Considering switching from PPM to EC, need advice.

Eric Farley said:

I have been growing for a little over a year now and thus far I've always used PPM meters to measure my nutrient concentrations, however I've recently been designing and building an Arduino automated nutrient monitor and the only probe I could find was an EC probe. I was thinking about just converting EC to PPM using a standard conversion formula, but the more I read the more I hear about how inaccurate that conversion is. The only hesitation I have is I don't have any experience or knowledge of it.

My question for you guys is has anyone else made a switch from PPM to EC, if so did you notice a difference in the health of the plants or quality of the final product?

Also was it difficult to find the appropriate EC for the plants? I imagine all I need to do is increase the EC around .2 EC per week instead of 100 PPM and watch for signs of nute burn, but that's just me using the conversion from EC to PPM to figure out what the equivalent value in EC would be to 100 PPM.

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firsttimeARE said:

How is the arduino coming along? I saw your post on some arduino forum as im trying to build a pH doser as well.

Saw the nMe e farley and thought it sounded familiar.

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Eric Farley said:

I figured using EC was that simple, I was just concerned I was missing something since people rag on PPM for being so inaccurate, but I suppose it's really just that unless you provide both the ppm and the conversion factor the ppm value could be a number of EC values.



It's going well, I've gotten the wiring and parts list all sorted, I'm about 75% done with the code and I should be doing my first tests of the EC side of things tonight. I'm waiting for a bunch of things to arrive in the mail to move on to the next steps. I have a pH meter that seems good, but I can't test it as I didn't have a 10.01 pH reference solution which is required for calibration. Turns out the local shops only sell 4.01 and 7, so 10.01 is in the mail.

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firsttimeARE said:

I followed rezas build and all he used was 7.0 and 4.0 and recorded the temp at 4.0 cause i guess that matters

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Eric Farley said:

It seems that different probes have different calibration requirements. The hand held pH meter I have from blueLabs that I've used the last year uses 4 and 7 for calibration. The probe I selected that works with Arduino uses 4 and 10.

Also one thing that seems important is you can't use just any pH meter, most of the ones you find are laboratory probes which are designed to take a reading and be removed from the solution. Extended submersion will destroy the probe. To leave the probe in 24/7 you need to purchase an industrial probe which are more expensive. Although regular cleaning may make a lab device okay, but the whole point of automating this to get get rid of the daily work.

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Eric Farley said:

It seems that different probes have different calibration requirements. The hand held pH meter I have from blueLabs that I've used the last year uses 4 and 7 for calibration. The probe I selected that works with Arduino uses 4 and 10.

Also one thing that seems important is you can't use just any pH meter, most of the ones you find are laboratory probes which are designed to take a reading and be removed from the solution. Extended submersion will destroy the probe. To leave the probe in 24/7 you need to purchase an industrial probe which are more expensive. Although regular cleaning may make a lab device okay, but the whole point of automating this to get get rid of the daily work.

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The_Enthusiast said:

I used ebay like PH and EC meters, i thought they were ok, but after I switched to HANNA instruments a all-in-one:

And used their calibration, cleaning and storage solutions - i can say my results got better. It has a changeable EC/PH/TEMP "stick"
I was notified that I'll have to change it every 6 months but I used it for 3 years before change. One of better 300€ spent (device + storage/calibration/cleaning solutions for 3+years)

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firsttimeARE said:

Which Arduino tutorials were you using?

Im,currently going thru one.

Trying to figure out a starter kit to buy so I can do the exercises hands on rather than just reading them. There are so many types of boards its dizzying.

So far ive seen dosers made,from,the uno,and the mega2560.

What board are you using?

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ttystikk said:

Whoever told you that leaving either the pH probe or the EC meter in nutrient solution for extended periods will hurt them is an idiot and you should stop taking their advice.

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Eric Farley said:

Do you leave your probes in the solution 24/7 or do your remove them between checks? I'm guessing this uses industrial grade probes considering it cost so much.



I'm not really using any tutorials. I purchased the $100 starter kit directly from the Arduino website to get started learning the basics, that was moderately helpful in that it taught me some basics, gave me a stock of parts that I mostly don't have a use for and helped me learn what to do to ruin an Arduino (or what not to do ). I was later told by members of the Arduino forum that seemed very experience that whoever wrote the book it comes with lacked any solid electrical engineering background. I've mostly been learning by asking questions on forums, and reading the wiring diagrams and code examples provided from the probe manufactures.

I am using the Uno, I'm hoping I don't run out of memory on the board which would make me switch to a mega. The Uno has just enough pins for the project so it's okay there.



I've read this from multiple sources, the laboratory grade probes shouldn't be left in the solution 24/7. I'd be interested to talk with someone else who has tried to use laboratory probes for 24/7 monitoring about how long their probes lasted and how accurate they remained over prolonged submersion, but until then I wanted to make sure I had a probe designed for prolonged submersion.

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Eric Farley said:

Do you leave your probes in the solution 24/7 or do your remove them between checks? I'm guessing this uses industrial grade probes considering it cost so much.



I'm not really using any tutorials. I purchased the $100 starter kit directly from the Arduino website to get started learning the basics, that was moderately helpful in that it taught me some basics, gave me a stock of parts that I mostly don't have a use for and helped me learn what to do to ruin an Arduino (or what not to do ). I was later told by members of the Arduino forum that seemed very experience that whoever wrote the book it comes with lacked any solid electrical engineering background. I've mostly been learning by asking questions on forums, and reading the wiring diagrams and code examples provided from the probe manufactures.

I am using the Uno, I'm hoping I don't run out of memory on the board which would make me switch to a mega. The Uno has just enough pins for the project so it's okay there.



I've read this from multiple sources, the laboratory grade probes shouldn't be left in the solution 24/7. I'd be interested to talk with someone else who has tried to use laboratory probes for 24/7 monitoring about how long their probes lasted and how accurate they remained over prolonged submersion, but until then I wanted to make sure I had a probe designed for prolonged submersion.

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firsttimeARE said:

Im following a tutorial and struggling with some of the programming parts of it. Im sure by doing the exercises with an actual,arduino would help. Also going to look into another tutorial. Ive seen a couple errors in what im reading,and beginning to question the authors experience.

Im thinking of just getting the BRS 2 part doser that does a slow drip of 1.1ml/min which is really 1.8ml/min according to user review and a milwaukee mc122.

Costs $170 and doing some parts research a doser would cost about $150.

Im,going to still read up on it as its possible to control,lights, co2, pumps, pH, EC, water level all with an arduino,but rather than wait until I learn this is cheap enough. Ill just dilute my pH down on my smaller systems since theres no PLC with this system and might overshoot my setpoint.

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Eric Farley said:

If you're looking for a way to add controlled amounts of liquids look into a peristaltic pump. The one I've tested supplies 1ml/sec with a simple HIGH/LOW signal to a pin on the arduino. (you need some transistors and resistors to protect the board from being destroyed as I learned the hard way). It costs less than $10.

The one I have and tested against was $25 and I needed 6 total so I ordered some from China for $6 each. I found this link with a quick search through my history, I haven't tried this one but I think it's the one I have in the mail. http://www.ebay.com/itm/like/121372297090?lpid=82&chn=ps&ul_noapp=true

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firsttimeARE said:

http://www.bulkreefsupply.com/brs-2-part-doser-1-1-ml-per-minute.html

This was the one I was looking at. It plugs into the wall and can be operated by a simple relay.

Do you have a good sketch to use?

You said you were a programmer right?

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const motorPin = 3 // this could be any available pin.

init () {
  pinMode(motorPin, OUTPUT);
}

loop() {
  if (runPump) { // this would be some indication that you want to turn the pump on, for me it's if the PH or EC is outside the acceptable tolerance I'm giving it. This could be simple or complicated depending on how you want to determine if the pump needs to run.
    digitalWrite(motorPin, HIGH);
    delay(1000); // this can be anything, in this case I'm choosing to run the pump for 1000 milliseconds [1 second] which equals 1ml
    digitalWrite(motorPin, LOW);
  }
}

ttystikk said:

My probes last for years when left in solution.

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