYk.html www.bigclive.com/nixie.htm (and they don't need water) Edit: The other thing I wanted to mention is: Conformal coating helps a lot and it is extremely easy to retrofit, just get a spray bottle of kontaktchemie plastik 70 (or similar product), clean the PCB, and spray it (be careful with connectors). Conformal coating could be done in the factory, it is very cheap but it isn't done to increase the chance for water damage. Water damage means no warranty and the customer has to buy a new product and that is what some vendors of some products want (Especially the vendor of particularly hard to repair laptops that get turned into a PC when a corroded trace or pad is replaced with a wire). The easy way to make your own, and more robust, moisture sensor is a screw terminal with two nails in it. I mean the screw terminals used to install light fixtures (They are called Lüsterklemme in German, this should give good results in google image search).

Great video! Ive learnt new things. Anyway, instead of using capacitive sensors, what about using graphite as sensor probes? Graphite are used in many electrolytic cells as electrodes so they won't corrode away like copper does. Plus, i think graphite can be cheap too as it can be found in pencils.

I used the striped sensor as christmas tree water sensor, it corroded in only 2 weeks totally. Thanks for the video, really concise and clear information here!

Thanks! That is informative. Bought some of the bad sensors, didn't thought about it, but it totally makes sense.

I laugh when you said "this is not a channel about good looks and makeup" at 8:42 . Brilliant and informative video as always Andreas!

Resistive measurement works perfectly fine. I use two Stainless steel rods that are sampled for 1ms every hour. Inbetween sampling there is no voltage. It is running for 5 years now without issue.

Thank you Andreas for those explanations !

I love all your videos. But especially the ESP & sensor ones 😁. Thx for all the effort you put in your videos.

You could also just switch the power to the sensor on for just a splitsecond fir a measurement

Just bury an ESP8266, the water will change the signal strength. 😎

Thank you for this informative video. I am happy that I have opted for the capacitive sensor on Ali. Now, I also understand why it works without corrosion :)

Just bought it for my pi pico garden project, thank you so much!

Just switch polarity every time you check moisture. Second thing - buy only gold plated sensors.

What about using AC to measure the moisture? I would expect that the simple sensors should life much longer. Also a pulsed current, only measuring the moisture a few milliseconds every hour or so should help. It is not neccessary to measure all the time. What do you think?

Nice work! I need to measure the moisture content of the floor material in my beehives, so this was useful.

Very interesting. I’m not that versed with hydration systems but work on a lot of automation systems dealing mostly with HVAC. I like your simplified explanation and appreciated field data. I am certain that this technology will become more apparent as people are continually looking to automate processes. Keep up the good work.

Hi, I really like your videos. But this time I am a little bit disappointed. I thought you will bring a "real" solution. I got the same problem like you and I found a way to solve the problem forever without any toxic stuff (plastics, softener, etc). And without having any materials that can corrode. I took two graphite electrodes, printed a holder for them and connected them to a controller of the cheap china sensor. To prevent any way of electrolysis it changes the polarity of the electrodes every 24h. I take data once every 10minutes. To get perfect values I did the following: I took 500g soil and put it in a compartment dryer about 48h around 60°C that it is 100% dry. In the next step I took 30g of the soil and put water in it. After it was saturated I took the values from the 100% wet and the 100% dry soil - each with 30g of soil. Then it was time to get some values between these measurements because it does not change linear. Here are my resultes (6cm dipped electrodes, 5mm diameter) : Moisture // Value 0% // 1024 20% // 634 40% // 339 60% // 321 80% // 307 100% // 260 It shows, that I need to repeat this measurement with moisture values between 0% and 50% in smaller intervals. But if we think about the resilience of nature it isn't so important. Anyway: Thank you for your great videos and explainations.

The green stuff should be copper oxide, which is classified as a hazard to the environment. Considering though, that there are a lot of copper pipes out there that also oxidize, I guess it's not all to bad. Fun fact: the statue of liberty is made of copper and oxidized over the years, that's what gives it its distinctive green color

Very valuable information through this very clear explained test ! A must know for everybody who wants to do this kind of moisture measurements ! Thankyou !

Dear Andreas, your study is priceless. Saved me tons of work and some money (and I'm afraid a friend of mine is not going to receive any payment of a device he was going to build me...) Thanks for this. A Venezuelan exiled in Lima, looking to come back soon to my country, once freed. Cheers!

the green stuff is probably mostly oxidized copper.

10:32 I love like he talks to us like we are computers, and he is the software running us. Finally someone who speaks my language 💜🤖

Dear sir, I exactly understood what you meant. No electrical current as it will do electrolysis function, within different metal, different electrolyte, or even different potential differences in a circuit. The capacitive way is I will always like. Thank you for this enlightment. Thought it was just that simple to measure soil moisture. Thanks again.

Very useful. I'm glad that I was lucky by purchasing the last model.

I though this was a channel about beauty and make-up

Yea, just pulse the sensor every couple seconds

Thanks for the analysis. I am about to install moisture sensor in my home garden (30-40 of them) and waned to understand the difference between all types of moisture sensors available in the market before i place the bulk order. This 10 min video saved me from going through all of their datasheets. One info missing from this video is the resolution of these sensors.

An informative video that points out the short comings of the different types of commercial sensors that can be purchased. It would of course be easy enough to elongate the life of these but because they rely on conductivity, they do need to be exposed to the soil, whereas a capacitive sensor, does not so can be coated to protect it. 2 nails would suffice to replace the copper electrodes if you wanted longevity, or because of the price of these types you could just replace them every year. Thanks for the video, it gives people insight into the different types to use

Straight to the point. Thank you for protecting us customers against this cheap China sensors! Thumbs up!

Du darfst kein grünes Uranglas für Deine Experimente verwenden, dann löst sich auch das Kupfer nicht ab .. ;o)

Great video. I'm doing a lot with this sensors. At first i was using the crappy cheap ones. Now i replaced them all with the capacitive sensors.

thanks for all the videos, another great one, I will support you soon

What if you use the first type but switch the polarity regularly?

If I try one of these I am just going to buy a couple stainless bolts and connect them to the sensor. Pot the rest. Bam

Hello,very good explication about the sensor(most of the channels that made a video about the moisture sensors didn't said anything about the dangers of the cheap ones) but can we can we solder a the cooper exposed terminals with a layer of solder?What do you think?

Really Cool Andreas. I'm using those sensors in a project with attiny85 and sending the info via RF433Mhz to a arduino nano connected to a raspberry pi. Those sensors have a short lifespan indeed, but i think that humidity doesn't change that often or that quickly, we don't need to be always reading, nor always powering that sensor. So i have used powergating and the sensors last way longer now! :) I have one Capacitive soil sensor, but i still need to test this. All the best!

I always enjoy you videos but this one was VERY useful! Thanks!

I did something like this a while ago. I only measured every 15 minutes, using the AC measuring method with an arduino. The sensor itself was very reliable and basic, just two stainless steel rods stuck into a pair of screwable wire connectors. The system was running for a year with no loss of accuracy and absolutely no damage to the rods. The rods were 4mm diameter and 10cm in length.

The "chemistry" that happens when one leg of your humidity sensor dissolves, is the oxidation of your anode. To prevent this, you can combine the following two strategies: (1) use metals that form a stable anode (gold, platinum, titanium, nickel, carbon) which means that when using PCB technology, your limited to ENIG and more advanced plating technologies, and (2) apply as little as possible voltage between the legs of the sensor, which means use as little current as possible to measure the resistance and amplify the voltage with e.g. an instrumentation amplifier. I agree that the capacitive sensor is a much more elegant and robust approach though! The working principle reminds me of the good old Theremin :)

Great , informative video. 👏👏 Good presentation with explanations.👌 Conductive metallic probes can get corroded over time because of pH value of water, as also other chemicals. Wonder why non-corrosive probes such as stainless steel were not used.

Thanks for the video. I was just working on some prototype using the capacitve sensor you mentioned here as this video came in. What would be nice perhaps is to do a follow up video on how to use the sensor in combination with a battery powered ESP8266 using deep sleep (max interval perhaps). I have it running in combination with deep sleep but still the battery (LiFePo 3v, 1200mAh) lasted only two days. Then I realized that during deep sleep I left the sensor powered to 3v so perhaps that drained the battery. I guess I should control the power of the sensor from the ESP either using a transistor or perhaps directly from the GPIO. So, indeed maybe an good idea for a next video project now that you discussed the various sensors? Cheers, and thanks for all the great videos. Love them (even with the funny accent)!

An entertaining and informative video. Thank you Andreas.

Thank you, I got them and I am experimenting with them and espeasy . So thank you.

Andreas - love the channel. Extremely informative and I have tried many of your projects. Along the same lines as moisture sensors, can you explain why ph soil sensors work so poorly as well? Maybe there is a best configuration for probes (single vs double vs glass)? It just seems that given the correct conditions, soil ph should be able to be measured with metal probes without having to put the sensor in a separate solution. Any help, advice, or guidance would be greatly appreciated! Keep up the great work!

Nice video - came across your channel and this vid as I'm contemplating seeing if I can use a capacitance sensor with an arduino or ESP32 and LoRa to monitor the beds on my allotment (2.5km away) so I know which beds need watering and when , so that I can maximise the use of my time down there. Looks like your channel has all the info I need to start off my very first project - thanks.

Thank you for this I need to automate my watering system in South Australia (driest state, driest continent) and this has saved me a lot of time esp as the soil is also very alkaline and salty clay. I'll let you know how I go.

Thanks for sharing 😀👍 Interesting project 👍

Awesome video! I was about to order some cheap moisture sensors from Banggood, when I suddenly though to myself "Hmm, some weeks ago there was a video I wanted to watch about these... Time to watch it before ordering!" So you actually saved me a few bucks and some headache, thanks! :)

Useful and interesting. Great video. I like these kinds of videos a lot. One just need to watch a single video and everything is said.

Amazing video as always Andreas.

Muchas gracias profe, muy educativo e interesante el video, para este tipo de sensores tan útiles. El sensor de patas delgadas y macizas es útil para una ecualización del riego en la fase de diseño, por su características físicas, permiten una fácil penetración a la tierra, pero no dejarlo expuesto por periodos prolongados, debido a lo que usted expone en el video, y el sensor recubierto si sera útil para dejarlo en la tierra, claro incluyendo la mejora que usted menciona, recubriendo el borde, para así garantizar un riego proporcional a la humedad del suelo en todo momento. Saludos.

Thanks, Andreas, Excellent like always.

I just bought 3 of these on Aliexpress, then I found this video... Gotta love Andreas :D

Thanks for the Video, Andreas. In a proper industrial solution the driver for the sensor is always alternating current. This prevents unwanted electrolysis even if the sensor is capacitive and the isolation gets damaged. With leakage detection and indication you know there is a fault, distorting your measurement. A possible easy solution can be to couple a PWM signal out with a capacitor and feed back the sensor over an rectifier + capacitor/lowpass. Sounds complicated but are less components than a NE555 based oscillator and most of the components are used in the DC application anyway + Micro-controllers love to PWM. At all you have to think about if a capacitance touch-less measuring method is the best for you: You get a phone call and your plant gets water ... this can happen;) Using the direct contact method with AC coupling is the stable (homebrew) method i think. In addition what Eman Retzun(Nutzer Name?) said: there shouldn't be any component in the sensor path, including the amplifier if one is needed, that draws more current than an Arduino can switch, and on/off times for plant moisture measurements can be very sporadic. Where's my copper gone?!?: From the one electrode to the other, negative electrode:) ... but other stuff can get in solution that was bound with or was under the copper. So don't use permanent electrolysis on your potatoes. What happens in a fault situation?: Your house gets messy and the expenses are far more than a 3$ sensor. Ever thought about the magic of the capillary effect? -> You build a closed system, where only so much water physically can get in what's needed. High-End space material like terracotta does the rest. If you can't withstand, than you can put a moisture sensor outside of that all as secondary safety measure. And this one can always be dry, yelling an loud alarm if it gets wet:)

All the sensors I use for soil profile moisture sensing rely on frequency or time domain reflectometry. They last forever. However, I know there are also capacitive sensors on the market suitable for science or agricultural use...now I know how they work. Thanks very much.

did not really ever thought about getting a moisture sensor... But after watching this advise I got an capacitive one :D

I have here a few self destructing moisture sensors, never put them to use because of that. Now I shall buy the capacitive version and forget about the other one! Thanks mate!

Good video for anyone planning to use moisture sensors! Btw,with reactive components the correct terminology is 'impedance' not 'resistance'.

nice video. always wondered how these sensors worked.

Great video. Thanks for explaining

Good video. Been too busy lately. At least I found time to catch this one.

I know this has been awhile. But I came up with a probe that works really well, is super cheap, and easy to make. I simple put three long pieces of coax cable snugly into a 1/2" pvc pipe. The probe is sealed with simple pipe caps. I found that putting a bolt through the bottom for grounding made it more stable. All this stuff is super cheap and easy to work with.

Very useful information, thanks for sharing with us.

Very interesting!!! Thank you for that information! 👍👍👍

I have the same experiences with both sensor types. The capacitive sensor, however, still has a problem. If the soil changes from wet to dry, a permanent gap in the soil can develop there, which makes further measurements useless. Of course, it depends heavily on the soil conditions. Maybe high-frequency radio waves are the solution. I did a first experiment with a Bluetooth tracker and measured the dBm. Looks promising. I have packed it waterproof and buried about 15cm in dry soil. Then I irrigated the soil bit by bit and found noticeable changes in the dBm.

Hi Andreas, great video! Is there any way to share the schematics of your sensor?

thanks a lot for your tests, very useful.

I didn't realize there were generics of the capacitive sensors now! From what I've heard they are a lot more accurate than the resistive ones. Just so you know though, you can prevent the destruction of the resistive sensors by only applying power only for a few milliseconds at a time whenever you need to take a measurement. I used to just connect the +5v pin to an output pin on my MCU and turn that output on when I need to take a reading.

Hi, Your explanation is very good. Please clarify the Range and Accuracy of Capacitive Moisture sensor.

You can solder some stiff copper wire onto the legs of the cheap sensors so the PCB tracks are not in the damp soil, but this is only a partial fix. I noticed that when the temperature drops at night the conductivity of the soil changes and of course this makes it difficult to set accurate limits. Another problem is that when you add liquid fertilizer like "Miracle Gro" the conductivity of the soil increases as does the chemical reaction on the wires. Basically then Andreas' suggestion with the capacitive sensors and waterproof dip is the only reliable way to go.

Thank you Andreas!

Hi Andreas, thank you for the video, very informative, do you think the plastidip would take away from the sensitivity much? what if the capacitance sensor was coated in several coats? would it loose it's ability to sense through the porous rubber like coating?