Water content sensor networking to automate watering

If been asked by a grower with 5 cultivation centers to develop a low cost version of Grodan’s GroSens rockwool moisture monitoring system. He got a quote for $26K for 24 systems. He wants 60 for a 15K plant grow. We believe we can get the unit cost down under $100 and hopefully closers to $20 per rockwool 6" cube sensor. Each sensor will have an array of frequency domain capacitance type sensors to map the water density gradient of the whole cube. We will then collect the data throughout to grow to uncover the optimal points of watering. This grower uses cubes on flood tables, but the system should work for drip and wick systems using cubes or slabs. It should also work in other media and solids. We will also measure rockwool/root zone temperature and EC levels in the grow media. Each sensor has a wifi transceiver. They have a Priva frow control system, so we will also develop the interface to get Priva to trigger watering s.

We are cost engineering this down to a point were you could put one on every plant and have seperate resovoirs per plant or group of plants. This will include a home version.


Hi Robogrow,
We have an existing solution developed and tested if interested. It is currently compat with the Fertigation Manager (ClimateControl.com)…and, of course, our own KnowYourGrow interface for logging/visualization/notifications. It is less cost than the GroSens, but still not cheap. However, you want robust and dependable if you are going to trigger irrigation. Each transmitter supports up to 3 sets of stainless probes (each with WC, EC, and temp). They are solar powered by sun or HID lighting (no LED). The enclosures are watertight and made of aluminum. Both soil and soilless mediums are supported.
Cost on 20 wireless transmitters (with 60 total sensors) and one receiver would be roughly 40k. You could grab the data from the receiver as it came in and make decisions on irrigation triggers. I have done the same with other systems and could assist as needed.
Shoot me an email if interested…
[email protected]


What does your system do with the data? The real need is to apply a diagnostic algorithm or better yet AI to adjust or flush to provide the plant what it wants. Or in some case deprive the plant to promote chemical production.



Please identify what your plants need and provide the water that is appropriate. Do not over water, and DO NOT under water. An automated system with proper filtration is paramount to plant growth. Use pressure compensating emitters and direct the water flow to the plant root system. PC emitters will allow for even water flow regardless of water source.,

Filtration allows for precise watering.

Ask for Antelco PC emission devices in order to assure yourself of the proper growth mechanism. You can insert fertigation as well.

Grow To Your Full Potential!!!


Guess that’s one way to do it. An alternative would be to ditch the expense needed by using flood and drain method, which results in salt buildup and necessitates flushing. Also, the transverse electromagnetic radiation from wifi transceivers is damaging to plant and human DNA.

A better approach (imho) would be to use a high flow nutrient delivery system which saturates the cube, eliminating salt buildup or moisture gradient. Also, with the proper cube selection for your genetics feeding is only required once per day with perfect root moisture during lights out - which only need be monitored once during initial system tuning or with new genetics.

Automation then becomes a matter of operating and monitoring the nutrient delivery system, detecting and preventing failures, and reullts in greatly reduced costs/complexity.

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IMHO you are wrong across the board. 1. saturating rockwool with high flow does let air get to roots. 2. Salt build up should occur if proper nutrient concentration is maintained. 3. Think about natural plant growth it rains soil gets wet then dries out. Plants are adaptable this is how they have evolved to response to changes in moisture. 4. At the end of grow, with optimal conditions plants consume cube water every 3 hours or so. If you only water once a day you will get much less production. 5. Water and nutrient consumption is not constant but increase over the grow cycle. (s0me water restriction is needed at end of grow to stimulate resin/TCH production). 6. In proper light loading, nutrient concentrations need to be reduced as a higher percentage of water get transpired for proper plant cooling. The best automation does not care what genetics are as it will “automatically” home in on the optimal feeding based on plant feed back. 7. Turn on a wifi every 10 minutes to report water content is thousands of time less radiation then your getting right now in front of your computer or the cell phone in your pocket.

The idea that human look at a plant and tell all that it needs is silly. Other than things like leaf curl, most plant responses are thing like IR emissions (chloroplast IR florescence and non chemical photosynthetic quenching) and stomatal closing/conductance. Even knowing when to remove fan leaves to preserve energy for flowers requires imaging and sensors that humans don’t possess.

Sorry to sound so harsh. But I tend to call them as I see them. If growers want the highest TCH yields they need to find themselves a real plant scientist and preferably one who also can enegineer proper automation. There are a lot of us out ther.

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We clearly come from different schools of thought. I’m not interested in replacing the Master Grower with a machine in order to make a buck, though MGs are in very short supply for the scale of this industry. That doesn’t make me a luddite, far from it as I’ve been building and programming hardware since the 80’s. I just appreciate real craftsmanship.

That said, I didn’t mention anything about THC content, terpine profiles or the like. That would be more dependent on genetics and nutrient solution than feeding style. Correct?

What I did say comes from exposure to facts and real world yields in excess of 3 lbs/light in rockwool with the method I described, and proven with customers who rapidly achieved profitability with very little automation. But, the ones that did so had a real MG who understand the plant and what it needs.

Personally, I don’t understand why setting up for nutrient lockout is a good thing (your point #2), please explain this as well as why you directly compare hydroponic media to soil, which have different dynamics (your point #3). Regardless of the media, if the roots get too dry the plant is done. No?

At any rate, I’m not selling anything as I’m moving back to technology and will be busy building an airplane. By hand.

Best of luck to you

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Sorry, #2 I meant “salt build up shouldn’t occur”

THC, other cannabinoids, terpenes, carotenoids production can be enhanced by certain stresses on the plant the cause genes to express and produce various proteins then the desire bio-active compounds. So restricting water, adding UV light, lowering temperature, topping, super cropping and other forms of training all increase the total production of the desired bio-active compounds. Master growers know these stressors. What they don’t know is exactly when and how much stress and inputs to give the plants to achieve desired results.

In my state Maryland cannabis is grown for medicine, being able to produce a consistent profile so dosing can be uniform is important it is not just about money.

My goal is to develop the best system for growing cannabis and other medicinal plants.

The average profit margin is about 25% in the industry, there is not much incentive to get better. In Colorado they are attempting to solve the dropping price of wholesale cannabis by applying economy of scale and the big guys are buying up the little guys. This will only go so far. As cannabis becomes a commodity like tobacco, this will change.

I consider myself a master craftsman as far as growing plants. If a craftsman can’t see that the fan leaves are reaching a point that they are taking more energy from the flowers then they are providing, he does know its time to remove them. He can guess at it or he can use my “jeweler’s loop” and view the plant in the non-visable IR spectrum to see the photosynthesis rate falling off days before the leave start turning yellow.

In my view many of those craftsman are brutes with sledgehammers trying to create the statute of David.

Here is n example of some of the research technology we are bringing to production cultivation of cannabis- Nebraska Plant Phenotyping: Nebraska Innovation Campus Greenhouse - YouTube

The ability to map genes and their expression to plant pheonotype will the future of the cannabis industry.

Measure yield by weight can be misleading because some growers will not precisely trim sugar leaf that is embedded in the bud.

The better the tools, they better the craftsmanship.

bud.ogv (4.86 MB)

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We can agree with each other on this, within limits as the tool does not make the craftsman. I’ve seen some amazing woodwork and blacksmithing, for example, with very basic tools. I’ve heard shitty guitars make amazing sounds in the right hands as well.

We seem to be cross-talking, as it were, as I find no quarrel with what you bring regarding phenotype, gene expression etc., where such technology may certainly bring great results. But, that’s not really the business end of an operation, though quite an important factor.

However, when a facility is not even hitting 2 PPL (double-ended bulbs), something is waaaayyy off. The last thing needed there is more technology. Not that you are saying such, but it is more common than you seem to think. I say, count yourself lucky to be limited to the high end of the market if so.

At any rate, what I find somewhat disheartening is an over-reliance on technology in many parts of the industry and an under-reliance on skill.

Given the shortage of MGs at the scale we are seeing, perhaps you will help address this issue which can only enhance the technology. That’s precisely what I was hoping for from this forum.

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I agree with you on a lot of these points. Maryland has 14 licensed growers who have had over a year to get into production. Dispensaries open on Dec 1 and ran out the next day. Something is way wrong in Maryland.


Hey guys some interesting views and perspectives in here for sure! I’ve got a little bit of a anecdotal story I wanted to share that I think kind of follows along where you guys have taken the conversation (I hope you don’t mind, I just see some common correlations.)

When I was a teen I worked at retail store at this tourist town in North Dakota. I had to learn how to hand count change back to customers which was pretty terrifying at first (you know, that darn math and all) but it didn’t take long really for me to figure out how easy it was to count back up (and fast,) and there was no BS’ing anyone on short change when you literally count it back to them. Now? I have kids just hand me a fistful of dollars and pennies and say “here you go.” The amount of times I’ve been given extra money back (or not enough?) Short change that till and someone might be getting fired. And these are the youth we’re preparing for the future (to maybe some day become master growers.) But we don’t teach kids how to count change back. Now a machine calculates it out, spits out your change (and they (the tender) still don’t count it back correctly.) At least with a fundamental understanding of how it works, they can better understand the technology that’s being used to replace those basic functions.

I emphasize education. We all need to get that understanding of the basics down (whatever it may be) and I don’t think anyone is not in agreement on that. If we’re identifying people don’t have those basics then let’s do something about it! Let’s build the better grower! Not enough MG’s today? What’s the forecast looking like for the future? That requires leadership, teachers, educators, planning. That requires some cooperation between the information and thought leaders. People come to the internet for their education on these kind of things anymore, I heavily see this coming from a home/hobbyist perspective side of the market.

I believe we as educators (and you are educators whether you consider yourselves that or not, I’m learning stuff from the both of you by these conversations so keep that in mind too when you’re replying wink wink!) but we have a responsibility to provide a nurturing place for that education, to develop those skills and have a better understanding how basic fundamentals can lead to a wonderful relationship with technology.

Technology can make our lives easier and put out a better product but it also can create dependencies that we may not have planned for. I’m approached by home growers all the time looking for a home automated system. Never grown a plant before, want the machine to do it for them. That’s probably not the best starting point to learn how to grow, but it’s a consumer market and people want the “easy button.” But the “easy button” is still a mechanical device that was engineered by someone and it was education that brought that ability to automate “easy.” I’m not here to deny anyone ease of access to growing, but I can help promote the education of what lead to “easy,” and that in turn I hope will provide a more prepared grower.

Anyway guys I just wanted to toss in my two cents, you’re both clearly passionate and it’s passion that drives our innovation (we just have to make sure we always understand we’re on the same team here from the education standpoint even with different views!)

Also, @Robogrow , would be interested in knowing the performance and solutions you come up with! Would you keep us posted? Also very interested in the home version (like I said, I’ve got a nice fit in with home growers in the autoflower market and many of these growers also grow photoperiod/full cycle; I’d be more than happy to discuss you with some possibilities of some performance testing done by home growers throughout the world (documented journals of the product in use, etc.) It’s a peer growing system with home growers, they rely on each other to know what works for products (I laughed as I wrote this last sentence, I think you’ll get where I’m going with this.)

I appreciate the audience, thanks!

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Jordan, Is your point that all new drivers should first learn to drive a manual transmission before they are allowed to drive a auto transmission vehicle? Or start growing non-auto flowering plants prior to grow autflowering plants?

I think SimLeaf is still free and does decent job of exposing new growers to the basics of growing simulated plants.

We are stiil a few weeks for the new nutrient controller prototype. Long lead times for the low cost valves from China.

We are shooting for a $299 retail price for a wifi controller with EC, water and air temp, humidity, pH sensors, 6 nutrient feed valves and one return pump . The pH circuit is now 1/10 the cost of the Atlas Scientific board we were currently using is 10 times more accurate. Since it runs on lower voltage the pH probes will last much longer.

Comparable systems start at $800 and run over $2K with pumps. http://growlink.com/shop/nutrient-controller/

We will be using the home controllers as distributed super computer to run genetic algorithms so that all growers will share the optimization of their grow conditions and plant inputs by strain to get the maximum TCH and profiles from their plants.

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I think everyone learns differently, comprehends differently, and all at different rates. Even if I were to make a case for learning manual over automatic first, that still requires someone to explain when to shift into gear, what’s happening internally when you grind gears, shift out of gear, etc. Will that make a better driver for the future? Not necessarily. Will it make a more prepared driver for the future? Ask someone who has only driven an automatic to drive your manual transmission sometime (usually a look of sheer terror on their face!) Explain a manual to someone who only drives an automatic -but- has also been driving for awhile (experience,) and now they are using preexisting knowledge to apply it to a common goal. So it can go both ways.

I’d like to think almost anyone can put a seed in the ground and grow a plant. The needs of a home/hobbyist grower are different than that of commercial facilities and vice versa (but there are some similarities and commonalities. Some people naturally grow well. Others struggle. Even with natural success or struggling, it’s education and information that bridges the gap for both of those types to gain understanding and ultimately leads to potentially better growers (or consumers, whatever the angle.)

To sum it up, educate. Educate. Educate! I’m an “ease of access” kind of guy, if people have access to the information and the information is solid, it’s up to them on how to process it (but also up to us on how to present it to them so it’s easier to process.) I won’t chew anyone out for skipping Chapter 1 on the book of “How To,” but I can make a case that if they didn’t read Chapter 1: The Fundamentals, Chapters 2-10 might seems a bit daunting and can slow down the desired result if they weren’t familiar to begin with. :smiley:

That’s great and a nice price point too! Checking out those links now! Any release date set on the home system? Have any pictures you can upload for us to see?

Appreciated Peter!

We can have different relationships with technology. Once one becomes dependent on the technology, what happens if the technology breaks down?

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I have been following this discussion with interest. Sensor controlled irrigation management in the forms of soil, nutrient, chemical or environmental is not new, however reliance on this as a primary form of irrigation management is somewhat dangerous. I was involved in controller and sensor development in the 1990’s and our findings were generally that these tools should be used as management decision support and not complete automation. The main reasons are that you are dealing with quite a degree of complex variables such as:

  • Soil/Water/Plant relationships
  • Nutrients
  • Water quality/treatment
  • Environment
  • Hydraulic considerations
  • Energy requirements
  • Scheduling/Timing Windows

In my opinion the better irrigation managers I have seen will use sensor inputs as tools and carefully manage irrigation scheduling based upon sensory and growing experience.

These comments above are generally related to open field irrigation and if you were using indoor methods where a lot of the parameters above are controlled then higher levels of automation can be achieved.


Not to beat a dead horse. Sorry Trigger. But I have to whole heartily disagree.

Cannabis unlike tomatoes require control of not just ideal environmental and plant inputs but various stressors to produce the desired profiles and bio-active compounds yields.

With thousands and now tens of thousands plant to ride herd on automation is a must. Paul Selena , chief scientist at Village Farms, (260 acres of greenhouses) has been my mentor for several years and has been striving for more and more automation in a market that provides very slim margins. Village Farms has hooked up with Emerald and is bringing 5 acres of cannabis online in Canada. He says conventional methods of water content measure doesn’t cut it with cannabis.

My point is no human can perceive plant responses in time to correct for them.

While I don’t recommend letting the robots and AI take the reins. I have been studying closely, for last 12 years, the efforts at Rutgers, Cornell, Arizona and other leading controlled environment research centers and found the controls are still rudimentary. There focus is still focused on traditional plans. Advances in high throughput pheonotyping is still focused on plants (ie. corn) in an attempt to avoid or re-mediate environmental stresses like drought, not to optimize these stresses for bio-active compound production (with the exception of premium wine grapes).

It is because there are so many variables that need to be managed that AI software is very much needed. I have taught NASA’s Valkery humanoid robot to walk, “see” and push buttons to open doors, etc. It would be very challenging for a human to control the robot in realtime to do these tasks. This is true with cannabis.

For instance cnnabis reaches it optimal growth at high temperature ranges, it sweats (transpires) profusely and a some point will close its stomata to stop losing water to the atmosphere. Noting heat stress in the plant a grow might dim the lights turn down the temperature. When the proper thing might be to reduce the nutrient concentration relative to the transpiration rate increase the CO2 . I go mater grower will take this approach but he has no idea exactly what the ideal concentration of nutrients should be as this is changing quickly nor exactly how much CO2 to pump in. Also, plants in a more stagnant air area need different inputs. My goal is to monitor each and every plant responding to each plants needs.

With a $1100 per plant cost for moisture sensors few growers can afford to do this. At $20 per plant it make sense.

Believe you are sign to the choir as the install base of “master grower” would hardily agree with you, but the industry will move past the current paradigm. Companies like Med Men with 8 grows and $100 million in walking around money went outside the industry and recruties Grower from EuroFresh the largest greenhouse tomato grower in North America.

Take a look at the automation that Hoewling tomatoes employees. From my view point even that is so yesterday tech.

I working towards where the industry will be in five or tens years not were it is today.

Thanks for indulging my mad scientistish rant.

Anyone need lser bud trimmer? https://drive.google.com/open?id=1iogGklTTyPJkxZ2Gz5JbkwIdWPUVJE7b

This prototype uses a $100 6 watt blue laser. With a $2K 20 watt surgical laser I can trim a 6 inch bud in a few seconds. And no it doesn’t catch fire in vaporises the leaf.


The problem with the academic mind, uninformed by practical matters, is that it inevitably leads us away from common sense if left unchecked.

There was an article recently about using satellite technology to determine the optimal watering for vineyards. I had to laugh when I thought about how that study would have valued that lovely, producing vineyard in Ukiah California which was dry-farmed (no irrigation whatsoever). The one whose owner grew up on a vineyard in Italy.

Do you really think that a $100,000 investment is practical (from the profit-making perspective) for monitoring 5,000 individual plants, especially when the irrigation system cannot adjust based on what is found? Do you have any idea how difficult it is to sell a $100,000 irrigation system that will put a grow in the black in week 5 of the first cycle to someone who’s been poisoned with the idea that it’s just irrigation - while they yield 1.8 PPL and go out of business a year later?

In my experience, the hardest obstacle to get over is our false ideas of ourselves and what (we think) we know.

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PPL is that pound per light? Pound of what THC?

Growers should be getting at least 2 lb per plant every 3 to 4 months. At $2K per plant that’s $30,000,000 a year. Why wouldn’t you spend $100K? Seems like a good investment to me.

I teach hydroponics for a land grant University, I doubt they would pay me if I didn’t “know”.


No one is getting 2 pounds out of a single rockwool cube, which is where your discussion started. Now you’re talking large soil pots with extended veg time?

Money cares about profit. Let’s start there. The product is sold by the pound of weight. THC/CBD content can affect the per/pound price, depending on the customer, as can the use of PGRs. Other factors, not all plant-related, are at play as well.

Perhaps we’ll talk about psyience vs science next!

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Hey guys let’s please keep the conversation civil. I’ve actually really enjoyed reading some of the back and forth on the science side of what you guys are debating here but from a casual observer standpoint, the brilliance kind of starts breaking down when there’s little “jabs” thrown in there to get the one-up at the end. You guys are brilliant, if that needs to be said by an outside party in this, let me say it. That said, it’s when we can keep conversation on point that we get to either a common ground or worst case, agree to disagree (prove me wrong but I think the latter is the winner in this one.) :smiley:

@JoeGrow , you raise some interesting points on automation vs traditional methods, why not create a discussion thread focused specifically on that topic for some friendly debate? Clearly it’s something that could be discussed further, but seems like it’s steering away from the intent of the original post.

Appreciated guys!

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