HP Aeroponics exact spray without tank


#1

What do you say about this solution for HP Aeroponics spray system.
1 Activate Direct Drive Solenoid Valve
2 Start HP diaphragm pump (~4l/min ~0.7MPa). The nutrition flows back into the reservoir, pressure in pipe is to low for antidrip nozzle.
3 Deactivate DDSV for 1 second. Preasure rise in a moment and nozzle uniformly sprays for 1 second
4 Stop pump

Pipe OD 1/4" or 3/8"
One of the advantage of these system is, that you can detect clogging by measuring pump current consumption and (or) pressure during spraying.
The water in the pipes can be replaced with cold from the tank before spraying.
You can change nutrition in few second, without interrupting the system.

We need 2 branches because DDSV have oriffice only 2.5mm and douring open stage pressure at anti drop nozzle must be low enough that there is no spraying.
I’m waiting for these and these DDSV
For pressure regulation, pump could be powered at lower voltage via these DC DC converter, which also limit starting current and increase pump lifetime. Converter can be connected to 12V accu, which have 13.7V when it’s full


Building aeroponic system and full automation
#2

Very clever…took me a while to digest this method. Seems like it is worth testing.

I appreciate the benefit of flushing the mist line as my current approach uses an anti-drip drain head which runs counter to my auto-drain valve (opens < 15 PSI). https://smile.amazon.com/gp/product/B0044FWBZY

In practice, it flushes the mist line when the pressure drops from gravity as it is located at the bottom of my mist wand rig. The remaining nutes get pumped out with the mist that collected at the bottom of the Grow Chamber.

When the pump cycles on it takes 1-2 seconds to build during which time the auto-drain valve drips nutes but then it closes, the pressure rises dramatically, and the mist heads activate at about 60 PSI…the pressure needs to get to 100 PSI for a nice airborne mist.

With your approach, the mist line regularly is flushed back into the reservoir. I would not need the auto-drain valve but run a line back to the reservoir. That line would need a solenoid which I could control from my Arduino directly or with a relay (depending on voltage).

What I don’t understand is the voltage comments and regulator. Can you elaborate on the purpose? You mentioned a benefit for pump lonegvity but I do not understand.

Thanks,

Dominic


#3

If we lower the voltage, the flow and pressure will decrease, so the pressure can be controlled by the voltage.
The DC motor has a very high start-up current and thus a torque and noise, which undoubtedly results in a shortening of motor life, possibly also a power supply, at least you don’t need so powerful supply.
We need to know that in the blocked state (the pump stops) or at startup, the set limit current, like 4A, will flow into the pump, the voltage on the pump will be ~3V, and only 1A will flow into the DC/DC converter. With direct connection to power, we get about 15A peak current consumtion.
By limiting the current we get a soft start, and also limit the maximum pressure, for example, if the pressure switch breaks down. These could work for short time, because pump will heatit up quickly, which is not the problem because we run pump for few second only.


#4

I’m interested to hear what @wsnook @Jlniemi @Atom think about this.

It’s an interesting idea. Correct me if I’m wrong @Tehnicni but this will consume more energy than traditional HPA due to the pump being on longer.


#5

When pump run with free flow (0.3bar) it consume only about 1.5A and these is only maybe 1/2 sec, which mean 0.6Wh per day and 0.2kWh per year.

PS: If anyone would be interested in my spectrometer & LED DIY results COB LED Lighting


#6

The issues i see are that the pump will still be cycling hundreds of times a day compared to once or twice a day (or week) for an accumulator equipped system. The option of running drain to waste isnt viable due to the nutrient used during the pump run up phase. The DDSV will need to be activated again at the end of each cycle to depressurise the lines or there will be a lot of run on until the pressure drops to the ADV cut off pressure. The amount of nutrient being recirculated unnecessarily from the pump soft start phase and pressure dump will provide greater opportunity for pathogens etc to take advantage compared to it remaining in the reservoir. In my experience, the benefits provided by an accumulator equipped hpa far outweigh the initial outlay. If a pump has to be replaced several times during the lifetime of the system, the cheaper option will become the more expensive option :wink:


#7

is greater, but how much?

Ofcourse, I wrote DDSW must be closed for 1s.

Did anybody know what is the main reson for pump defect. I thing running at high presure. For >5 bar at the nozzle all the time, pump must fill tank with let say 7 bar. And which type of defect is more often?

By the way, how strong LED lighting / sq ft we need to grow lettuce? Do we need more power because the plants grows faster? For planting seedlings I plan 10W / sq ft


#8

If you run 1 second every 5 minutes, your pump will be cycling 2037 times per week, the DDSV twice as many. My pump charges a 100L accumulator in less than 10 minutes and the accumulator will run a system on that charge for at least 2 days. In terms of cycles, it would take my pump over 11 years to complete a weeks worth of yours. I would recommend getting the system up and running as thats the only way of testing theory :wink:
Ive added pumps, accumulators and chambers over the years but ive never had to replace a pump. The last electric pump i bought was last year along with a 25L accumulator. Several years before that i bought a rothenburger rp50 manual hydrostatic test pump. it delivers 45ml per stroke at any pressure upto 725psi. It can pressure test system plumbing / accumulators etc. It can also be used to charge accumulators with nutrients without the need for any electricity, just elbow power :wink: It couldnt be used as a standalone pump because you`d have to stand next to it day and night.


#9

I would use dosatron and pneumatic pumps
i plan on doing this to get rid of holding tanks
Also one could change their nutrients on the fly with this set up- much like a i.v for plants.


#10

These mean running pump for 2100 s per week in comparrison with mine less then 3000. With soft start I thing that number of cicle is not the problem.


#11

You wont know until you have it running, theory doesnt always work in practice :wink: I would email the manufacturer or supplier of the pump to ask their opinion, id make it a hypothetical question just in case it adversely affects your pump warranty ;) I can say there are far more forum posts involving pump failure in pump only hpa systems than in accumulator equipped systems if thats anything to go by. It may be coincidence but the same can be said for cycle timers (especially DNE branded) running pump only systems. Im not optimistic you will be able to pressurise your entire system from 0psi to eg100psi in the 1 second window, especially if you have several feet of tubing between the pump and the ring manifolds etc. Pulsation may be a factor here as its prevalent in pump only hpa systems, especially so with the cheaper pumps. Hydraulic shock (aka water hammer) is something you may encounter, its commonly caused by the operation of a DDSV. An accumulator can solve these issues, the benefits of having one in the system are numerous. I wish you every success with your design and look foward to hearing how it performs.


#12

Yes, we will see.:grinning:
Watter hammer is esential for my sistem, it provide fast rising slope of spraying pulse.


#13

You have quite a list of theories to test. water hammer is never a good thing :wink: If you
look at your system diagram and consider what happens when the DDSV closes. All of the lines have to be pressurised by the pump from 0psi to the adv opening pressure, of lets say 35psi, before you get any mist.
During this phase the lines will tend to move (energy lost to movement) and expand in size slightly (more volume) with the pressure increase. You should avoid using any soft tubing, garden hose etc in the system for this very reason .These events will delay the system reaching the required pressure so instead of taking the theoretical 0 seconds to reach the adv opening pressure, it will take longer, optimistically 0.5 seconds but probably closer to 1 second. The nozzles wil only have 0.5 seconds left on the timer to reach full operating pressure and deliver the mist.
When the nozzles open, the flowrate demand increases and the pump must respond instantly or the line pressure will dip by a fraction of a psi (another small delay). Note that doubling the flowrate results in a 4 fold increase in the line losses…
You will find the system losses and hydraulic delays, however small, will conspire to make the theoretical response time impossible The 1 second cycle will not provide enough time for the nozzles to reach full pressure and deliver adequate mist quality, a minimum of 3 seconds is typical for pumped systems,
if i get a spare minute over the weekend i`ll set up a pump with DDSV to drive one of my towers, 4x hypro nozzles with adv on a ring manifold and put up a video of the performance. I can say for sure it wont match the response of the accumulator driven tower.
AA has by far the fastest response of all the aero methods, a 1 second repeating cycle is well within their capability even though you wouldnt use it for anything :wink:


#14

Has anyone tried with Air Spray Gun: Look at this on eBay http://www.ebay.co.uk/itm/263147142022
These have nozzle only 0.5mm.


#15

Paint sprayers, air brushes, oil burner nozzles, rotary disc atomisers etc have all been tried before. Paint sprayers dont have the output, throw distance or technical documentation of expensive AA nozzles but they are cheap. If you plan to give it a go you`ll need at least 2 for a small chamber and, of course, an air compressor to run them. The sprayers will consume a lot more air than a typical AA nozzle, between 35 and 70 cubic feet per day (1000-2000L) per gun. A silent air compressor is essential if noise is an issue as it can and will run at any time of the day or night.


#16

I can get these Lechler for ~$150

PDF


#17

Judging by flowrate and pressure, you`d need 2 nozzles. Compared to the paint sprayer on the same cycle timing they would consume approx 23 cubic feet (650L) each per day. Be aware these nozzles are pressure fed nozzles which require pressurised liquid as well as air. The cheapest method is to fit another regulator to the output of the compressor and use air to pressurise liquid in a 19L cornelious keg. The alternative is to use a pump, accumulator and pressure reducer. The keg will provide roughly the same liquid capacity as an 8 gallon (30L) accumulator. Before choosing a nozzle you will need the droplet size distribution data, which the tech support dept will provide on request.


#18

For now, this is far far away option. Posted for other, who thinking about AA.
To use air to pressurise liquid was also my idea :grinning:


#19

In my experience, most folks dont progress much beyond than the idea or thinking stage. You`ll find very few folks with hands on experience of AA and even fewer that are willing to share information.