The 1-wire soil moisture sensor circuit I use in my garden is designed by Eric Vickery from http://www.hobby-boards.com.
(c) 2006 Hobby Boards Designed by Eric Vickery
Title: Moisture Meter 3
Date: 10/27/2006 06:11:30p
(Click the picture for a larger version.)
Here’s a bit of explanation on how the soil moisture sensor circuit works.
The circuit is connected like this:
- Watermark soil moisture sensor: Pin 4 and 5
- 1-wire network: Pin 1 and 2
- 12 volts power supply: Pin 1 and 3
and the circuit works like this:
- Watermark sensor gets wet
- The time constant of oscillator IC 555 changes
- 555 IC oscillates faster and its supply current goes up
- Current in resistor R2 goes up causing the voltage across R2 to go up too
- The value of the current register of IC DS2760 changes
- Current register of IC DS2760 is read via 1-wire network
In my case I got the following values during calibration. I let the Watermark sensor dry in the wind and recorded the current register value, and afterwards the sensor was soaked in a bucket of water:
Dry = -0.2368
Wet = -1.400
These numbers form the 0 and 100 % limits of my soil moisture readings:
17 comments on “Soil Moisture Sensor Circuit Explained”
Quick question. What type of data is provided for the output? Is it serial or a square wave? Please let me know, I want to send the output to a transducer or a pizzo for a simple alarm when the saturation point is reached. Thank you for your time and consideration in reviewing my request.
@Dennis: As I see it the “output” of the circuit is a software register.
I think what you need is an OpAmp Schmitt-trigger measuring the voltage across R2, and removing U1, R1, C3 and D1, but I’m not sure if that’s what you want?…
Hi, I want to do this circuit, but in dallas website, the ds2760 is no loger available, I could change the ds2760 to ds2762? thanks, best regards
@Braulio: I think you can use DS2762 instead as the manufacturer Maxim states, “DS2762 is an update to DS2760”.
I require to measure water content at root zone of plants. What material shall be used as a probe. whether still wires will work.
@RD Pawar: Please take a look at this post: http://veggiegardenideas.com/2008/12/23/soil-moisture-sensor/
I want measure soil moisture n give its output to controller.I had made one circuit but it is giving me output even at low humidity.I want to compare present moisture value with threshold value.how can I do that?.thank you for giving your time and consideration.
@Riteeka: What type of controller do you want to use, and what does your circuit look like? Do you have a schematic? What sensor are you using?
hi Tom,its Mpho in Botswana,one country in southern Africa..i need some assistance from you,i want to design a circuit which control the moisture content,pliz send me some possible circuit diagrams
@Mpho: What device / component will you be using to control the water flow? Some kind of pump or valve? I plan on using an electric drill pump (Gardena, 1,700 l/h @ Ø 13 mm hose, 3 bar) connected to a sprinkler or soaker hose depending on the crop (some crops are sensitive to water on their leaves due to blight.)
sir..how i want to control the soil moisture sensor?can i use the microcontroller?can u recommended what type of microcontroller?my project is about solar system for irrigation that using soil moisture sensor..
@Hazil: I think you can control 1-Wire devices with the Arduino board. I’m using NSLU2, but a SheevaPlug or FitPC should be able to control it to.
sir, can relay switch and timer can be added to this circuit?
@Hazil: Yes – the voltage across R2 could be measured by the input of an opamp comparator and then a switch actuator could be added like in this circuit: http://66pacific.com/ph/phschematic.htm (Valve solenoid = relay coil)
An extra 555 IC can work as a timer IC: http://www.kpsec.freeuk.com/555timer.htm#monostable
Sir I want to analyze the content of soil. (Phosphorous, Calcium etc) so can you suggest any kind of sensors for the same? If I could make some on my own would be great for me to learn. Thanks.
@Mahesh: The only way I know about is to use a kit like this for example:
although it would be cool to have sensors for that too.
hello,can I have the email address of Thomas W I need help with my soil moisture design.