Irrigation control with input from soil & weather data

[salesguy]

I am getting ready to write the code for my irrigation controller using the webcontrol board. I have a SSR setup and wired to control the solenoids and I'm moving on to the next step.

I'm wondering if anyone on this board has used this board for this use?

If so - how have you used soil moisture sensors? How about google weather data?

The soil sensors I have work well with the board, they output an analog signal and I can easily use it as a way to block the scheduled watering for a specific zone.

I was also looking to use the google weather API to integrate current & near future weather data to adjust the watering. I would have to do it with my arduino, because I can't do it with webcontrol. I was thinking that the arduino would set a variable with a range from say 0 to 10 and then add that into the mix.

Thanks!

 

[fwd03]

I read somewhere Homeseer integrated this board with their irrigation control logic. Someone else also mentioned using WebControl to control the irrigation on this board, but that was sometimes ago. What kind of soil moisture sensor do you use?

 

[salesguy]

Gotcha. I'm using a cheap sensor like this one:

http://www.ebay.com/itm/Soil-Moisture-Sensor-Self-watering-Automatic-Irrigation-Garden-Tool-for-328-2560-/150846065075?pt=LH_DefaultDomain_0&hash=item231f2049b3

 

[fwd03]

I brought this one from Amazon:
http://www.amazon.com/BestDealUSA-Plant-Flowers-Tester-Moisture/dp/B006KY5OUG/ref=pd_sim_hi_3
Then I opened its back and run two wires from the meter to webcontrol analog input. In dry condition, the voltage crossing the meter is 23; in really wet condition, voltage is about 57.

What kind of reading do you get with your sensor?

 

[salesguy]

Huh, that is a pretty small range.

Mine has a range of 0 to 600, wrapped in wet paper towels it's somewhere in the mid-range.

I haven't decided if I'm going to use multiple sensors and get readings from various zones or just use one.

I also don't know if longevity will be improved if I only send voltage through it when I want a reading, or if all the time is ok.

 

[apostolakisl]

Huh, that is a pretty small range.

Mine has a range of 0 to 600, wrapped in wet paper towels it's somewhere in the mid-range.

I haven't decided if I'm going to use multiple sensors and get readings from various zones or just use one.

I also don't know if longevity will be improved if I only send voltage through it when I want a reading, or if all the time is ok.

The only possible thing I can think of here is mineral deposits. With electrical current present it may cause more deposits to occur? Just a random thought with nothing to back it up but some wild thoughts of positive and negative ions sticking to the negative and positive terminals of the sensor in the ground.

But I have to say, it appears to be quite nicely suited to the webcontrol board.

As far as getting weather related data into the cai like forecast or other weather data from google or someone else. You can post values to cai's variables using a simple http command. So, you would need to have an application running on a separate computer that queries the data from the weather source, and then plugs the values into a post command setting certain variables on the cai. Then it is just a matter of incorporating those values into your plc algorithm.

 

[salesguy]

Agreed.

I was thinking of using my arduino or maybe writing some perl script running on my router to query the google weather API, and then based on the response generate a score or weighting based on the response.

That part I'm not completely sure on yet, but I did confirm yesterday with someone who installs commercial systems that they almost always use a combination of humidity, temperature, soil moisture, current conditions (ie, rain) and forecast to determine if watering is needed or not. He was very impressed that a homeowner would have this capability, even more so when it was homemade.

Now i just have to make it work well!

 

[apostolakisl]

They call that evapotranspiration. It is very complex to calculate as you must know so many variables such as hours of sunlight and the intensity of sunlight (cloudy at 1pm is not same as cloudy at 5pm), wind direction/speed, soil type, and foliage.

Direct measurements of the soil are much simpler provided your measuring device is accurate. Keep in mind that different parts of your yard will dry out faster depending on their exposure and soil types.

If you can measure soil at representative locations around your yard and get accurate readings, that should pretty much be everything you need. Adding forecast data into the mix might help, but frankly, forecast data usually stinks. For example, the LCRA who manages the damns on the lake system here, has a policy to pay zero attention to the forecast. They open damns 100% based on the rain that has already fallen.