I’ve done a bit of planting this season, mostly by hollering at helicopter students to dig. So far we have about 1500 new plants in the ground and therefore it is time to think about irrigation. Given the high cost of water, either paid directly to a municipal water company or to the electric company when pumped up from a well, I figured it would be easy to find a smart spigot-end controller/timer. My timer would measure temperature, light, humidity, and rainfall then irrigate accordingly. I.e., it would shut itself off on cold damp days and run longer on hot bright dry days. As the controller/timer is already out in the elements, all of the sensors can be mounted directly on/in the box. Amazon sells desktop digital temperature/humidity sensors, complete with LCD screen and battery holders (parts already required for the controller/timer) for less than $10. So you’d think that a $40 or $50 hose-end controller/timer could have at least some of the obvious sensors. But they don’t. A friend pointed out that Make published an article on a home-made system that does some of this (link). But I’m surprised it isn’t offered at Home Depot.
19 thoughts on “Suburban irrigation done with maximum waste due to primitive control systems”
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There are rain sensors that can be attached to commercial timers. The rest of the ideas seem like they are overly complicated for the task. Commercially available timers can already be programmed using software on a PC then uploaded to the timer. You vary the delivery of water by time of day, length of time, station, day of week, etc. You can vary flow rate to particular plants by the type of head. I think this is a perfect example of the product not being available not for lack of ability of an engineer to create it, but because the benefit is very marginal. The average consumer can barely program the timer they have.
I met someone once who had a small business doing PLCs for irrigation automation on large farms. That’s apparently how the pros do it.
How is your hypothetical device powered? Solenoids can be power-hungry so some kind of solar-cell+SLA battery combo is likely to be a marginal performer in most of the country, and relatively expensive. You’d probably end up running conduit to the box anyway, so I don’t see the advantage of putting everything in one box and dealing with weatherproofing/leakproofing issues.
Oh, I just googled hose-end timers: they make ’em that run off disposable batteries. Never mind on the power issue.
Jim: I have seen rain sensors that connect to the central irrigation controllers designed to run 10 or 20 different zones. But even those fancy controllers don’t seem to take temperature into account. Here in Massachusetts we can have a 50-degree day adjacent to a 90-degree day and the water needs are hugely different. As far as the challenge of programming goes, I don’t think it needs to be be any harder. The controller could have one option for weather compensation on/off. Nearly all plants will need more water on hot dry days than on cold wet days.
Brent: The controllers that Costco sells for $33 have an LCD screen, a big wheel switch and some navigation buttons for programming, and come with two AA batteries. I’m assuming that the batteries will last for one season.
It seems a lot easier to write a script which will pull a report from a nearby weather station (which is probably just a few feet away in your case 😉 and control the water flow accordingly. hopefully a remote controlled pump is not an issue.
Hey Phil,
I don’t think that you need all of the sensors that you’re thinking about. Ultimately, the plants need a certain level of moisture in the soil to thrive, and so the sophisticated irrigation systems use a soil moisture sensor such as:
http://www.rainbird.com/landscape/products/accessories/smrty.htm
Heat, low humidity, lack of rain, or lots of sunlight can all deplete the soil moisture, and so you could measure those and make a model of how those affect the soil moisture, but it’s easier just to directly measure it. Personally, I use one of these:
http://www.toro.com/sprinklers/timers/ecx/access_wiredsensor.html
Which is a little less sophisticated. It sits out in the weather, and has some porous fabric discs in it. When it rains, they get wet and expand, and when it’s hot and/or dry, they dry out and contract. The discs push up against a microswitch, which is adjustable. When they are wet and push the microswitch, it inhibits the sprinkler controller. Most sprinkler controllers have a sensor input which is binary, and they will not water when the sensor input is on. This lets you schedule the sprinkler for the morning on the legal days, and then if it’s too wet, the sprinkler just doesn’t run.
I’ve tried battery powered hose timers in the past, but was dissapointed when the life (2 AA sized) was only about 2 days. Perhaps the tech has improved since then (about 10 years?) I know NiMH energy density is several times that of NiCad, but still…
I now use mechanical timers (Vigoro Model 3010V) from Home Depot for my 1/4″ drip irrigation lines. The sensor is me. I crank them on in the morning on my way to work if, the soil is dry, the weather, warm, or the plants are looking droopy.
presidentpicker: If the U.S. had invested in a wireless Internet that was free for low-speed uses (rather than in freedom for all Iraqis and Afghans), I think that your idea would be a great one. But as it happens, the $33 irrigation clock would need a $40/month cell phone data service subscription in order to get a few hundred bytes per day of weather info (and in fact there is no cell phone service in my yard). So for a non-networked country, I think built-in sensors are a better choice.
Dave: Thanks for the links. I don’t see how those are going to trickle down to the hose-end controller/timers any time soon, though. I guess a wired soil moisture sensor might be the best thing, but I still like the idea of just adding $10 of sensors to the $33 box that sits at the spigot.
Home irrigation systems are annoyingly primitive.
I have 4 valves to control (yard plants, daily flowers (it’s Arizona), citrus trees and veg garden.) I could not find an affordable (< $125) controller to do all 4 of them. Now there are controllers (including mine) that control more valves than that, but there are only 3 programs you can use! Does it take that much more FPGA or uController space to have 4 or more programs? The relays and other electronics are already there to turn on 6 different valves.
Temperature/humidity seem like luxurious features after not being able to control a basic number of valves.
The UI's are horrible.
It’s not just home irrigation systems that are primitive. Here in San Francisco the city seemingly is watering its parks using a simple timer, rain or shine. I’ve seen the sprinklers going on full blast while it’s pouring rain. And this is at a time when we have a severe drought here in California.
Didn’t see the hose-end part, but sensor capable hose-end systems do exist.
http://www.amazon.com/Claber-8410-Aquadue-Duplo-Water/dp/B000EVQ0O0/ref=pd_rhf_p_t_3
http://www.dripworksusa.com/store/btimers.php
(Scroll down to “Low Pressure Battery Timer”)
I believe that all of these use a simple two terminal switch type connection to the rain sensor, so you can use whatever type of sensor is convenient.
You won’t need a cell phone data plan for each of your hose’s ends. 🙂 What I think may work is a script running on your home pc which is on and internet connected, presumably, for other uses. This pc will control a valve at the water source via x10 or some other suitable protocol. My outside lighting is controlled this way – a bit of perl calculates sunrise/sunset and pulls cloud cover percentage from noaa. This is enough info to set ouside lights brightness (although Dave might argue that it’s easier to measure the light level directly)
Most suburban irrigation is 100% waste, since it goes toward a crop that has no industrial use and that neither humans nor livestock can consume. The only way to improve the useful efficiency of suburban lawns would be to start hunting Canada geese on an industrial scale.
Thanks, EZ. Your comment reminds me of the management consultant hired by the symphony orchestra. He pointed out that all of the violins typically played the same note, so that they could reduce staff levels in the violin section to just two employees. He also noticed that many pieces included some repetition, so a Beethoven symphony could be performed in just 5 or 10 minutes if the repeats were eliminated.
I seem to recall from a discussion about pan evaporation (http://en.wikipedia.org/wiki/Pan_evaporation) that solar energy had a greater effect than temperature. The noted drop in the pan evaporation rate over many decades was attributed to global dimming even though average temperatures have been rising.
Some ET controllers can receive weather information via free radio signals:
http://www.rainbird.com/landscape/products/controllers/etmanager.htm
A discussion of ET and other smart watering technologies is available at:
http://www.terrylove.com/forums/showthread.php?15722-weather-smart-irrigation
A rather complete comparison of various commercial offerings was done by the U.S. Department of the Interior Bureau of Reclamation:
http://www.usbr.gov/waterconservation/docs/SmartController.pdf
Thanks, Patman. Now we just have to wait for that technology to trickle down (so to speak) to the hose-end battery-powered boxes.
I have all of these sensors built in, and at no charge and no battery replacements needed.
I have my irrigation system water a reasonable amount every day. When its been hot for a while, I go out and push the button to have it do a second watering every now and then. If it turns cooler, I turn the controller off for a while.
Funny business aside, I live in a part of california where its 100 degrees and dry for ~5-6 months out of the year and 50 degrees with pouring rain the rest of the time. Its also fashionable to have extensive lawns, fruit trees and shrubbery even with $200/mo water bills. So I have some experience with irrigation.
Your biggest practical problems have little to do with when the controller turns the water on and off and everything to do with an adequate but not excessive amount of water thats delivered to each plant. Soil depth and content from one side of your yard varies greatly from another. One shrub thats a little bigger than its neighbor needs more water. That tree over there really doesnt need any since its developed a deep root system and has deep soil under it.
The biggest implementation problem is using cheap or inadequate components that are buried in the ground or using above ground broadcast spray irrigation systems that lose much of their water to evaporation and water dirt with no plants nearby to make use of it.
Many of the systems around here were built from in-ground pvc pipe that is ridiculously thin-walled (its a few dollars cheaper) and instead of a quality flexiline to connect from the pipe to a drip or spray fixture they used a flimsy piece of plastic hose. As a result, almost everyone in the area has cracked main pipes and flexilines with holes/tears in them or they’ve mostly slipped off.
As a result, as much as half the water issued by the controller is discharged into the ground to no benefit.
So saving water might have a lot more to do with using the right methods of water delivery and a quality of construction that stands the test of time, where ‘time’ is longer than 5 years.
Most of the water-sensing irrigation systems don’t work well. One of the best systems out there is built by an Electrical Engineer who left HP and started his own company. They remain a very small company, but they have great technology. The company is called Acclima http://www.acclima.com.