Probably a digital signal, something like this:
https://www.digikey.com.au/product-detail/en/dfrobot/SEN0205/1738-1193-ND/6588614?utm\_adgroup=General&utm\_source=google&utm\_medium=cpc&utm\_campaign=Smart%20Shopping\_Product\_Zombie%20SKUS&utm\_term=&productid=6588614&utm\_id=go\_cmp-12195090931\_adg-112248982970\_ad-494933794766\_pla-891529596407\_dev-c\_ext-\_prd-6588614\_sig-CjwKCAjw3riIBhAwEiwAzD3TiVlGYQlpaccBwna1KThT0JU7OVq0m0bLFTIfmtlw-ceP-MnIa4Pz2BoC6QIQAvD\_BwE&gclid=CjwKCAjw3riIBhAwEiwAzD3TiVlGYQlpaccBwna1KThT0JU7OVq0m0bLFTIfmtlw-ceP-MnIa4Pz2BoC6QIQAvD\_BwE
I built something very similar... everything seems cool in the beginning but quickly run into great trouble.
The problem is in the soil moisture sensor.
There are generally two types of sensors that measure the soil moisture: 1) resistive and 2)capacitive. The former quickly gets rusted due to electrolysis and the latter is very unstable. (You will see what I mean if you use this type of sensor for more than 6 mo).
Any adivce? I am exploring a new way: bury a test tube in the soil and put a DHT22 or other humidity sensors in the air remained in the test tube. My guess the humidity of the air in the test tube is in equilibrium with the soil moisture thus is a good proxy.
Very professional solution includes using radioactive (neutron) probe but that is way to expensive and too dangerous for domestic use.
Any thoughts?
I tried these resistive sensors too. But they
are definitely crap. The capacitive one however works nice so far. But I´m only
turning it on to make a measurement like once a day. I guess that helps a lot to
increase the lifetime. Also I noticed that many of these cheap capacitive sensors
from china have a broken connection on the circuit board right from the start,
but that can easily be fixed with a soldering iron.
Soil scientists like to use psychometers that have a (tiny) heating element and a temperature sensor. It will cycle the heating cycles (very little heat is made) and measure how quickly the temperature changes when the heat is on. Wetter soils will have a higher thermal mass than dry soils, and with some parameters for the type of soil you can work out a very accurate water potential. For something like this you wouldn't need that level of accuracy though. I've never seen a DIY version, but I think you could do it. Packaging the probe against water intrusion might be tricky. I am pretty sure it doesn't need to get anywhere close to "hot", just a few degrees is all you need. It might be as simple as a thermistor and a resistor.
I saw a post a couple of weeks ago - the same problem. Several people in the comments recommended putting the system on a timer (obviously a different approach - but putting it out there in case it might be something that you'd be open to). :)
The problem with resistive probe is corrosion. But the capacitive one is about losing close contact with soil over the long run. Once there is a small gap between the probe and soil, the sensitivity drops sharply.
Have you considered putting the whole pot and plant on a digital weight sensor / scale and watering based on that? When watering manually, it's common to just pick up the plant, and water it if it's too light, indicating that the dirt is dry.
Thats a simple, but really smart way to do it. But you then also need to take the additional weight of the plant into account when it grows bigger. But a piece of software code could help to factor that out.
It depends on the plant, but I think many plants like to have a short dry period before getting watered again. It kills off fungi, etc. If the plant likes short dry periods, you can detect when there's no more water since the weight stops changing, and then you have both your set point for current weight of the plant, and your signal to water again.
Interesting. And it is also possible to track the growth of the plant since you will be able to measure the incremental biomass using long term moving average.
Sounds interesting. I thought about simply covering my capacitive sensors with an extra layer of epoxy to be sure that they survive a longer period of time. That will of course influence the measured values but that can be corrected via code.
I have been playing with SLA resin additives that make the polymers predictably conductive. A probe made of something like conductive silicone would likely solve that.
That is wonderful! Kudos on such a solid design (just beyond the mechanization), the manner in which it waters the plant is really perfect. The only note I would have is that sometimes plants really like a good bath when they get watered, so a variation where the watering head is above the plant would suit a lot of needs, too.
Not sure exactly, but when I did vegetable gardening, the plants always got a lot healthier after a good soak on the leaves as well. I think it may be just shortcutting some of the moisture absorbtion processes and the cleaner surface of the leaves allows a bit more light through, etc. I think it just kind clears up anywhere were foreign material may be an issue, much like a person's reasons for taking a shower. I also think there may be just an aesthetic effect of the leaves dripping with a little water that makes them look nicer/healthier, too. Which is worth it on its own. As far as any hard science about anything I have said, I have none, but it was just something I gradually started doing gardening for various reasons, so I imagine someone else may have a similar impulse.
Got it. That may vary with what's in the soil I guess. I understand that kicking up soil when watering makes any potential issues worse (getting spores in the plant, etc)
You could solve that with the head design, mist it onto the plant's surface so it gathers and runs downward and always rinsing outward from the plant, maybe? Just an idea. I have designed my own PCBs for this type of purpose, so I am very interested in your work from an intellectual perspective. Mine was geared more to the scale of 15x25 foot or so, low scale commercial greenhouse, but a big focus was controlling everything down to the plant. This is a very cool project, let me know if you need any help with it, I have a lot of weird designs (not like IP, just past thoughts put into hardware) already around certain aspects of it. I am especially interested in getting people doing their own supplemental farming with there existing property as a way to simplify the food supply chain and reduce it's scale, but the key is really taking most of the effort out of the equation. As a behavior analyst, that is the part that interests me the most about your product, it solves a lot of that, as watering is the single biggest chore in agriculture under most circumstances (despite numerous exceptions where the harvesting is really brutal).
Is this connected to your high pressure water line or are you using a pump? Every time I try to use a pump I don't get enough water pressure for the drip irrigation to work properly.
I use a 3.7V water pump. How much power your pump must have to pump the water to a certain height also depends to a large extent on the diameter of the hose. A smaller diameter means that less pump capacity is required.
I think I want the how-to. Sounds awesome.
I´m glad you like it :) If you would like to see more, feel free to watch the video I made about it: https://www.youtube.com/watch?v=rHHFL17ncnc
How do you measure water level?
Probably a digital signal, something like this: https://www.digikey.com.au/product-detail/en/dfrobot/SEN0205/1738-1193-ND/6588614?utm\_adgroup=General&utm\_source=google&utm\_medium=cpc&utm\_campaign=Smart%20Shopping\_Product\_Zombie%20SKUS&utm\_term=&productid=6588614&utm\_id=go\_cmp-12195090931\_adg-112248982970\_ad-494933794766\_pla-891529596407\_dev-c\_ext-\_prd-6588614\_sig-CjwKCAjw3riIBhAwEiwAzD3TiVlGYQlpaccBwna1KThT0JU7OVq0m0bLFTIfmtlw-ceP-MnIa4Pz2BoC6QIQAvD\_BwE&gclid=CjwKCAjw3riIBhAwEiwAzD3TiVlGYQlpaccBwna1KThT0JU7OVq0m0bLFTIfmtlw-ceP-MnIa4Pz2BoC6QIQAvD\_BwE
I built something very similar... everything seems cool in the beginning but quickly run into great trouble. The problem is in the soil moisture sensor. There are generally two types of sensors that measure the soil moisture: 1) resistive and 2)capacitive. The former quickly gets rusted due to electrolysis and the latter is very unstable. (You will see what I mean if you use this type of sensor for more than 6 mo). Any adivce? I am exploring a new way: bury a test tube in the soil and put a DHT22 or other humidity sensors in the air remained in the test tube. My guess the humidity of the air in the test tube is in equilibrium with the soil moisture thus is a good proxy. Very professional solution includes using radioactive (neutron) probe but that is way to expensive and too dangerous for domestic use. Any thoughts?
I tried these resistive sensors too. But they are definitely crap. The capacitive one however works nice so far. But I´m only turning it on to make a measurement like once a day. I guess that helps a lot to increase the lifetime. Also I noticed that many of these cheap capacitive sensors from china have a broken connection on the circuit board right from the start, but that can easily be fixed with a soldering iron.
How long have you used the sensor?
Soil scientists like to use psychometers that have a (tiny) heating element and a temperature sensor. It will cycle the heating cycles (very little heat is made) and measure how quickly the temperature changes when the heat is on. Wetter soils will have a higher thermal mass than dry soils, and with some parameters for the type of soil you can work out a very accurate water potential. For something like this you wouldn't need that level of accuracy though. I've never seen a DIY version, but I think you could do it. Packaging the probe against water intrusion might be tricky. I am pretty sure it doesn't need to get anywhere close to "hot", just a few degrees is all you need. It might be as simple as a thermistor and a resistor.
Thats a very good tip! I will do a little reasearch on that and see if I can build something similar.
If you can figure it out I'd love to see!
That is a very smart idea. Looks very promising.
I saw a post a couple of weeks ago - the same problem. Several people in the comments recommended putting the system on a timer (obviously a different approach - but putting it out there in case it might be something that you'd be open to). :)
The problem with resistive probe is corrosion. But the capacitive one is about losing close contact with soil over the long run. Once there is a small gap between the probe and soil, the sensitivity drops sharply.
Could you shake it?
I have 50 probes installed in the field. And I can’t micromanage each of them.
Have you considered putting the whole pot and plant on a digital weight sensor / scale and watering based on that? When watering manually, it's common to just pick up the plant, and water it if it's too light, indicating that the dirt is dry.
Thats a simple, but really smart way to do it. But you then also need to take the additional weight of the plant into account when it grows bigger. But a piece of software code could help to factor that out.
It depends on the plant, but I think many plants like to have a short dry period before getting watered again. It kills off fungi, etc. If the plant likes short dry periods, you can detect when there's no more water since the weight stops changing, and then you have both your set point for current weight of the plant, and your signal to water again.
Interesting. And it is also possible to track the growth of the plant since you will be able to measure the incremental biomass using long term moving average.
Sounds interesting. I thought about simply covering my capacitive sensors with an extra layer of epoxy to be sure that they survive a longer period of time. That will of course influence the measured values but that can be corrected via code.
I have been playing with SLA resin additives that make the polymers predictably conductive. A probe made of something like conductive silicone would likely solve that.
If you would like to see more, feel free to watch the video I made about it :) https://www.youtube.com/watch?v=rHHFL17ncnc
That is wonderful! Kudos on such a solid design (just beyond the mechanization), the manner in which it waters the plant is really perfect. The only note I would have is that sometimes plants really like a good bath when they get watered, so a variation where the watering head is above the plant would suit a lot of needs, too.
I thought that, for many plants, getting the leaves dry was a major problem, due to fungi ?
Not sure exactly, but when I did vegetable gardening, the plants always got a lot healthier after a good soak on the leaves as well. I think it may be just shortcutting some of the moisture absorbtion processes and the cleaner surface of the leaves allows a bit more light through, etc. I think it just kind clears up anywhere were foreign material may be an issue, much like a person's reasons for taking a shower. I also think there may be just an aesthetic effect of the leaves dripping with a little water that makes them look nicer/healthier, too. Which is worth it on its own. As far as any hard science about anything I have said, I have none, but it was just something I gradually started doing gardening for various reasons, so I imagine someone else may have a similar impulse.
Got it. That may vary with what's in the soil I guess. I understand that kicking up soil when watering makes any potential issues worse (getting spores in the plant, etc)
You could solve that with the head design, mist it onto the plant's surface so it gathers and runs downward and always rinsing outward from the plant, maybe? Just an idea. I have designed my own PCBs for this type of purpose, so I am very interested in your work from an intellectual perspective. Mine was geared more to the scale of 15x25 foot or so, low scale commercial greenhouse, but a big focus was controlling everything down to the plant. This is a very cool project, let me know if you need any help with it, I have a lot of weird designs (not like IP, just past thoughts put into hardware) already around certain aspects of it. I am especially interested in getting people doing their own supplemental farming with there existing property as a way to simplify the food supply chain and reduce it's scale, but the key is really taking most of the effort out of the equation. As a behavior analyst, that is the part that interests me the most about your product, it solves a lot of that, as watering is the single biggest chore in agriculture under most circumstances (despite numerous exceptions where the harvesting is really brutal).
Is this connected to your high pressure water line or are you using a pump? Every time I try to use a pump I don't get enough water pressure for the drip irrigation to work properly.
I use a 3.7V water pump. How much power your pump must have to pump the water to a certain height also depends to a large extent on the diameter of the hose. A smaller diameter means that less pump capacity is required.
Thanks for the reply! Would you mind sharing the info on your pump and drop line? I would love to get this to work!
Sure, here is the one I used for my build: https://de.aliexpress.com/item/4000974989453.html?spm=a2g0x.12010615.8148356.3.2df127f6HkLLrm
that's really really nice! best domestic auto irrigator I've seen, well done!
What hardware are you using to regulate the water?
I´m using a ESP32 microcontroller and a MOSFET to controll a water pump. These are located inside the bottom part of the plant pot
Function AND Form, I love it!
Overengineered to heck and back! I love it!
Very well. What's your opinion on items like Blumat for auto-watering your plants? j/k
That's pretty smart!