Hydroponic system nutrient sensors help

Question

Hi all, I'm going to be building a hydroponic system soon being controlled and monitored by a board (most likely beaglebone). But I need help with finding sensors and connecting them, I have literally no idea what connect tivity any boards have (rasberry pi, arduino, beaglebone/beagleboard, atmel) and if they're just USB, then finding a way to convert connections to usb. But I'll get into that later.

The sensors I need are:

Dissolved Oxygen

Hydrogen

Carbon

Nitrogen

Potassium

Phosphorus

Calcium

Magnesium

Sulfur

Boron

Chlorine

Copper

Iron

Molybdenum

Manganese

Zinc

Nickel

Sodium

Cobalt

Selenium

Silicon

Then PH and Flow rate sensors

Anyways, if anyone knows of any place to get these sensors please tell me or post a link. Also if they're not natively USB, explain a way (or post a link to an article) on how to convert the connection to usb.

Thanks to everyone that will help! This is my first project using any of the boards like beagle or arduino.

Also does anyone know of any pumps; both air and water; that can be run from one of the boards?

davewr · Answer

Just one more note -- if you consider the question answered - mark it as answered as a courtesy to me and to everyone reading the thread. If you have more questions start a new thread with specific questions or post them here as a follow-on to get the answers you need. If you have followed up on the links I gave you your questions should be quite specific now.

davewr · Answer

I suggest that you do a google search for the: Hach DR/890 Colorimeter It will give you an education into one way to test for chemicals in solution. It is widely used in industries (like mining and water quality) where people might want to test a solution for a mineral/element presence. Hach also have an HQd meter which you should look at. (Sodium, Dissolved Oxygeb (DO), pH, Chloide, Fluoride, Nitarate, Ammonium. Genrally when testing for elements in solution you will have to mix solutions and look for color changes. In any case other people have done the work and provided an economical solution. I don't think that you require real-time monitoring.

xan326 · Answer

Will those work for continuous testing? I'm looking for something that will monitor the levels of the minerals and nonmineral elements for an extended period of time. But thanks for the start! And I do require real-time monitoring as I'm looking for something that will give me results when I need them. Incase you are unaware a hydroponic system is used to grow plants, so I require monitoring all times, as opposed to doing small tests frequently. I find that having a system that can monitor at real-time all the time (and yes of course I will need to re-callibrate the monitoring system)

davewr · Answer

I am quite aware of what hydroponic systems do and are. What you are asking for does not likely exist except for specialized tests. If you look at the materials and read the data sets (in pdfs on the Hach site) for the reagant packs you will understand better what the issues are. Part of my work as the science officer for a mineral exploration company is to hunt down this type of instrumentation and determine what is most likely to be useful in "field" operations and use by unskilled people. Unskilled in this particular area as they often have an MSc or PhD in geology -- though some have little education. Now, if you want to invest large amounts of capital I can point you to companies that could no doubt design you a real time system -- but they would likely be based on the same techniques as in the hand-held hach and/or the DR 5000 photospectrometer from Hach. http://www.hach.com/dr-5000-uv-vis-spectrophotometer/product?id=7640447361 Some meters like pH meters and TDS meters probably can be implemented in real time -- but does the conductivity measure result from Copper, Silver, Aluminum or manganese? You tell me. You need to go back to your basic chemistry and study of minerals to see why these tests work and why they are used. I doubt very much that you need real time measurments of trace elements in any hydropnics systems. Maybe Nitrogen based compounds and pH -- but why the others? What would be the benefit? PS: I have designed heap leaching (Thisosulfate and Cyanide systems) and designed and built the electrowinning systems for plating out sliver, copper and gold -- so I do know a little bit about these systems. However, a little knowledge is a dangerous thing -- so I suggest you start digging for further information by starting with test systems that actually work -- and go from there. (So I am guessing less than you might think -- that plus studying agriulture for four years and computer engineering for four years -- so I have some relevant education to back up my opinion as well.) My point is not that I know a lot -- but that that I consider myself a rank beginner at this -- but apparently I know a bit more than you. Start digging! Basic R&D and investigaton should come before you specify the methodology.

davewr · Answer

I think you will find that most "automated systems" measure only pH, TDS, and EC -- perhaps temperature and humidity. Much like I said. I suggested that you look at how the analysis systems work so that you can see what the issues are. Do that. In the meantime -- if you have the bucks photospectrometers start at $9000 -- maybe you should consider one per element. When you supply a budget figure maybe people can be of more assistance. See here: http://www.appliedspectrometry.com/pubpdfs/4-On-Line_Spectroscopic_Monitoring_of_Plant_Nutrients.pdf and here: http://peterphrastus.com/drupal/ And here: http://www4.agr.gc.ca/abstract-resume/abstract-resume.htm?lang=eng&id=27755000000662 But surely you can use google too! Best wishes. This might be useful as well: http://www.reeis.usda.gov/web/crisprojectpages/0213548-optical-fiber-sensor-for-plant-nutrients.html Non Technical Summary Nutrient concentrations in greenhouse crops have a direct effect on the yield and quality of flowering plants. Nutrients are often applied on a rule of thumb basis and the level of nutrients and salinity "in the bag" is controlled by leaching with the salinity level measured with a salinity sensor in the leachate water. However, specific nutrient measurement is expensive and often requires wet chemistry. Two different approaches have been used so far: Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) and Ion Selective Electrodes (ISE). The ICP method is very sensitive and selective however, it is also expensive: on the order of tens of thousands of dollars. The ISE method is portable and cost effective but suffers from interference from other species, is subjected to electromagnetic interference and requires constant maintenance. It is the purpose of this project to develop a unique, low cost multi point/multi parameter optical fiber sensor to monitor the primary nutrients (nitrate, phosphate and potassium ions), in hydroponics solution. This is a real time single strand optical fiber that has an active cladding sensitive to the targeted species.

davewr · Answer

As I said: I think you will find that most "automated systems" measure only pH, TDS (Total Dissolved Solids), and EC (Electrical Conductivity). Monitoring TDS of your water supply vs what is in the tanks should give you an indication of nutrients available -- i.e. a proxy . You can also measure temperature -- air and fluid as well as humidity -- all important factors. From that data you can control the HVAC (Heating, ventilation, air Conditioning) -- more important than close momitoring of trace elements. So whether you are growing "recreational crops" or tomatoes you can establish some controls. Most of the trace elements can be checked on a much longer time span -- whether it is once a week or a few times a day should not really matter. If you dump in too much iron -- you will get a pH shift (more acidic). So some things can act as proxies. My suggestion is to get something like the Hach DR/890 and measure the elements on a regular basis -- but every few days -- or if you spot trouble. As those research papers point out easy measurement of the trace elements may appear "soon". You can automate the constant measuring of the other elements -- but you will need mechanical systems to sample , flush and clean the measuring equipment. Not simple and not cheap! You can also measure CO2 -- the more CO2 (to a point -- say 2% max) you will get beneifts for plant growth. See here : http://www.co2science.org/index.php Useful articles there. Oxygen sensing is expensive -- and likely not needed. You could also measure and control hours of light and darkness. All useful in some ways. If you have a million dollar budget -- contact me -- I'll help you spend it. If you have a $200 budget -- do what you can do most easily of what is most important -- pH and CO2 in my mind...

davewr · Answer

I will also point out that browsing through one of the Newark (newark.com) sites will help you track down sensors, Most sensors are analog (ADC) or TWI or SPI interface -- some of the humidity sensosr expect you to be able to pulse count -- measure freqncy of an oscillator. Generally, most TWI sensors and SPI based sensors have a lot of intelleigence on board and will feed you back numbers as answers -- then it is up to you to translate. Many have "drivers" you can find on the internet and adapt to your use. Go to the Newark site and look for Sensors or find the specialized sensor section. It might make more sense now.

dlmz06 · Answer

I used to grow hydroponic vegetables. Really, tomatoes, basil. The easy way is to buy a commercial premix two part fertilizer solution. This is added to the circulating water in the hydroponic system until the solution is the right concentration. The electronics then only needs to monitor the dilution using a total disolved solids meter. Small digital handheld disolved solids TDS measurment "pens" costs about $30-45. If you keep the water level constant the plants use the fertilizer and you add more as needed to maintain the disolved solids. Maybe one of the inexpensive pens could be modified to interface with your CPU, or maybe there are more expensive commercial TDSwith digital outputs The commercial liquid two part mixes come comercially balanced and measured so you don't have too make all the measurements you describe. There are solutions balanced for bloom or vegetative growth. If you worry about the other elements, just flush and reapply the desired analysis fertilizer, unless you need to be a research lab wtih all the equipment and sensors. The premix fertilizer is cheap and a little lasts a long long time.

Former Member · Answer

I have a lot of experience in Hydroponics, I have designed hydroponic solutions from the ground up and done testing on them. Daniel is right you dont need to monitor everything you have listed. You have listed all the major components was well as all the micro-nutrients needed to maintain the plants. All you have to do is monitor the PH and TDS in solution and simply flush and re-new as needed.

However, if you are trying to monitor an experiment and determine the uptake of given nutrients within solution so you can simply add back what was removed. You are looking for a spectrophotometer which you would need to make and interface to any of the micro-controllers. You would use it to do Absorption spectroscopy on the solution. Samples could be diverted from the main flow line into a secondary line for testing then released back into the main flow line after the test. Most spectrophotometers use a cuvette for sample preparation. These tend to be plastic but in the case of UV spectroscopy they are quartz. You would have to look up each of the chemicals you list and determine what spectrum they absorb. You would also need to make sure that the sample test area is made of a material that will not absorb the spectrum you are trying to identify. If any of them are in the UV spectrum then you will need to use quartz at the sample point and the design gets much more complicated.

None of this is easy or simple, I would suggest that you stick to the standard PH/TDS tests unless you are up for a challenge.

Problemchild · Answer

I must agree with what David says here. The sensors are similar for Ponds/Hydroponics/Aquaponics etc.

If you want to test for a specific compound or ion you need to do the chemical test for it using the reagents as David stated. Most are designed then to change colours for a colour sensor to pick up. The tests can be automated using some kind of dosing kit to introduce an amount of reagent into a test vessel.

Probably more useful is to use the sensors that measure directly for dissolved O2, pH,TDS etc(I believe the NH3 sensor is reasonable too). All these are quite expensive (in the 10's-100's) depending on the particular sensor and how scientific you want to be.

Good luck with your project ... John A

kidiccurus · Answer

Seems no one has talked about actually interfacing the sensors with USB so I will try and cover that here. All of the boards you have described can use gpio pins to read sensors, often through i2c. Converting a sensor to usb is not generally desirable unless the final device is a usb connected sensor. Personal recommendation is arduino. It can interface with most things. It can also read analogue values which if often helpful for cheaper sensors. The only reason to use beaglebone or pi is if you want a computer interface or web connectivity, otherwise arduino is cheaper. You also get more gpio per pound (or dollar or euro or yen) with arduino. When you find your sensor I can help you use it correctly.

Problemchild · Answer

I must say that we've looked in to this before for a friend and found in practice you do not need to measure continuously nothing happens that fast although you do need to keep a regimen of just how often and running around a small out fit with a TDS truncheon generally isnt often enough.

I think the problem is that if you are making it operate automatically and on a small scale you will find it awkward to dip in say a PH or TDS meter yet they do get contaminated overtime so you cant really leave them in solution. The indirect method via colour change reagents gets past this at the expense of requiring some dosing equipment and way of extracting a sample.. all very awkward to do reliably for a cheap price!

michael.webb@csiro.au · Answer

Hi Xander,

You may want to look at the following reference:

Webb MJ (1993) A multichannel pH controller for solution culture systems. Plant and Soil, 155/156: 501-504.

It describes a multichannel system for monitoring and adjusting pH in six separate hydroponics systems, hourly. The Orion meter had seven channels which could be switched using a command from a computer. You will note the date, 1993, so yes old technology by today's standard (eg RS232 communications !); but the principles are the same.

Equally, this Orion system could be connected to different ion-selective electrodes and an electrical conductivity probe inserted into one hydroponics system. It has been a while since I have been involved with hydroponics, but apart from pH (which is a hydrogen ion selective electrode), I think there have been developments in other ion-selective electrode ( eg Ca2+, K+, NO3-, NH4+ ) . Note that these measure nutrient in there ionic form, So nitrogen is measured as both nitrate and ammonium ions, Phosphorus, if a probe exists, would be measured as phosphate (the form and valency will depend on the pH); but this doesn't matter as it is the ionic form that is taken up by plant roots.

Note that pH affects the uptake of phosphate (see Webb MJ and Loneragan JF (1985). The importance of environmental pH during root development on phosphate absorption. Plant Physiol., 79: 143-8.)

I am not aware of any probes for the micronutrients; but as other have mention, you generally will not need to worry too much about these between solution changes. However, it is possible to control the 'activity' of the metal micronutrients such that the activity is near-constant. It is the 'activity' that the plant roots 'see' rather than the concentration (see Webb MJ, Norvell WA, Welch RM, Graham RD (1993). Using a chelate-buffered nutrient solution to establish the critical solution activity of Mn2+ required by barley (Hordeum vulgare L.). Plant Soil, 153:195-205).

You will need to be careful with boron as the range between deficiency and toxicity is quite narrow.

If the solution is constantly aerated, you will not need to monitor O2, and CO2 will be purged.

I hope this helps.

Cheers

Mike

nightparrot · Answer

I know this is several years old but found this today Libelium Smart Water Sensor Platform Adds Ion Monitoring

Not sure the price but probably several hundred $s.

And if you search thru their pages they have something about the lowran and connecting via Pi, beagle, etc

Place to buy the board and probes: https://www.cooking-hacks.com/smart-water-ions-sensor-board

smanand · Answer

Dear All,

Im new to aquaponics, hydroponics. i understand the content in the water is critical for both.

Thanks to Xander Zoolander, i was thinking of the same problem ,

I also acknowledge other experts in the field who says real time monitoring is not required.

Having said that, i would appreciate experts comments on my view(im probably, over excited and optimistic that there is a way out)

The reason i believe a real time monitoring will help

1. Measure the effect of feeding fish, will help me know quantity and interval of the feed. ex. after feeding the fish , in the next few hours if i know the quality of water. i would know how much minerals in the water, will help me do course correction on day 1. i believe this will help me save time.

2. effect of environment on the quality of water.

3. know when to take action instead of waiting for an 'event' to occur.

4. Will help me decide if i have to increase or decrease the no of fish or plants. currently i have a ballpark figure, which may not be real for my environment.

currently, these are learned over time by trial and error. takes months to get it perfect.

my objective is not to have an automated system but to have total control of the system.

I also checked Libelium Smart Water Sensor, how reliable it is? does it solve the problem?.. im not looking at the price at this moment.

Would appreciate any feedback.

Thank in advance

anand

Hydroponic system nutrient sensors help

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