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I am new to this so forgive me if its basic. We are hardware engineers investigating the development of hardware systems to home hydroponic small gardens.

After reading a lot, I could see that there are some factors you need to keep, some of them are : ph in water, ppm, water conductivity, temperature.

I still have a few holes.

  1. I saw some simple DIY systems where people just use the Kratky method, where they put water in a box, with a little air left to the plant, and it works great without checking all of this stuff like pH, DO, E.C , etc. So, measuring them is a most, or just an enthusiasm of beginners? Do you really need that if not in a big scale?

  2. As hardware engineer i have checked all ph and E.C sensors, the basic sensor, without any circuit to analyse it, costs more then 70$ , why is that ? It's the same for E.C , so I have started to ask, can you get this data from other aspects of the water like temperature? moisture ?

Seems that turning it to be smart, costs too much for home applications.

Thanks.

  • the question is not clear: are you asking for hardware recommendations, an opinion on the cost of the equipment or what is important to monitor? – kevinsky Apr 3 '16 at 16:47
  • You can buy a cheap pH meter for about $12 from China. Conductivity, about same. I'm sure they'd be happy to sell you 10,000 units wo chasis for much less on Alibaba or similar. DO units can be pricey, but also mostly unnecessary, so long as you have a bubbler somewhere. I'm seeing boards with Arduino interface on Amazon for about $60. Certainly you can get a better bulk deal if you must have DO. You might be able to hook all these sensors to a Raspberry pi which a) runs linux and b) costs as little as $5. – Wayfaring Stranger Apr 4 '16 at 13:54
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The Kratky method works for lettuce largely because lettuce is relatively insensitive to dissolved oxygen levels and because its growing cycle completes to a point of harvest before the nutrient solution concentrates to a point of nutrient burn. It may work for a few other leafy vegetables.

If you're going to dump the whole nutrient solution periodically then you don't need do much to calculate the electrical conductivity given a known starting EC of your water source because you're starting afresh each water change. But that's expensive.

If you are going to recirculate your water, then you are going to need to measure. Otherwise you'll need algorithms based on experimentation based on crop growth, temperature, some measure of evaporative losses, plant type to calculate how to adjust the nutrient solution.

See also on root temperatures https://gardening.stackexchange.com/a/23551/1894

  • So for lettuces, if you had a big farm with rhe Kratky method, would you say its "proffesional" to not measure anything at all? – Curnelious Apr 3 '16 at 17:48
  • It's professional if you follow the methodology outlined in his papers. – Graham Chiu Apr 3 '16 at 17:50
  • Moreover, is the hardware so expensive or am i missing something? Expensive I mean when you mass production pcb's with sensors for home indoor gardens, only the hardware components would costs 130$ .. – Curnelious Apr 3 '16 at 17:50
  • I don't know anything about sensor cost – Graham Chiu Apr 3 '16 at 17:53
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Without knowing for sure, I see several things

  • You may be shopping "laboratory grade" sensors. Then again, you may need them...
  • An "EC" sensor may require platinum or other exotic/expensive material to remain stable in constant contact with the nutrient solution. Using copper electrodes would be subject to corrosion, contaminating the solution with copper and also changing the behavior of the sensor over time.
  • For a large scale hydroponic operation (greenhouses) this is not a large cost.
  • For a smaller scale illicit operation it's also not a large cost. I don't know about your area, but every "hydroponics shop for the small-scale grower" I've seen pop up is either IN a "head shop/smoke shop" or gives off the same vibes. There surely are some folks using them for legit purposes on a small scale, but...
  • There likely isn't a particularly large set of users not fitting the above two conditions to drive high-volume, low cost sensors.
  • You might (or might not) find lower cost sensors that MIGHT be adaptable to hydroponic use in a (slightly) higher volume market, such as marine aquaria.

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