Working with a capacitive soil moisture sensor

[@karzokalori697]

Thank you for a great and straightforward video mate! I would love to see more content about this!

[@TasteTheCode]

Thanks. I do have one other video about creating a sensor connected with ESPHome and Google Assistant.

[@AgentX02008]

I have created a similar device for a Senior Design project for wireless soil moisture sensing based on this device. This is a pretty good summary of how it works from what I have found/experimented and I wish it'd had been up prior to my research haha.

[@TasteTheCode]

Thanks for the good words. It didn't help you soon enough but I sure hope it will help someone else.

[@cromossomos4861]

Nice video, but i have a little concern about this device : According NE555 datasheet the min. VCC is around 4.5V and the 662K regulator will provide just 3.3V. I dont know if was a manufacturer error, but this kind of issue can cause unprecise reading or malfunction. Bypassing the 662K and working with 5V can be more safe.

[@TasteTheCode]

The input can be 3.3 or 5V but the output is always capped at 3.3 so it is compatible with multiple microcontrollers.

[@AGG69]

They are using NE555 marked with 20M, which is proved to work outside of manufacture spec of 4.5V down to 3.3V. So, it is well working with a power supply 3.3 - 5V. Personally tested, and there is no difference with the models using TLC555C or TLC555I able to work from 2-3V.

[@manukalias]

Thanks for very clear informative Video about this Capacitive Sensor. 👍👍👍👍 Were you able to make any use of it in real garden situation 🙄🙄 I am going to order these sensors later today and try experimenting.

[@TasteTheCode]

Unfortunately not yet. As you might already know, life gets into way when planning 😅😅😅 Hopefully, I shoud get to it soon. However, the sensors are great, so go ahead and start experimenting.

[@dshshajskj6143]

will the salts present in soil effect the sensor value? or fertilizers

[@caffeinatedinsanity2324]

For this particular sensor, yeah unfortunately. I got a sensor that uses TDR but I bought it for like 30$ CAD (while this sensor costs at most 5-6$ per unit). I read some litterature once that high frequency signals sent through soils will reduce the effects of ions on the dielectric or capacitance readings.

[@funone8716]

Could this sensor be modified to sense moisture percentages of air in a compressed air (up to 150 PSI) application?

[@TasteTheCode]

It shouldn't be affected by the pressure but since it will be air, I don't think that you will get precise readings as I had to dip it into water so I can move through it's range. I think you are better off with something like the DHT11 or DHT22 but I don't know if they will be affected by the pressure.

[@caffeinatedinsanity2324]

Honestly, I saw the schematics once for this sensor and I do not trust converting its output signal linearly into volumetric soil moisture content. According to some literature I read, the best way would be to get a dielectric constant reading, to then convert with something called Topp's equation. And I am not sure how one could translate this sensor's output into a dielectric constant value, or even just capacitance, from which you would calibrate in mediums with know constants.

[@TasteTheCode]

Does it need to be that precise? What I need to know from it is if there is moisture or not so that I can turn on the watering. There is no value in knowing the difference between 20 or 30%.

[@bobalainen3]

Nice video, but hardy speaking, ADC and moisture relation is not linear in range 0-100%. I am trying to do similar soil moisture tester with UnoR3 and mega2560.

[@TasteTheCode]

Thanks for sharing. I know that the relationship is not 100% accurate but in general the relationship between wet and dry is and the output is usable triggering and alarming in a monitoring system.

[@bobalainen3]

@@TasteTheCode now i use 9 sensors on the mega2560. i use 9 buckets with soil. for stable adc results i use analogread command and 500 ms delay after . for measuring i use only the third analogread result. delay less 200 mn is not good because ADC needs time to discharge the capacitors. average of 10 readings shows nice stable value . at least variation is within 5 percentage. now i try to find calibration curve volumetric moisture vs ADC values on sandy loam soil. looking for you new video and progress.

[@TasteTheCode]

@@bobalainen3 sounds awesome. I would love to see your setup if you have it somewhere on the net.

[@bobalainen3]

@@TasteTheCode i send the link by FB messenger

[@dshshajskj6143]

will the salts and fertilizers in soil effect its readings

[@TasteTheCode]

Possibly yes. I know that salts do corrode the other types of sensors. You may need to experiment a bit in order to find the right values but it will definitely make a clear distinction between wet and dry.

[@dshshajskj6143]

@@TasteTheCode is there anyother way to measure moisture of soil nullifying the effect of salts and fertiliers based on current conduction possibly?\

[@TasteTheCode]

Not that I'm aware of. If you have a soil sample without any fertilizer, you can maybe measure that and somehow offset the reading later bit it won't be simple.

[@caffeinatedinsanity2324]

Ideally you'd want a high frequency capacitive or TDR sensor, but those are not cheap.

[@markocenicola]

why do all my sensors write 755 instead of 530?

[@TasteTheCode]

The calibration is different on all. Do they respond to changes in humidity? If they do, then you can map your output based on that.

[@markocenicola]

@@TasteTheCode yes they respond, thanks so much, I have another question, why the value changes in order of the deep of the sensor in water?

[@TasteTheCode]

Put it simply,it changes the capacitance of the surrounding. This is how they work and are able to detect the change in soil moisture, the more water there is, the higher the output.

[@markocenicola]

@@TasteTheCode Thanks for the help!

[@ajinkyatamhane985]

How to to attach different probes to this sensor

[@TasteTheCode]

I don't understand your question. What do you mean by different probes?

[@ajinkyatamhane985]

@@TasteTheCode for example if I want to measure moisture at more deeper level.....then...can I extend the probe...by soldering wire to the existing structure

[@TasteTheCode]

@@ajinkyatamhane985 I'm not sure that you can do that with this sensor because the value is dependent on the capacitive coupling on the PCB. Adding external probes will change that capacitance and the value will be wrong. You can bury the entire probe inside a watertight enclosure and extend the communication wires from the top.

[@ajinkyatamhane985]

@@TasteTheCode really thanks for detailed reply

[@TasteTheCode]

You are welcome!