Soil-Moisture sensor

[Toulon7559]

Tindie.com has some interesting add-ons for Raspberry, for Arduino, etc., like this soil-moisture-sensor:
https://www.tindie.com/products/aprbrot ... rod_search

[Flopp]

https://www.mysensors.org/build/moisture

If you like to have sensors to Domoticz i can highly recommend using MySensors. You can use almost any sensor with MySensors and data are transferred wireless.

[Toulon7559]

For meteo-applications the soil moisture sensor should report (with reasonable accuracy) the actual moisture-content, not an indication whether 'the plants need to be watered'.
In that perspective the offer by Tindie is more appropriate for meteo-info than many other offerred devices which threshold an incoming analogue signal and produce an indication when the threshold is passed.

[Toulon7559]

The moisture probe (incl. ESP8266) as offered by Tindie can also be found here at AliExpress.
Looking around in the catalogue of AliExpress (and others) also (much) cheaper solutions available.
This sensor-device has both an analogue output and a digital output:
- the analogue output is proportional to moist content measured between the 2 legs of the probe, and is compatible with the analogue interface of ESP8266, Arduino, etc. Considering the principle of measurement and the technical layout probably better to apply it just as an indication, not for 'serious' measurements.
- the digital output reports whether the analogue signal is below or above the threshold (arbitrarily) set by means of the poti.
Also available is a probe with analogue output directly from the probe, but I doubt the lifetime of such design, because so close to soil the environment is bad for electronics. Anyway, for outside application you must extra protect the electronics agains rain etc., because otherwise malfunctions can quickly be expected.
On the other hand, for that price ordering a few more probes as spares is not a heavy burden ......

If you want to measure deeper in the soil and/or more seriously, you have to apply more expensive sensors:
looks like an 'underground' version of DHT11/DHT22. A waterresistant enclosure probably is useful for (some) extension of lifetime.

[Toulon7559]

To check the temperature and humidity in the space under my house, I 'planted' and installed a 'fork'-probe and a DS18b20-probe in the soil (see webpage), with the 'fork'-probe connected to the analogue port of an ESP8266 with ESPEasy.
Precalibration reveals that 100% water ~500 units and 0% water ~1000 units.
With formula (1024-%value%)/5 that results from the ESP8266 in an output signal of approx. 0 till 100.
The picture below is the output graph in the past hours as log-picture by Domoticz: if feeling by hand the sandy soil is 'semi-dry'.

Probe_output

chart_bodemvocht170211.jpeg (53.01 KiB) Viewed 6999 times

The reported values show heavy fluctuations: any explanation?

Anyway the registration supports the already assumed functional performance of this 'fork'-probe-concept:
sufficient for rough checking whether the plants really need water, but not much better.

[Toulon7559]

Finding a sensor which has longer lifetime for affordable cost is a challenge.

AliExpress now offers an affordable capacitive sensor with analogue interface.

This RS485-device from Tindy may also be a suitable solution to measure soil moisture (and temperature near the soil).
As indicated in the description, this configuration by application of RS485-interfacing is more able to cope with setups with long cables between the sensor(s) and the processing computer. Price is far beyond the price of the other devices.

In personal opinion a less desirable aspect for both concepts is that the electronics are unprotected and very close to the moist soil.

[pvm]

Would the xiaomi mi flora be an option. This is a Bluetooth device which runs stable with no fluctuations like your graph

[Toulon7559]

@pvm

Other thread in this forum deals with implementation aspects.
This Wiki-description seems applicable for a configuration operational with Domoticz.

[pvm]

Yes, working fine

[eugen]

Hello,

I would like to measure the temperature of the soil in about 1 meter depth.

Could you please recommend some good sensor?

Thanks,

[Toulon7559]

SHT10 or better equivalent should do the job by providing temperature & moist like DHT11/22.
Protective housing to be included, to keep the moist away (to some extend).
Something like this.

When ordering, be aware (in your case) that you get a sensorhead with a connection cable of >1m length:
otherwise you have to fiddle to make a connection halfway underground.
For easy installation & maintenance in my configuration for such sensor(s), first I drilled a pipe to the required depth and then dropped the sensor to the bottom of the pipe. For periodic inspection or for cleaning, or in case of a defect, then you can simply pull out the sensor.

[eugen]

Hello Toulon,

i'm pretty confused. I found info that:
SHT1x will reach end-of-life and is only available to existing customers for support of their running production.
Last order date: 31.12.2018 / Last delivery date: 31.12.2019
We recommend the humidity sensor SHT3x as successor of SHT1x.

I think all the sensors i found on aliexpress had only 50cm cable.

Could you please advise what else is needed for wireless transmission to domoticz/raspberry, some RF transmitter in waterproof casing on top of the ground; or some WiFi transmitter?

My PI has not yet arrived.

Thanks.

[Toulon7559]

@Eugen

If order is possible till 31.12.2018 with delivery till 31.12.2019, who cares about end-of-life (unless you are 'professionally' applying this device and need to guarantee life cycle after sales support for your deliveries)?
Ali-Express at it's web-pages already asks whether you would like to have SHT2x as alternative for SHT1x:
if you want to plan ahead, take that option.

If you want to have a wireless interface to Domoticz and not afraid of DIY, (as example) apply ESP8266 with ESPEasy, in combination with your router with wifi-interface.
Then you yourself have to find a way to provide power supply to the ESP8266, and you have to protect that device against the weather.
There is an active ESP8266-forum dealing with such aspects.

[Toulon7559]

Own experience with SHT1x.

Fitted the sensor in the space under the house (= 'kruipruimte') in a holed 5/8"-pipe stretching to - 10cm below surface.
After a few months of probable submersion in wet soil, the sensor went 'foul':
no more reporting of humidity, although reporting of 'reasonable' temperature continued.

Pulled the sensor from the pipe and dried, after which the sensor happily restarted operation for both functions.

Careful conclusion from this experience:
submerged SHT1X does not provide life-long operation without problems.

For myself have decided that possibly the following approach might be more robust for 'level-survey' of the soil:
- apply one SHT1x at approx. 10cm above the soil in an aired, protected housing
- apply 2nd SHT1x in a pipe, at the surface or just under the surface for measuring humidity & temperature
- outdoors apply a 3rd (and possibly 4th) SHT1x in a pipe at a depth of approx. -10cm and -20cm (if the soil is not too wet for a long time)
- apply in separate protective pipes at -50cm and -100cm only a thermometer e.d. type DS18B20 with extra protection against moisture.
In that way you have
- temperature at all levels
- humidity above, at and under the upper layer
- possibility for pullout & repair/replace in case of malfunction