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Capacitive Soil Moisture Sensor

Ron 14 Mar 2021, 22:49 last edited by

Hi everyone,

I am happy to share my very first PCB design project with you. It is a capacitive soil moisture sensor using an ATmega328P and NRF24L01+.
The capacitance is measured as commonly done through a low pass filter using the ATmega PWM instead of a NE555.

I am not a professional in the area of microelectronics and pcb design and have thought me most of the things myself. This is also why I already have a ton of ideas for future improvements on the design with the switch to a NRF52 being on top. Still I am quite satisfied with my results so far. The pcb is tested and working (despite the fact that I soldered a wrong value capacitor and forgot the capacitor for the ftdi connector, which is already fixed). You can see example measurements on a plot below.
I have made all source files available on the corresponding GitHub repository.

I am happy to hear your thoughts and maybe some tips and remarks.

Cheers!
Ron
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Announcements • 23 Mar 2014, 08:24 • hek 2 Apr 2014, 14:39

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@NotYetRated Hope you'll find good uses and a fun time while building your sensors.
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My Project • 25 Jan 2024, 01:03 • OldSurferDude 12 Aug 2024, 06:03

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@OldSurferDude yes, you are correct. this sensor is capable of 50A continuous, which safely I would make it working at 40A max., but for such an important load as in your case I would go for a beefier one, like the ACS75x, 77x, but at this point I would also change the node's form factor for space and insulation reasons. On my application on the RV I have a max. curr. of 13A running on a AWG14-16 cable (European rules for RVs), so I did not ask myself too many questions beside, of course, safety. About the signal, it will be a sinusoidal signal swinging around Vcc/2. Vcc can be easily measured internally on the ATmega328. On all my DC sensors I measure Vcc at every loop, just before measuring the ADCs. Honestly, when the space is not an issue like in my RV, I would rather use a ring core current transformer, and I would get rid of noise, response time, power dissipation, but over all no need to cut any cable. Long story short, it has been a nice experiment and I used it for 6 months, and then I switched back to my RF-NANO based RS485-Modbus - Mysensors bridge connected to an off-the shelf power analyzer. Just for fun I attach a pic of my 12Vdc sensors installed on my RV. Forgive me for the spaghetti wiring on the right side, but this is an area that needs improvement.
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My Project • 25 days ago • Paul Scarbro 22 days ago

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@Paul-Scarbro There are multitude of solution, but since we are in MySensors Land, let's do a MySensors solution. You'll quickly see that doing that adds a lot of overhead. We'll use an Arduino Nano or RF Nano if you're going to go whole hog. It can be run from 3.3V or 5V DC, not AC. The reed switch would be connected to an input of the Nano and one of the outputs would drive a relay. The relay would drive the chime. Your C++ program would be something like: #define inputButton 2; // connect reed switch here #define outputRelay 4; // connect relay to this pin see MySensors Relay example #define RELAY_ON 1 // GPIO value to write to turn on attached relay #define RELAY_OFF 0 // GPIO value to write to turn off attached relay void setup() { pinmode(inputButton,INPUT); pinmode(outputRelay,OUTPUT); // put your setup code here, to run once: } void loop() { // put your main code here, to run repeatedly: if (digitalRead(inputButton) == 0) { digitalWrite(outputRelay,RELAY_ON); wait(2000); // wait 2 seconds digitalWrite(outputRelay,RELAY_OFF); // now wait for door to close while(digitalRead(inputButton) == 0) ; //does nothing until reed switch opens } } There are some subtleties that I may have glossed over, but this is the gist. By looking at the MySensors Relay example, you'll see how to integrate this into a MySensors environment. That's where you'd want to get the RF Nano. I've made the assumption you're familiar with the Arduino IDE and you've looked into the MySensors environment.
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My Project • 24 Aug 2016, 01:56 • Matt 23 Jan 2025, 16:25

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23 Jan 2025, 16:25

Hallo! Ich habe gerade meinen Aduino Nano mit einem GY-BME/P-280 verbunden über SPI verbunden. Im Sketch habe ich nur die PINS geändert und zwar auf: #define BMP_SCK 13 #define BMP_MISO 12 #define BMP_MOSI 11 #define BMP_CS 10 Ich bekomme aber bei der Ausgabe am seriellen Monitor nur "Hyroglyphen" zB 5��,�lh��}��'�O8��m�h,� Mit einem anderen Sketch funktioniert der Sensor einwandfrei. Auch mit einem anderen Nano dasselbe Ergebnis. Hat jemand eine Idee was das Problem sein könnte? Zusatzfrage da ich in C++ nicht so firm bin: Könnte es sein, dass MY_DEBUG oder MY_RADIO_NRF24 das problem verursacht. Was machen diese Definitionen eigentlich? Grüße
Long time test done with soil sensor!
My Project • 7 Jan 2025, 09:13 • Nicklas Starkel 13 Jan 2025, 09:10

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Wow @Nicklas-Starkel congrats, that sounds great! And thanks for the feedback. Would you mind sharing your setup? Regards, Edi
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My Project • 31 Dec 2024, 17:52 • nagelc 25 Jan 2025, 20:21

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25 Jan 2025, 20:21

Quick Range Check on the WIO-E5-LE. The LE version uses only the low power PA, +14dBm max. Using the default settings except for 915MHz #define MY_SX126x_FREQUENCY (SX126x_915MHZ) #define MY_SX126x_LORA_SF LORA_SF7 #define MY_SX126x_LORA_BW LORA_BW_125 #define MY_SX126x_LORA_CR LORA_CR_4_5 I get about 190 meter range, just walking around the neighborhood, line of site except for some trees and power lines. No tuning on the antenna. Just using a 77.9mm wire. Not as dramatic as some have achieved with LoRa radio's, but plenty good enough for my house and yard : )

Capacitive Soil Moisture Sensor

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Capacitive Soil Moisture Sensor

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Welcome Announcements • 23 Mar 2014, 08:24 • hek 2 Apr 2014, 14:39

A low cost energy meter My Project • 25 Jan 2024, 01:03 • OldSurferDude 12 Aug 2024, 06:03

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BMP280 SPI Adafruit My Project • 24 Aug 2016, 01:56 • Matt 23 Jan 2025, 16:25

Long time test done with soil sensor! My Project • 7 Jan 2025, 09:13 • Nicklas Starkel 13 Jan 2025, 09:10

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Announcements • 23 Mar 2014, 08:24 • hek 2 Apr 2014, 14:39

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My Project • 25 days ago • Paul Scarbro 22 days ago

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