A few pics:
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Nice!
I wish I had your programming skills.
I especially love your enclosure! I am a big fan of Tupperware enclosures for DIY electronics projects and other things! 
Early version siphon tank and manifold. Ive also used similar enclosures for specialized battery chargers, and other projects over the years.
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Yey! It works! Turns ON/OFF by pressure plus maximum ON time / minimum OFF time, like starts at 250 kPa and then works max 5 minutes and then should rest for at least 5 minutes.
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Seems that I’ve been able to increase compressor start interval from ~16 minutes to ~53 minutes which is pretty good result I believe.
At the same time I’ve made some new - more precise - measurements. I’ve marked them with bright green (lime?) color in the spreadsheet.
I’ve also made a long-run test, I left the system work for the night, like 10.5 hours. Towel test made a paper towel somewhere between “dump” and “wet”. Going to clean some mess I’ve made around over the last few weeks and mount the lights.
Now I’m trying to figure out what to do with nutrients. I have a few formulas but totally forgot all chemistry I had in school so wondering how to make the mix out of available fertilizers.
Is “Making your own solution - Getting started” tutorial available? 
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Excellent!!
Ah - so this is to help with the regulators bleeding air so much? Thats quite an improvement.
I still cant understand why anyone would make a regulator that works that way. None of mine have ever worked like that. Good thing too, because I could never make a switch like that 
Interesting. I would have expected the towel to be soaking wet after that long. Towels dont drink any water like roots would, so it should have continued to soak up water the entire time. I would have expected the towel to holding quite a bit of water. Makes me wonder if you might be running on the dry side? It could also be that the very top of the chamber isnt getting enough mist?
Viewing a laser light from the side might show if thats the case.
Just dont use anything that has any organic ingredients. Im talking about anything that comes from a plant base or things like worm castings etc.
I really like the three part Jacks Hydro mix, but I have no clue if strawberries would like it as much. The Miracle Grow stuff is similar to Jacks and is used on vegies and fruits, so either should be fine. The General Hydroponics line is also good, but much more $$$.
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Actually it seems that they don’t bleed that much. I’ve tried to measure bleeding with a new pressure controller and it is shows like only 0.02 \ 0.04 l/min (depending on pressure).
But anyway, now I can make the compressor to turn on at 2-2.5 bar - this is the main reason the interval has increased that much.
The idea behind of this pressure controller is:
- To have more precise pressure control (which isn’t reached as these sensors aren’t precise enough, especially on low pressures).
- To be able to control compressor via pressure and time settings
- To be able to control power socket(s) and conveniently set ON\OFF schedule (for example, for the lights schedule).
- Later to be able to automatically keep real schedule and pressure settings and then somehow to manipulate with this data: make analysis and so on.
I would better go with the main controller but these sensors are analog ones and Raspberry PI which I use as a main controller has only digital input pins.
I thought to make my own solution out of the raw mineral fertilizers. The problem is that they are mostly salts (like CaNO3) or simple mix like N: 13.6%, K20: 46% or even complex mix:
but formulas I’ve found look more like: NO3: 141, NH4: 14, P: 47, K: 220, Mg: 24, Ca: 130. So I need to calculate how to make a proper mix out of available fertilizers.
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Here is a laser pointer test video:
Air 0.6 bar, 0.45 bar water, 0.5 s ON, 14.53 s OFF, laser pointer test
No sound unfortunately 
And two videos of Air 1 bar, water 1 bar, 0.5 s ON, 22.31 OFF
Top down:
Laser pointer:
Seems that mist evenly fills all the chamber in both cases. The second case should produce bigger droplets. Don’t know what is better though.
Misting stopped in a few minutes before the end on all videos to check hanging times. On the first one misting stopped at around 13 minutes I think (not sure for 100%).
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Lovely work.
On fertilizers, I’d suggest starting with Jack’s Hydro or something similar (no organics). They also have a micro-nutrients mix. Once you get things dialed in, start playing with mixing up your own formulation. It’s a lot of work to mix it up and, for that matter, to get the ratios correct. And, there are certain complexities such as buffering that can be difficult to get the right combination of salts.
Once you have something that’s known to work in your system, you’ll have something to compare to. Then try mixing your own formulation. It might be difficult to determine the source of any problem that occurs, otherwise.
I think this is a great idea but I’d opt to get through a successful grow cycle on your new system, first. Just a thought.
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Thats not too bad at all. Far better than what I thought they were leaking.
That is excellent! Very few pressure switches allow that much range of adjustment. Mine only allows me to go down to around 4 bar.
I have no experience with that, so cant help.
Interesting.
Im too stoned to figure out your spread sheet at the moment, so Im have to ask questions
Remind me - chamber volume and how many ML are you putting into the chamber on each cycle? Im trying to gauge your flow rate to mine and how “full” you are getting the chamber on each cycle.
Im concerned on two points - the mist that fills your chamber seems to take a long time to build up. That suggests that that is mainly composed of the smallest droplets - the ones that can stay suspended for several minutes. I would guess 20micron or less. Probably smaller than that.
Your laser beam also seems very dim compared to mine. You can see when a pocket of mist enters and it lights up brightly, but that condition doesnt last long at all. At least compared to my setup.
You are using very short ON and OFF times compared to me too. Im currently running 1.6 sec ON and right at 60 sec OFF. At 1.6 sec ON, my flow rate is .058 ml/gallon/cycle. That works out to .083 liters/day/gallon. My chamber is aprox 55 gallon.
Those numbers are on the hi side of Atomizers recommendations, but my roots have never been happy at the lowest numbers he recommends. The mist is too thin and the roots just grow sideways with lots of air pruning in areas that dont get good coverage. I always have to start the new babies at rates higher than he recommends and slowly come down from there as they get adjusted to the system.
What that adds up to is - I think you may be running on the dry side. The only way to tell for sure is to put some plants in there and see what the roots tell you. I may be completely wrong 
Oh - I also noticed some light leaks around the top of your chamber. You will want to block those off as roots dont like light. Its also possible you have air leaks at those same places around the top. That could easily be lowering your hang times. You want a very well sealed chamber. Not 100% sealed though. There needs to be a way for the air you are blowing into the chamber to escape without blowing your plants out the top. I suspect your pots will allow plenty of air to escape without blowing the plants out too.
How soon do you plant to start torturing some baby plants? 
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Thanks for the advice, guys!
I have some formulas dedicated for strawberry and thought to periodically do plants analysis (leafs and petioles) to compare reality with reference data.
The problem with existing mixes is that I can’t find anything close to what I need. For ex., one of the formulas is above, an another one - more detailed - is like this:
6 meq K+, 7 meq Ca2+, 6 meq Mg2+, 1 meq H+, 12 meq NO3-, 1.5 meq H2PO4-, 6.5 meq SO4-, with the following concentrations of micronutrients: 3 mg L-1 Fe2+, 0.5 mg L-1 Mn, 0.1 mg L-1 Cu, 0.1 mg L-1 Zn, 0.1 mg L-1 B
Which is in mg/L: 234,588 K, 140,273 Ca, 72,915 Mg, - H+, 168,083 N, 46,460 P, 104,203 S, with the following concentrations of micronutrients: 3 mg L-1 Fe2+, 0.5 mg L-1 Mn, 0.1 mg L-1 Cu, 0.1 mg L-1 Zn, 0.1 mg L-1 B.
K:Mg balance is pretty important and should be like 4:1 . Micronutrients are also pretty specific to strawberry.
None of the available mixes offers anything like that.
Do you think it is better to go with non-optimal but factory-mixed solutions?
My chamber volume is roughly 420L. I’ve got Atomizer’s MIN/MAX numbers: 1.3 to 2.6 liters per 100L per day (from 5.46 to 10.92 L per day for the chamber). I’m using the lowest value as of yet, so with 1 bar water pressure my flow rate is 1,64 ml per cycle (0.5 sec ON, 23,37 OFF) dirty or 1,5085 ml per cycle without overhead (~0,0136 ml/gal). With overhead it gives me ~6 L of water per day for my volume.
Why? I would assume the particles rather big and have difficulties to climb up… 20 micron particles would easily go up with all that pressure and hang closer to 2-3 minutes, don’t they? 
I think this happens because particles are pretty big and falling down quickly so nothing to reflect of - which in turn makes the beam look dimmer. Like at the beginning: empty chamber, no visible light beam at all, just bright dot on the floor. Then after some time mist starts to fill the chamber and beam become more and more visible. This is actually tells that particles might be closer to the expected size (0.05 mm) but is that a “correct” size - don’t know.
It is pretty important that camera is in an around a 100 cm from the laser pointer and right next to the one of the nozzles.
It might be but these holes are pretty small. They look bigger than they are and this is actually the only wholes except the tap hole. I’m still thinking about them: foam plants holders sit pretty tight so there will no any gaps around them or around a plant. I don’t want to completely seal the chamber. So I either need to make some other holes or leave these as they are
A perfect question! I hope my seedlings still alive in a fridge. They are there for 2.5 months already. But look green, so I hope they are alive.
Actually I’m going to figure out what to do with nutrients solution and try to put one or two plants into the system. I have 30 seedlings IIRC but don’t want to start with all of them at once
By the way, speaking of nutrition. I have a solution calculator:
It is in Russian, but in overall: it has a small fertilizers database with their composition including oxides (and I can add new ones) which I can use to add different fertilizers into a scheme, set weights and calculate resulting composition in raw elements like K, P, Mg and so on.
And I think is it ok to just mix everything up? Would there be any additional reactions between components?
UPD: On second thought I believe that it is ok just to mix everything up. The bigger formula is from a hydroponic-based research, so if they’ve used that composition they inevitably mixed everything together into a solid solution. So I’m going to buy components and see what would happened 
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By the way, I have a question according to the nutrient solution. I need to put there some micronutrients and the only way to get them is use chelates, like zinc chelate or copper chelate. Any chelate is an organic-metal molecular entity, so it has “organic” in there. I assume that as it requires very little amount of these (like 0.5 g in overall for 20 liters) it is safe to use it but am I correct with my assumption?
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Hey guys, great thread here, have a few things if I can remember everything to post about.
@heathen I think you mentioned trying different solenoid positions but sometimes they are supposed to be vertical/above the line and not sideways which correct me if I’m wrong, but it looks like yours might be sideways. I wonder if that’s contributing to your squirt of water every time.
A couple other things I’m also curious about:
If a 10ish micron size might be best for two reasons, one it falls within that 5-50 range, and two, while not the most extreme, it allows for really great hang times which would be of great benefit efficiency wise allowing for possible longer off times. Maybe the smaller size will allow better dense root penetration when chamber is full/saturated.
And this leads me to another interesting thought/idea… from what I thought I read about the NASA experiments, it needed pressure to reach inside of dense roots…
Well, I know you guys interpreted that as them having to spray the roots because of gravity, or lack there of, however, what if what they meant was that the chamber actually needed to be pressurized a lil?
I know you guys have been saying not too have a pressurized chamber because it would blow plants off, net pots off, collars off etc… but what if you could try to tackle those issues and actually pressurize?
Would that force the water/nutrients/O2 into all the roots more, including inside dense root balls?
Just a guess, but I would shoot for some chamber psi very small at first, maybe like <1psi (sorry I don’t have a sense of bar) just in case it would instead harm the roots…
Also, I think it would be interesting to discuss about what if any organics could be added to solution like Yucca and others or why that might be an issue? I have heard some growers have had success with hybrid synthetic/organic mixes but I don’t know much about them and I don’t know if they were aero, whether or not that makes a difference.
I too have bought individual specific minerals thinking I could diy, but I like as someone mentioned above that it’s prob best to start with a retail product like Jacks or something till you get your system dialed in.
And one more thing I’m a lil uncertain about, should nutrient res be aerated to keep longer or will it still keep the same amount of time and it’s unnecessary because it will get dissolved O2 when it’s atomized?
PS anyone running Jacks three part, you can get basically the same part B cal nitrate for like half the price here:
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Organics have been a difficult problem, once Larry drops back in he can describe some of the issues he’d discovered. Was interesting…
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Hmm, I guess I must have missed that somewhere as well as I’m sure some other things.
Hi! Thanks for posting!
Exactly the same thing happened with other solenoid type as well. It might be, of course, solenoid issue, but these solenoids are pneumatic heavy-duty train ones with pretty much force. I believe I’ve positioned them correctly because if I put them otherwise (other flow direction) they are starting to sip (at least, if IIRC, it was some time ago). But it might worth a try, but later, not a big deal as of now. My measurements show that there is only 8-10% overhead in comparison with continuous misting even on a long run.
Here is one of the discussions about droplets size, Rasmus Bjerngaard’s answer is particularly interesting. And he offers a link to the review of the NASA research. I’ve requested a full pdf from the ResearchGate, but there is a copy on AeroponicDIY available. It is an extremely interesting article, I believe I’ve read it but no carefully enough.
10 microns is way too low I think. Less size - more surface tension, so probably they are going to just bounce and don’t stick to the roots. Less size - less water inside: sphere volume is 3/4 * pi * r^3, so, for example, 20 microns and 10 microns particles volume differ for 8 times. At the same time surface area difference is just 4 times. So they are going to evaporate too fast and get a very concentrated solution at the end which is not good (and they are getting even smaller at during evaporation).
But of course all of these are speculations.
Pressure doesn’t do anything by itself, only the pressure force direction. Pressure in fluids and gases are the same in all directions. So I can’t imagine what would it change in macro particles behavior. In micro - like atoms - it would make them more dense, so they would collide more and make temperature higher as a result - in a short term.
Not talking about technical problems of getting the chamber under pressure: we have at least one inevitable hole - water need to be taken out somehow. So I would like to see a more or less solid scientific basis on that to make a try. Could you offer any explanations why would it work and how?
The problem isn’t that roots don’t uptake nutrients, the problem is getting enough particle size to make it impinge and stay at the root surface and not merging them into thick water film at the same time. At least as I see it and I can be wrong.
Any organics is good environment for microogranisms, bacterium. It is possible to eliminate them with ozone treatment I believe but still need additional complexity. But I also read that organic mixes might improve nutrients uptakes.
I think it has no sense to aerate with aeroponics, especially with AAA cause with every cycle you inject a lot of additional air. Also the paper above states that misted environment getting roots to take more oxygen than in comparison with deep water or no-mist cases.
Well as far as the pressure aspect goes, no I don’t have any science behind it lol but I just figured that the root may possibly maintain a regular atmospheric pressure and if there was a higher pressure around/outside of them, naturally it wants to equalize and press into all of them, hopefully with the saturated wet fog as well… I really don’t know what I’m talking about though, just throwing it out there, could easily be nonsense lol
As far as securing the drain hole, you could put a low pressure release/relief valve and then a larger diameter pipe around that to drain whatever that releases.
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I’ve got an idea on how to simulate roots. I don’t have thin enough fishing line or something like that (I’ve seen ones like 0.025 millimeter), but I’ve got a paint brush, cut hair and glue them on a stick.
Then I put it to one of the foam inserts and installed lid to the chamber.
Just to test I’ve put the system on 1 bar air and 1 bar water with both nozzles ON for 0.8 sec and 75.58 OFF schedule. After around an hour and 20 minutes it looked like that:
Edit: I put a picture to the next post to allow zoom it.
I don’t have a macro-lens but even with normal ones it looks exactly as I think it should. May be even more as I don’t think there should be big drops. It is also interesting that the stick itself as well as cover doesn’t feel wet.
Now I’m going to dry it a little (it is 31 Celsius at the moment so it is going to dry pretty fast) and run with my previous schedule: 0.5 ON x 23+ OFF and split nozzles.
By the way, I’ve also got all fertilizers I need, just brought them home from a pickup location.
I hope I’ll start with plants tomorrow or a day later. Very exciting.