Mega plus board with ESP 32

Posted by: @inst-tech

I also would recommend capacitive type soil sensors as they would last much longer than resistive types that are prone to corrosion of the probes due to electrolysis. here a link to capacitive sensors .. https://www.circuitschools.com/interface-capacitive-soil-moisture-sensor-v1-2-with-arduino-lcd-and-oled/

Great link.  If you (or anyone) know about these, I have a couple of questions...

1. The part in the dirt is totally sealed with non-corrosive paint/plastic/epoxy/Xxxxx so it won't corrode?
2. The top part seems exposed especially since water/other stuff is being sprayed around.  What kind of heat does it generate... can it be coated in epoxy or say... melted, scrap ABS which I have in butt-loads from failed 3D designs/prints.  Or will it cause too much insulation and overheat OR will it change the capacitive aspects and cause it to fail?
3. I noted in the link that it re-affirms that water does not conduct, but needs the minerals/ions to change the capacitance.  What kind of variability does it have with the range of "moisture" that it will experience - distilled water, city water, my hard well water, ... hydroponic solutions? 

@inq It says water does not conduct electricity? That is not what I know to be true.

@dastardlydoug - I don't want to sway you too far from your vision, but just want to throw out a different architecture for future reference.  You know the saying, "If you have a hammer, everything looks like a nail."  I'm kind of that way.  I like my ESP8266's and have lot's of experience with them.  I also like to use the divide and conquer concept.  Instead of having some single CPU controlling lots of wired sensors.  I'd rather make them single CPU/single function "modules" and combine them logically in the network world.  

Have you scoped out how long of runs you will have, say... from your processing unit and the fine little sensor wires going out to the various moisture and tank sensors.  You may find long runs on sensors may not work.

In your example project, another architecture type might be single point use based.  If one failed... all others would still work.  Here is what I'm suggesting...

Parts

"https://www.amazon.com/ACEIRMC-ESP8266-Internet-Development-Compatible/dp/B09H6K2JQY/"

https://www.amazon.com/ACEIRMC-ESP8266-Internet-Development-Compatible/dp/B09H6K2JQY/

"https://www.amazon.com/Shield-Module-Channel-Compatible-Arduino/dp/B093LC9DNJ/"

https://www.amazon.com/Shield-Module-Channel-Compatible-Arduino/dp/B093LC9DNJ/

"https://www.amazon.com/AITRIP-Capacitive-Corrosion-Resistant-Electronic/dp/B094J8XD83/"

https://www.amazon.com/AITRIP-Capacitive-Corrosion-Resistant-Electronic/dp/B094J8XD83/

Each Module would have the single Relay Shield plugged into the WeMos.  No wires, no 3.3 to 5V issues... easy-peasy. 😉  Connect the moisture sensor to the analog pin and your done.  I have a 3D printer, so I'd also make a housing that would hold the WeMos, Relay, with just the buisiness end of the moisture sensor sticking out and even incorporate the pump all in one plastic housing.  Stick the Module's probe in the ground and hook up the power and water lines.  Rinse and repeat for all 8 channels. 

You then write the software to handle just one sensor / one relay pump.  Each device would easily sense, report and be controlled independently of all the others.  

Likewise, if you had various sensors in the tanks - do pH, temperature, quantity, etc... have one ESP8266 or ESP32 and those sensors.  This tank Module would report independently to the cloud and/or to some house centric computer... say a RasPi that could host a database to keep history and or make global decisions that the various watering and tank modules would then carry out. 

As you can see this basic design is scalable to a ninth box or 100th without change of hardware or software.  

VBR,

Inq

Posted by: @zander

@inq It says water does not conduct electricity? That is not what I know to be true.

Pure, distilled water does not!  City, rain, well, lake, ocean water certainly does.  😉 

@inq For me if someone gets some basic science wrong then all their other words are noise to my ears. Obviously a marketing type wrote that nonsense.

Posted by: @inq

Posted by: @inst-tech

I also would recommend capacitive type soil sensors as they would last much longer than resistive types that are prone to corrosion of the probes due to electrolysis. here a link to capacitive sensors .. https://www.circuitschools.com/interface-capacitive-soil-moisture-sensor-v1-2-with-arduino-lcd-and-oled/

Great link.  If you (or anyone) know about these, I have a couple of questions...

1. The part in the dirt is totally sealed with non-corrosive paint/plastic/epoxy/Xxxxx so it won't corrode?
2. The top part seems exposed especially since water/other stuff is being sprayed around.  What kind of heat does it generate... can it be coated in epoxy or say... melted, scrap ABS which I have in butt-loads from failed 3D designs/prints.  Or will it cause too much insulation and overheat OR will it change the capacitive aspects and cause it to fail?
3. I noted in the link that it re-affirms that water does not conduct, but needs the minerals/ions to change the capacitance.  What kind of variability does it have with the range of "moisture" that it will experience - distilled water, city water, my hard well water, ... hydroponic solutions? 

@inq, I will try to address those issues you have brought up in the above quote..

As my experience is with industrial grade instrumentation (sensors), I'm not to use that those hobby sensors are made for that purpose, but, having said that, you could do the following  as per the instructions in https://forum.dronebotworkshop.com/help-wanted/mega-plus-board-with-esp-32/paged/7/#post-29874 :

• To make the sensor last long apply nail polish enamel on the sides of the open silicon chip to protect from water.
• Use a silicon glue or some tubing to protect the circuits above the warning line as they are not water proof. 

A capacitive moisture sensor works by measuring capacitance changes caused by the changes in the dielectric. It does not measure soil moisture directly (as pure water does not conduct electricity well), instead it measures the ions that are dissolved in the moisture. Capacitive measuring basically measures the dielectric that is formed by the soil and the water is the most important factor that affects the dielectric.

So this means to more ions the moisture contains the the higher the dielectric will be, so it's a function of mineral content (ions) rather than moisture.. and yes, water doesn't conduct very well if it has low mineral content.. the reason why we de-mineralize water for steam boiler operation to prevent corrosion due to electrolysis and chemical reaction. Ionized water have very low conductivity..

hope this helps you with your questions..

regards,

LouisR

@inst-tech @Inq I think you both missed the OP's point. He doesn't want the resistive types because he believes that they will leach lead from the solder joints.

I won't comment on the validity of his belief because it is just a belief. 

Posted by: @zander

@inq For me if someone gets some basic science wrong then all their other words are noise to my ears. Obviously a marketing type wrote that nonsense.

I'm not quite sure if you're referring to the article or me... 😆 

I learned that in high-school Physics and again in Chemistry.  Even if I learned that in the last century, I'm pretty sure the rules haven't changed.  Maybe you need a more reputable source - https://www.scienceabc.com/pure-sciences/do-you-think-that-water-conducts-electricity-if-you-do-then-youre-wrong.html#:~:text=minerals%20and%20impurities.-,Pure%20water%20does n't%20conduct%20electricity,water%20does%20not%20conduct%20electricity.

... or are you one of those flat-Earth people?  😉 

@inq He said very early on he didn't want to use resistive because of the solder. So my comment was intended to point out you don't need to 'sell' him on capacitive, he already made that decision. 

@inq Of course it isn't flat, everybody knows it's hollow.

My objection was with the article, no disrespect intended towards you. If anyone truly thinks water isn't a good conductor and I mean just plain old tap water, not some esoteric variety few of us have at our disposal then get an insulating rubber mat, put it in a pool of water, stand on it and now grab a high voltage line. Send me a picture when you do and I will be convinced.

@zander Ron, no one is saying water will not conduct, it's just a poor conductor if it doesn't contain a lot of minerals (ions).. I worked with demineralized water quite a bit for the 40 years in plan demineralizers where we take out the minerals to make boiler feed water..This make the water suitable for feed water and the conductivity of that water is practically zero.. Ordinary tap water can be several 100 S/m  (S/m, U.S customary unit is milliohms per centimeter) to several thousands S/m ..

The ability of water to conduct an electric current is known as EC or Electrical conductivity of water. Chemicals or salts break down and dissolve in the water as positive and negative charged ions and these free ions in water conduct electricity. As a result, water electrical conductivity depends upon the concentration of ions. 

Here's an interesting article about water conductivity if your interested..

https://www.vedantu.com/physics/conductivity-of-water

Hope this helps you understand what we're saying about water and it's conductive properties..

As far as whether or not we missed the OP's point, I was merely giving @dasterlydoug some information on capacitive type soil sensors and specifically how to use them as the url give a great explanation of how to wire up, code, calibrate, and even weather proof the sensor.

kind regards,

LouisR

@inst-tech OMG, I fear I am guilty of not reading entire posts but skimming. My apologies for being a poor forum member, I will do my best to slow down and read AND understand everything I see.

@zander No apology necessary my friend..we are all guilty of do exactly that, not fully reading, or comprehending what we have read..I'm 75 now, so a bit younger than you are, but fully understand that at our respective ages.. at times we just get frustrated and become that ol' curmudgeon that we both dislike... lol  Your a great resource to the forum, and I've learned a lot from you, and the others , especially Bill.. Hopefully, many others are reading our banters and are benefiting from the discussions..keep 'em coming,

We'll all learn together..after all, isn't that what this forum is all about?

kind regards,

LouisR

@inst-tech Thank you for understanding. I would kill to be 75 again LOL.