INTRODUCTION
Hydroponics is a technique to cultivate the plant without
using soil as a growth medium [1]. This technique supplies the
nutrient needed by plant through the water solution. There are
many types of hydroponics technique such as deep water
culture, aeroponic system, drip system, EBB and flow (food
and drink) system, N.F.T (nutrient film technique) and wick
system [2]. Deep water culture (DWC) is one of the
hydroponic system techniques that prepare the nutrient in water
solution into the plant [3]. This technique will ensure the root
of plant will absorb the nutrient in water solution to grow
wisely [4]. By using this technique, there are several
environmental factors that should be considered such as
oxygenation, salinity, pH and conductivity of nutrient solution,
light intensity temperature, photoperiod and air humidity [5].
There are two variables must be considered when growing the
plant in nutrient solution, which is electrical conductivity (EC),
potential of hydrogen ion (pH) [6].
Based on S. Nakoaka and A. Yamada in their research, they
state the changing of pH level will affect to the photosynthetic
activity of plants, due to CO2 is readily soluble in water and
decreases the pH [7]. The maximal growth of plant can be
achieved by increasing it capacity [8]. Since the pH value can
give effect to the photosynthetic activity of plant, the pH level
in water solution should be controlled to avoid the plant will be
damaged. However, the DWC technique is not equipped with
an automatic system that able to maintain the pH level in water
solution, and the user need to adjust the pH level in water
solution manually [9]. Therefore, this research was conducted
to design a system that could maintain the pH level in water
solution for DWC system, which could decrease and increase
the pH level in water solution automatically. In order to make
the system operate automatically, a microcontroller that can
control the operation is required in this system. There are many
types of microcontroller can be used in this project such as PIC
controller, PLC controller and Arduino microcontroller [10,
11].
However, this project uses the Arduino mega 2560
microcontroller to control all of operation systems and to make
the system automatically operate. This type was chosen
because it used the low-power supply (7-12V DC) and used the
simple C++ programming language to program it [12, 13]. This
system also was equipped with the sensor to measure the pH
level in water solution and transferred the compatible signal to
microcontroller to process and provided an output signal to the
actuator (valve) to drop the pH adjuster solution if required.
This system can provide benefits to the production
development for being more accurate, better control, high
safety and reduce of manpower