[jon1978]

Originally Posted by GpsFrontier

How? And what benefit would a injector provide?

The injector would simply prepare the nutrition content in the reservoir between 3 and 5 AM. It doesn't have to be an actual injector, it can be a pump or whatever, I just state my desire for a controller, not the actual injector or solenoid or pump or what have you.

If you run a non-circulating system you would need 100% of the nutrition to be utilized in one run in order to be profitable, if you recirculate the nutrition over a day it will most likely be more uniform because the nutrition content gradually goes down over the day as the plants use it.

First, if your going to do a nutrient change every day (nobody else would), why would you also still want to go to the trouble and expense of injecting more nutrients every time the nutrient solution passes through the system again. That would be a waste of time, money, and water. Second, If you start out with a balanced full strength nutrient solution, and run it through a system where more nutrients are added every time the the same nutrient solution passes through the system again, how does that NOT create the problem where the nutrient strength continually goes up and up?

I am not sure why you don't understand what I am going for. I want an automated system where I can specify each day what nutritients and EC I want. I want lots of N and low EC early on and then gradually more P and higher EC later on. I don't want to manually change it, I don't want to manually dose my reservoirs. In order to do it I dimension the reservoirs for one day of water use and automatically empty out the slump at night and refill it with new water and dose it before sunrise. The problem is not nutritient build-up, the problem is finding a controller that can do it. Apparantly, the only one I have found so far cost 15,000 USD which I don't want to pay when I don't have appropriate security, hence the discussion.

I am thinking of building my own PLC using a standard industrial platform and incorporate nutritient meters for N, P and K which eliminates the entire problem you describe anyway.

There is no 100% automated (set it and forget it) system that never needs attention by humans that I'm aware of, not even on the space station. Computers, sensors, injectors all have limitations. Even the most sophisticated computer controlled systems still need humans, and cost a fortune. You don't just connect a injector to a computer and expect your plants will be perfect (especially if your trying to use them in a recirculating system).

I know that but we are talking about a commercial operation where I have to do a lot of other things too. If you want a commercial grade product you cannot do it manually because it won't get a good BRIX rating without computer automation. Heard of "non tasting hydroponic tomatoes"? That's where it comes from. I need to get the water to maintain a certain level even when I am not at the site to take care of it. I cannot afford a night shift staff just because there is no PLC unit that can do it.

But when it comes to nutrient levels, there is a lot more than just EC readings to consider. If you expect your computer system to be able control the level of each mineral element, well good luck.

Well, good thing I know how to code a computer then.

I'm a bit confused here because in one sentence you say you don't want to change it every night, but in the next sentence you say your going to flush it every night at 3 AM.

You wrote "change the dosage", not "change the water". To be clear, neither applies because the dimension of the reservoir is to be aimed at a days worth so it is only the slump water that is to be flushed, not the entire reservoir. If necessary I have a backup reservoir. It is not rocket science, but it is preferable to non-circulating system.

If the water is supposed to be recirculated and going back in the reservoir, then why wouldn't their be much water left to empty out? Where is it going if it's not going back in the reservoir.

Because of the dimension of the reservoir is based on a days consumption?

What size reservoir are you planing, and what size and how many plants is it supposed to feed?

The first setup will be about 0.2 hectares split up on three systems, then I will increase it to 6-10 hectares when I have everything running but I don't want to dimension the lines until I know how much nutritients each line will consume. I don't know which aeroponics I will use for the tomatoes and pepperfruits yet, I am thinking of an Ein Gedi system which is a hybrid between aeroponics and raft.