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Soil moisture sensors better than ET for irrigation

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    #61
    Originally posted by Automated View Post
    Where can one pick these up for 30 each! I might get a few to play with at that price.

    Edit: On the other hand Amazon reviews are not too promising. It will be interesting to hear your long term review of these.
    It was jumping the gun, but purely to lock-in the price I ordered another seven units on Monday from an Amazon seller (the same one who sent me the first three units):

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    Not sure if it's related, but that seller subsequently raised his price by $10. Some of what he shipped me had Home Depot mark-down stickers on them. Because there are so many Home Depot stores in the country, I would guess there are still many more units out there that will be liquidated, thereby continuing downward pressure on market pricing.

    Regardless, many have been sold on Ebay recently at close the same price I paid. There's not a huge float, so you may just need to wait until Ebay finds you a unit at a price you like.

    Also, I have since then uncovered some flaws in the design. I have to run now, but I'll post later today or tomorrow to elaborate.
    Last edited by NeverDie; April 12, 2014, 04:21 PM.

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      #62
      Some potential flaws I've uncovered are:
      1. If power is lost to the receiver, the receiver will attempt to recalibrate some time after power is restored. However, the calibration routine assumes that the soil is at field capacity at the time of calibration, and there's nothing to guarantee it will be. Powering the controllers through a UPS would mitigate this problem.
      2. If for some reason, communication is lost between the sensor and the receiver for an extended period of time (I seem to recall 24 hours), then bypass mode is engaged and the controller will no longer inhibit irrigation (presumably until communication is restored). I can foresee scenarios where this behavior could be problematic: underwatering won't be a problem, but overwatering might become a problem if not supervised.
      3. The soil moisture sensor's reading is adjusted to compensate for temperature. However, it should be compensating for soil temperature, and my measurements indicate it may be reading the case temperature, or possibly air temperature, or maybe some conflation of the two. The result is distorted moisture readings, especially when in direct sunlight.

      I'm most concerned about #3, but I haven't yet decided whether it's a fatal flaw or whether it might be worked around.

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        #63
        Originally posted by NeverDie View Post
        Some potential flaws I've uncovered are:
        1. If power is lost to the receiver, the receiver will attempt to recalibrate some time after power is restored. However, the calibration routine assumes that the soil is at field capacity at the time of calibration, and there's nothing to guarantee it will be. Powering the controllers through a UPS would mitigate this problem.
        2. If for some reason, communication is lost between the sensor and the receiver for an extended period of time (I seem to recall 24 hours), then bypass mode is engaged and the controller will no longer inhibit irrigation (presumably until communication is restored). I can foresee scenarios where this behavior could be problematic: underwatering won't be a problem, but overwatering might become a problem if not supervised.
        3. The soil moisture sensor's reading is adjusted to compensate for temperature. However, it should be compensating for soil temperature, and my measurements indicate it may be reading the case temperature, or possibly air temperature, or maybe some conflation of the two. The result is distorted moisture readings, especially when in direct sunlight.

        I'm most concerned about #3, but I haven't yet decided whether it's a fatal flaw or whether it might be worked around.
        According to the manual it does indeed use air temperature. I think I might skip this one. As I already run Davis weather here, I am able to use their soil sensor add-on which measure actual soil temp.

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          #64
          I may have buried the one Toro sensor too deeply, because it never showed much moisture drop even though the unburied ones did, as did a portable test probe I've started to use. It does show a comparatively constant temperature range.

          So, this morning I took one of the remaining two and buried it more shallowly. It's fully buried, but it should track moisture at about 3" below the surface, as compared to 8" below for the one I buried earlier. I'll compare their readings, along with the other one, to see if it makes a difference.

          Also, another potential "gotcha" is that it doesn't go back to the mode where it blocks irrigation until its calibrated soil moisture reading rises to 90% or more. So, for instance, it wouldn't block at 89%, and so the next irrigation might result in a lot of waste if it was a lengthy irrigation cycle. I may be able to work around it, but I really wish they hadn't done it that way.

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            #65
            How's it working out for you.

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              #66
              I've been irrigating based on soil moisture, and it does seem to be saving me a lot of water (with no visible negative impacts on vegetation) versus purely timed waterings, which is how I was doing it before. I'll have a better quantitative grasp of that when I tally this summer's water bills and compare against previous years.
              Last edited by NeverDie; June 17, 2014, 06:48 PM.

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                #67
                I did this already, and it works fine.

                [QUOTE=NeverDie;1115072]I'm not aware of anyone having tried the experiment, but it would seem possible over time to generate corrective correlations. Depending on the number and placement of your soil moisture sensors and weather instruments, the weather station ETo data might be, to varying degrees, either redundant or essential (or possibly irrelevant if the data contains too much noise).


                I have a (actually three) Davis Pro Plus with a leaf/soil station. I am a Texas Master Gardener/ Certified Arborist, and I Own a Company Called Real Green Pest and Lawn here in Austin. We are not a mow and blow type company but a fertilization and weed control business. I have about 32 trucks and we service about 5k lawns on a recurring basis, 10 times per year. www.RealGreenLawns.com

                I have been involved in Automation since the late 80's. That's right, like 89? Anyway, My setup at my home is 5 ezfloras, ISy995, Elk, Homeseer, Davis, yada, ya.... Anyway, I hate ET. Its not accurate, because its not predictive. I had been doing all my irrigation thru the ISy based on Et. But because of weatherbug and their changes, I went to what I have been doing at my office, for my home. Which is take the soil sensors (4 of them) one in my rose garden, one in my vegetable garden, on in some herbs, and lastly one in the lawn. Also know that this maxs out the davis station. To have more, you have to go to the envoy 8x. Which is a major pain, because of the export protocol. SQL.

                For most people, a rain flag set to .25 inches, triggering a 30 hour delay when daytime temps average above 65 works fine with ET. But, ET isn't constant... So then you get to the predictive part of "if chance of rain > than 40%.... And all this mess works mostly fine, if you know the output of your irrigation heads/zone. http://www.youtube.com/watch?v=0k3np...=share&index=7

                Yes, that's me....

                Anyway, if you take the Davis moisture sensor and insert it in the ground, at a 45 degree angle, down to where the top is about 3 inches from the soil surface, you will get a good reading. But still, you have to do all the ET stuff, Rain stops and prediction. You cant do this instead of, you have to do it in addition to and you will have a more accurate irrigation cycle. I have some of those Davis sensors that have been in the ground for over ten years, with no problems, what so ever.

                Biggest problem is the zones themselves. Most are installed geometrically, with all the heads outputting the same, sun and shade. Simply measure the output in various areas of the same zone and swap the nozzles to compensate. Basically, you can figure full shade will use about 60% of that in full sun, given the obvious. (slope and soil composition.) Beyond that, don't over think it and don't buy your nozzles at Home Depot. Go to an irrigation supply house, where you can spec the flow and radius. Or better yet, go to http://www.sprinklerwarehouse.com/Default.asp

                And yes, everybody's soil, weather conditions and turf types will be different... But still: its all basically the same. Spend 12 dollars on a moisture meter, until you get it dialed in. Or better yet, get yourself a flower power, from parrot. I have a few and am always moving them around.

                Anyway, I had been following this thread and I had to chime it.... Sorry for all the words. G'night.

                Jerry

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                  #68
                  Originally posted by jnaiser60 View Post
                  Biggest problem is the zones themselves. Most are installed geometrically, with all the heads outputting the same, sun and shade. . . .And yes, everybody's soil, weather conditions and turf types will be different... But still: its all basically the same. Spend 12 dollars on a moisture meter, until you get it dialed in. Or better yet, get yourself a flower power, from parrot. I have a few and am always moving them around.

                  Anyway, I had been following this thread and I had to chime it....
                  Jerry
                  Jerry,
                  Thanks for the great insights. I definitely agree that zone layout can be a major barrier to irrigation predictions and strategy. Right now I have a zone with standing water at one end, and dry soil at the other! In the fall, the whole zone will have much more uniform water loss, but when the water table is high there is no way to run the zone intelligently. Although that's an extreme example, I'd say that at least a quarter of my zones suffer from the same problem to some extent. In addition, the effects of moving sun and shade patterns and tree transpiration variation from leafless to fully leafed also cause seasonal shifts in the ET calculations and wet/dry patterns within zones.
                  Mike____________________________________________________________ __________________
                  HS3 Pro Edition 3.0.0.548, NUC i3

                  HW: Stargate | NX8e | CAV6.6 | Squeezebox | PCS | WGL 800RF | RFXCOM | Vantage Pro | Green-Eye | Edgeport/8 | Way2Call | Ecobee3 | EtherRain | Ubiquiti

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                    #69
                    Splitting the zone can solve your problem. Take a look at an irrigander. I heard the company might be in trouble, but the product is still readily available. They are rock solid. I used them to grab an extra eight zones from two wires. What you do is unhook your furthest zone valve wire, make it hot with 24v. Add an irrigander 2 zone receiver at this furthest zone. (Wether you need it or not) what your doing is saving the trouble of running valve wires. If your irrigation system was installed properly, your zone wires should be run beneath your main line. The irrigander is nothing more than a power line carrier device over the 24v. Now with this set up, you can pull a zone from wherever you want. http://www.smarthome.com/3138/DuWa-2...plitter/p.aspx

                    Jerry


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                      #70
                      Ignore that link.... Here is the right one.. http://www.smarthome.com/31383/DuWa-...xpander/p.aspx




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                        #71
                        Originally posted by jnaiser60 View Post
                        Splitting the zone can solve your problem.
                        Don't think I haven't considered that. Actually, in my case I don't think the wiring is the biggest problem. I can probably recombine heads to keep the number of zones the same, but changing the connections to the affected heads will not be trivial. In any case, it's only money. (I don't have any interest in doing it myself.) While that will certainly improve the situation for some of the zones, I wouldn't go so far as to say it will fully resolve it.

                        My point, though, is that no zone is truly uniform, either spatially or temporally. Some are better than others, but all require some compromise. That's especially true when you overlay watering restrictions that often cause soil moisture levels to fall much lower than desired between cycles.
                        Mike____________________________________________________________ __________________
                        HS3 Pro Edition 3.0.0.548, NUC i3

                        HW: Stargate | NX8e | CAV6.6 | Squeezebox | PCS | WGL 800RF | RFXCOM | Vantage Pro | Green-Eye | Edgeport/8 | Way2Call | Ecobee3 | EtherRain | Ubiquiti

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                          #72
                          Yes, I agree.


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                            #73
                            Micheal, an easier approach then splitting the zone would be to swap out the nozzles on the rotary heads.

                            In a wet area place a nozzle that outputs 1 GPM and the drier area a nozzle that outputs 4 GPM. Those might not be the exact nozzles needed but that's the easiest way to tune your zones.

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                              #74
                              Originally posted by CharlieWayne View Post
                              Micheal, an easier approach then splitting the zone would be to swap out the nozzles on the rotary heads.
                              I do something similar on one of the zones, but the problem is more complicated because the differential water needs between parts of the zones varies by season. I'd prefer not having to swap heads as the summer progresses.
                              Mike____________________________________________________________ __________________
                              HS3 Pro Edition 3.0.0.548, NUC i3

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                                #75
                                Originally posted by Uncle Michael View Post
                                I do something similar on one of the zones, but the problem is more complicated because the differential water needs between parts of the zones varies by season. I'd prefer not having to swap heads as the summer progresses.
                                So you just need a Zwave, variable flow sprinkler head is all..

                                We only do drip irrigation, so "sprinkler" heads are easy, and cheap (.25)

                                Z

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