Who accept a challenge to write plugin with soil moisture?

[Dan in CA]

Hi Mike,

Looks like the link you posted has the sensor end of things pretty well covered. The problem would be connecting both an xbee and the OSBo board to a BBB. A quick internet search brought up some links to an xbee cape for the BBB but it looks like that would preclude connecting the OSBo board unless you figure out how to use cables to make the connection.

If you figure out a way to have both the xbee and OSBo board connectd it should be pretty easy to write a plugin for the ospi software to handle controlling the irrigation.

Dan

 

[Mike]

I’m thinking of stackable headers sticking out of the bottom of the OSBo instead of cables.  That’ll mean a new enclosure but I was planning to put the whole thing into an outdoor enclosure anyway.  I’ll start acquiring parts over the coming weeks.

[tom]

The challenge isn’t just getting the sensor to work, but rather if the sensor is actually measuring anything useful.  Soil electrical conductivity varies with the salts in the soil more than the moisture.  Fertilizers, salt buildup, etc. all have a huge effect on the reading.  And the salinity also affects the ability of the plants’ roots to extract water.  So, a higher conductivity might mean that the plants are less able to use the water in the soil… exactly the opposite of what we are trying to measure.

And, assuming we had a valid sensor, it would be hard to extrapolate from that sensor to the soil around it.  Imagine a tree with a line of drip sprinklers spaced at 18″ intervals.  If the sensor happened to be directly under a drip outlet, it would show a drastically different reading than one 9 inches away.  Check out http://www.soilmoisture.com/ for more information.

An alternative might be to measure micro climate factors, such as shade and soil temperature.   Lawns might be shaded in the winter in yet full sun in summer, or trees might be shading the lawn in one season and not another, etc.  A simple soil temp probe or maybe solar radiation could be used to modify the zone’s ETo numbers.  Then the problem becomes how to change the sprinkler zone’s behavior as its micro climate changes.

[Mike]

The VH400 doesn’t measure conductivity.  Sounds like that’s a good thing.  Since it can be buried the moisture differences between drippers can be mitigated pretty well because the water will spread out once it enters the soil.  I definitely agree that the position of the sensor is important, so point taken there.

However, I’d much rather measure soil moisture directly than try to predict it with alternative measurements.

[Michael]

Hi All,

I am new to this forum and came across it in my endless pursuit to design and build the most efficient sprinkler system possible. While I have not used any of the OpenSprinkler controllers yet, I am considering it if it can solve my dilemma. I would like to be able to use a soil moisture sensor for each one of my irrigation stations as a secondary water saving device. Currently, I am using the TORO Evolution controller with the EVO weather sensor, which allows me to program my schedule based on historical weather data, then it will adjust based on current conditions (temp, humidity, freeze stop, and rain delay). The rest of my system is using all Hunter MP Rotator heads, Hunter PRS40 nozzles with check valves, and Netafim Techline CV (can’t get more efficient than that so far as I know). While this is all great, I still believe I can save more water, which is why I am looking at soil moisture sensors.

What I would like to do, is use my current system to set the schedules and determine the maximum amount of water my landscape receives. Secondly, I would like to find a soil moisture sensor product that simply measures the moisture, determines if it is adequate, and if it is, shuts down the watering. It may not even have to communicate with the controller, but rather serve as a bypass switch that blocks the controller signal from the valve.

Does anyone have any ideas of how to make such a system work?

Thanks,

Mike

[Mike]

I’m still working on pulling together a parts list and planning the details for the sensor side of things.  Here’s my list so far:

Moisture Sensor $37.95  XBee $22.95  Solar Panel $25  Battery $12.50  Solar Battery Charger $17.50  Adjustable Voltage Regulator $5.95 XBee Breakout Board $2.95 some XBee Headers $2 and miscellaneous resistors, wires and an NPN transistor which I have on hand.  This is how I’m thinking I’ll wire it up.  Thoughts?

I’m using an OSBo so I’ll also have to hook an XBee up to my BBB but that should be much more straight-forward with a cape and some stackable headers.

 

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[Dan in CA]

Thanks for the update.

I’m sure there are a lot of folks who will be interested in your progress.

Dan

[Hiouchi John]

Great work Mike, very inspirational.

I’ve been searching for a while for an irrigation controller that also uses moisture sensors. For my needs, I want to have 1 moisture sensor per valve. I really don’t care if I have to run wires, as that is less batteries to replace, however wireless options would be great as well.

I like the direction that you are going with your project, however if I could make a suggestion, with the costs you have detailed above, that it would be fairly costly for me to have 1 sensor per valve. A 10 valve system could be nearly $1000 to automate with your sensors.

(before I found this thread) I had ordered a moisture sensor system from a new startup, plant link. Not sure how well they will work yet as they haven’t arrived but on a cost comparison the wireless sensors are priced at $35 each, though you do need a slightly more expensive base station as well. (and all they do is moisture, no sprinkler control)

 

The moisture sensor that you have chosen looks awesome, however is there a reason that you went with it and not one of the cheaper ones? something like

http://www.amazon.com/Arduino-compatible-Sensitivity-Moisture-Sensor/dp/B00AFCNR3U%3FSubscriptionId%3DAKIAILSHYYTFIVPWUY6Q%26tag%3Dduckduckgo-d-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB00AFCNR3U

 

Is there an easy way to integrate the moisture sensor with wires to the OSPi? and why the pi and not the regular open source sprinkler kit?

I want to buy an open sprinkler however should I go with the regular or pi version?

 

 

[Hiouchi John]

Also, I am interested if temp, humidity, and light sensors could be added as well

Thanks

Keep up the good work

[Mike]

If you are willing to run wires, you might be able to do something like this relay board with the moisture sensor.  I don’t think any programming would be required, just hook it up like the diagram shows and set your schedule.  When it’s time to water, the relay board will get energized and if the soil moisture is low enough the relay board will open the sprinkler valve.  Pretty slick.

To be honest, cost is the biggest thing I’m struggling with now.  It’s far more expensive than I want and the single highest cost item is the moisture sensor I have chosen.  I do think it’s the right sensor though.  From what I’ve read about the sensors of the type you have linked, they’re not durable.  I’ve never used one though.

I want wireless because of the flexibility and because wire is expensive too.  I’m going to be using it in my gardens and I like to move stuff around.  I might want it in one garden one year and another garden the next or in the tomatoes one week and the dahlias the next.

The XBee has four analog to digital converters – which basically means that I can read 4 values at each remote station.  The moisture sensor will be one of them.  Battery voltage will be another.  I was thinking about soil temperature and a light sensor for the other two values but I’m kind of focused on the soil moisture for now.

[Hiouchi John]

Thanks for the link. I just checked that out and I think I might buy one to test out. Its half of what I want to happen. So thats not bad. I do like how it will allow the valve to turn on when you hit a desired dryness. Edit.What I wish it would do is in addition to turning on when dry it would not turn on if too wet. That way it stays in a range of moisture. Other improvements would be digital control instead of the variable resistor and logic that allowed the sensors to fully control the valves instead of the sprinkler timer. Ie: maybe the plants want water twice a day some days and other days once, or maybe they want water every 14 hrs for the first month and then water every 9 hours the second month. The acceptable range would allow the plants to govern when they wanted water.

I grow in a greenhouse, with beds. The last two years my strawberries have fried out as I’ve been trying to conserve water due to the drought. With so many types of veggies and a hectic schedule stuff just gets watered unevenly.

 

I plan on buying an opensprinkler. Since I am interested in integration with sensors. Is it a wiser decision to buy the pi version as it has a greater chance of being future integrated with sensors?

 

Thanks

 

Edit, after thinking about this for a while I realized my logic was wrong and the feature of turn on if dry does create a range. As buying 1 relay per sensor is still kinda expensive if you scale out, is there a way to build a version of the relay you linked to but with support for more sensors and valves but still one sensor per valve? hmmm

[Mike]

I’m in the process of building my first greenhouse.  It’s taking up half of my garage right now.  That’s holding me up from working on this moisture sensor project.

It sounds like you may not need any OpenSprinkler product.  Just run 24 volts to the relay control board with a moisture sensor attached.  If it’s dry it’ll turn on.  If it’s wet it’ll turn off.  Very simple.  You’ll only have one on/off threshold though.  Would be better to have separate on and off thresholds.  That would help avoid short-cycling.  Bury the sensor deep enough though and it may be all you need.  My plan with the moisture sensor integrated with my OSBo is to have the moisture sensor trigger when to start watering, water for some adjustable amount of time and then shut the water off.  That’ll all be handled on the software side of things.

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