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Old 05-17-2015, 04:27 AM
GpsFrontier GpsFrontier is offline
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Join Date: Mar 2009
Location: Lake Havasu AZ.
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But if I use a circulating system it won't be a uniform dose because the first plants will have more nutrition than the ones on the last end.
I think you may be misinterpreting the term recirculating. It has nothing to do with the type of hydroponic system it is, recirculating means that after the water is pumped through the system it's collected so it can be recirculated back through the system again. In a NFT system where the rows are long enough where it's possible for the first plants in the row to get more nutrients than the plants at the end of the row (rows 40 feet or longer), a secondary feed line is used half way down the row to solve the problem. And to be clear, a feed line is not a injector/doser.

If I use a circulating system I will ensure a uniform dose, all plants will recieve the same.
How? And what benefit would a injector provide?

If I flush the reservoir each night the problem you describe does not really seem to apply.
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?

So how do you automate a recirculating system if not by dosers?
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).

Computers are connected to sensors that can monitor specific variables (temp, pH, EC, co2 etc..) Depending on your computer controlled environment agriculture software system. The computer is given set parameters, and when the readings go above the max or below the minimum parameter, the computer notifies a HUMAN. In some cases it can turn on or off other systems to bring the readings back in range.

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. I haven't seen a system that can do that. Most systems will only turn on and off an injector for a specific time period that you programed it to go on for based on the water flow and EC level you set. But this only applies to NON-RECIRCULATING systems only. Each time the water passes by the sensor/injector the same amount of nutrients will be added over again and again each time.

More expensive and sophisticated systems might be able to read EC and adjust the on and off time and/or flow rate of the injector to vary the amount of nutrient being added to raise and lower EC levels (that is lower EC in NON-RECIRCULATING systems only). In recirculating systems all it can do is keep the injectors from adding more nutrients even if the EC continues to rise, and regardless of what nutrients are actually in the nutrient solution.

Large company's that use recirculating systems use computer systems to monitor parameters, and have a qualified full time person to take readings, monitor plant growth, and make needed adjustments to the nutrient solution as needed.

As I said before Non-recirculating systems are where injectors are typically used. In non-recirculating systems the flow rate of the injectors is set to create a specific EC (of balanced nutrient solution) in a flow of fresh water that is sent to the feed lines going to the plants. By NOT recirculating it you ensure the plants are getting a balanced nutrient nutrient solution all the time. The water line is controlled by a cycle timer that precisely turns on and off the water flow down to the second, that makes sure there is very little wasted water/nutrient solution.

I don't plan to change the nutriton solution every day but I want to be able to do it if I want to. The water is supposed to go back to the reservoir but I simply add a flush valve to a solenoid so every night at 3 AM the reservoir empties out and I start adding new water for the morning
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.

If I dimension the reservoir to the size of the line properly it will not be much water that empties out
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.

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