As my projects evolved in my mind there comes a time to make the ideas come true and so the project below became reality. Its an Arduino based soil moisture sensor, with 16,x2 LCD, real time clock (which keeps time even if the power supply is disconnected), temperature sensor and SD data logger.
It can be very helpful with a bachelor's degree or master's degree biotechnology/biology/botanics/plant keeping projects.
The idea of the project is to build a moisture sensor, both portable and stationary (with 9V battery or supplied with a standard adjustable charger). Its going to take very short measurments every X miliseconds, depending from how you will set it. Why the measurments need to be short? Becouse there is a problem which need to be solved and got solved in an article:
http://www.instructables.com/id/Have-a-Bumper-Crop... ----- By: Robert M / ArduinomasteR
who improved my first instructable which im very grateful for:
http://www.instructables.com/id/Arduino-LCD-Soil-M... ----- By: Wojciech Marczak / WojciechM3
Those two articles became the base for my idea, how to improve it and make it even better
So the idea to make the probes last longer is to let the current only flow in a short time (2x 30 miliseconds in our case) and to turn it off for a set amount of time, for example 1,800,000 milisecounds = (30x60x1000) = 30 minutes. To set this value you need to change the delay at the very end of a project.ino file.
However, since we have the sensor which takes the measurements every X miliseconds, now we need map the values. The values will vary from 1000 and something about stable 400, However the lower the measurment the lesser is the resistance, and since the probes check the resistance between two bolts we need to make Value of 400 or similar to be humidity 100% and a bigger resistance, 1000 or above means the humidity is 0% So we need to map the values of 1000 --> 400 to be humidity 0 ---> 100%
All of those things will be done in the next steps of this instructable.