My Arduino & LEDs

SameSane said:

Some Grow Data on the other Hand is very hard to monitor. Like Soil Moisture, which I need to be aware of. There are millions of different soil moisture sensors, and I tried a few, but there were always horribly wrong. An alternative could be to weigh your pots and compare your current weight with the weight after watering. But this is also very messy.

Click to expand...

You were probably using resistive sensors, which like a capacitive sensor, are said to be used to measure "soil moisture", but are actually measuring soil water potential, which is a combo of gravimetric water potential, osmotic water potential and matric potential......neither actually measures physical capacity of water and measuring by weight, doesn't either, because you have to know your osmotic and matric potentials to be able to asses that.

Capacitance sensors are generally more reliable than a resistive sensor in orders of 10 but then that measurement has to actually be converted, for it to relate to any kind of qualitative data rendering soil moisture contents.

Yeah, a capacitive moisture sensor works much better. It's a bit difficult to interpret the values though. The high frequency ones are better than low frequency.

I feel the measurements from a tensiometer are a bit more easy to understand:


Normally I would use one per pot though

wietefras said:

Yeah, a capacitive moisture sensor works much better. It's a bit difficult to interpret the values though. The high frequency ones are better than low frequency.

I feel the measurements from a tensiometer are a bit more easy to understand:
View attachment 3581170

Normally I would use one per pot though

Click to expand...

Nice dude, I have seen the tensiometer from Blu....rather nice....I was going to suggest in your thread, so I have you here now, rather ask, whether you thought about correlating VPD to gravimetric potential at Night, heck even a correlation could be derived from a local area moon chart and my theory is that you could quantify that with your rising VPD especially at night...Even another simpler trick, although the measuring may need to be too ultra precise, is to raise one pot above another and see if VPD has any difference through the night as a higher pot in theory will be affected less by gravity and hence a lower gravimetric potential......and true Soil Water Content to boot, not potential....

Thats my only complaint again about the tensiometer, great devices, but they only measure potential again....

Gravimetric
Neutron Scattering
and
Time Domain Reflectry [TDR] are the typical ways to measure Soil Water Content instead of Potential.... there is at least one other way, that might hold potential....

and none of them are really cheap or applicable for static testing imho....Gravimetric samples need to be destroyed to get real data, neutron scattering is questionable and TDR might hold the most promise in the future, but not exactly household at the moment

wietefras said:

Yeah, a capacitive moisture sensor works much better. It's a bit difficult to interpret the values though. The high frequency ones are better than low frequency.

I feel the measurements from a tensiometer are a bit more easy to understand:
View attachment 3581170

Normally I would use one per pot though

Click to expand...

These are badass though...best DIY I have seen maybe ever...thanks for posting your ideas

Abiqua said:

Nice dude, I have seen the tensiometer from Blu....rather nice....I was going to suggest in your thread, so I have you here now, rather ask, whether you thought about correlating VPD to gravimetric potential at Night, heck even a correlation could be derived from a local area moon chart and my theory is that you could quantify that with your rising VPD especially at night...Even another simpler trick, although the measuring may need to be too ultra precise, is to raise one pot above another and see if VPD has any difference through the night as a higher pot in theory will be affected less by gravity and hence a lower gravimetric potential......and true Soil Water Content to boot, not potential....

Thats my only complaint again about the tensiometer, great devices, but they only measure potential again....

Click to expand...

No, I have never considered looking into gravimetric effects. How do you figure that would be related to VPD though? I don't see how that could influence temperature or humidity levels?

Lifting the pot doesn't have an effect on the tensio values. Lifting the sensor higher out of the pot does have an effect, because it creates a column of water that's sitting on the ceramic cone.

I have some capacitive sensor laying around, but I switched to hydro so I never actually tried them. Form what I understood a capacitive meter needs to be calibrated for the specific soil your using and a tensiometer you simply aim for 80kPa. Field capacity (soak the soil and wait for gravity to pull excess water out) should be around 30kPa.

I would like to put both in the pot and check if indeed the capacitive percentage measurements differ per type of soil compared to the tensiometer measurements. They couldn;t sit too close to each other though. The capactive sensor might be influenced by the water in the tensiometer

Gravimetric
Neutron Scattering
and
Time Domain Reflectry [TDR] are the typical ways to measure Soil Water Content instead of Potential.... there is at least one other way, that might hold potential....

and none of them are really cheap or applicable for static testing imho....Gravimetric samples need to be destroyed to get real data, neutron scattering is questionable and TDR might hold the most promise in the future, but not exactly household at the moment

Click to expand...

The newer high frequency capactitive sensors actually use some form of TDR. They are not that expensive.

For instance the Vegetronix VH400 or perhaps the I2C Soil moisture sensor. For the last one I think he said he was still working on a higher frequency version. Not sure if he finished that already.

If I start growing in soil again, I will 3D print some housing for the sensor. That should look a lot better than this high pressure PVC piping

Hey guys. I've also been working on a micro-controller to use for automation. I'm not going the open source route (sorry) but am definitely going the low cost route. I'm focused right now on EC/pH and I've calculated my costs, and even on my low volume runs, I can crush BluLabs as far as price is concerned. My hardware is in transit from China (taking forever) so I can build a prototype. But I do have an ugly-ass HMI that can simulate the hardware and a reservoir so you can test it out, if anyone is interested. I would love some feedback if any of you want to try it out as I'm getting ready to put it on KickStarter.