I want to build a small system that gathers soil condition data at various depths over many years.
I wonder if the moisture and temp/humidity sensors available for Gadgeteer are durable enough to last when buried in the ground? Could I encase them In something to make them last longer without impairing their operation as a sensor?
If not, are there some other sensors out there that can be made to work with Gadgeteer that would be highly durable?
The gadgeteer moisture sensor is not relevant for your job.
Do some research and find another sensor and then come back to this forum. We can help you wire it up and get some readings.
Fun project!
For temperature, I have used an encased DS18B20 sensor which I bought five for ten dollars on Amazon. Looks waterproof, but does not do humidity.
@ netcodernaut - Perhaps something like this:
http://www.seeedstudio.com/depot/soil-moisture-temperature-sensor-p-1356.html
@ Duke Nukem - that’s a neat looking sensor. How would that get connected and what code would be used to read the values?
@ DanW
Here’s info for Auduino as a starter: GitHub - practicalarduino/SHT1x: Arduino library to support SHT1x-series (SHT10, SHT11, SHT15) temperature / humidity sensors from Sensirion
My two cents about this matter: the seedstudio sensor doesn’t seem to be up to the job… It carries a Sensirion SHT which is design to measure relative humidity. That works on air not on soil. If you bury it (and this depends heavily on the type of soil!) the sensor will measure the relative humidity of the air contained in the copper net (which can be rather different from the soil water content).
The soil “humidity” is actually the soil water content which can’t be measured with relative humidity sensors.
The gadgeteer sensor and similar “infer” the water content by measuring the change in capacitance around it, which is influenced by the quantity of water that is present in the soil.
Another technology for this purpose is reflectometry in which the sensor generates pulsed energy and analyses what bounces back and then inferring the quantity of water present in it’s surroundings.
Amazon has a couple of pages of soil moisture sensors.
You will likely be disappointed with anything that is inexpensive. I have been sticking sensors in dirt and compost for a few years now. My first attempt was to make my own with DS18B20’s that I soldered myself to regular CAT5 Ethernet cable. Even though I thought that I did adequate moisture protection, they only worked when the soil was dry. Since the data I got indicated I didn’t really need to worry about the soil temperature, I abandoned them in place and ran a new wire and placed the sensor above ground (on the outdoor faucet). It works quite well, but still gets a bad reading every now and then (not enough to cause a problem, since the code ignores bad readings).
For my compost pile, I have been through at least six pre-made stainless steel covered DS18B20s. They last anywhere from a few weeks to a few months. For my next batch, I am going to make a thermowell (probably standard 1/2" copper pipe) and put the sensors in that. I believe the combination of high temp (up to 142F) and moisture are too much for the waterproofing done for the cheap sensors (a few dollars each).
For soil moisture I have been looking at this: Soil Moisture Sensor - VH400
It looks really nice and one of these days I will actually buy one. They claim a very large temperature range (-40 to +85 C). So if you want to bury something for years, this looks like it might be the one to get.
I was also looking at this a couple of years ago. At that stage I quite fancied a New Zealand made one called Aquaflex that is widely used on farms here and in Australia. But if I remember correctly it was also quite expensive.
Here is a quick link I found that describes it : http://www.scottech.net/products/by_supplier/aquaflex_soil_moisture_sensor/