Arduino Based 4-in-1 Data Logger System

In greenhouse farming, it is required to monitor, control and maintain four parameters

1.   Temperature
2.   Humidity
3.   Soil moisture
4.   Ambient light

In such farms, these four parameters are continuously monitored and controlled. Maximum efforts are done to maintain required temperature, humidity, soil moisture and light to get good quality of agriculture product.

Several sensors are placed at different places in all over the greenhouse farm and their readings are monitored. If there reading is less than or more than the required level then proper actuators are activated. E.g. if at some place soil moisture level is less, the particular water valve is opened and the pump is turned ON to increase moisture level.

The given project demonstrates how to measure all these four parameters and monitor them continuously. It uses smart sensors like DHT11 to measure temperature and humidity, soil moisture sensor, and LDR to measure ambient light. It uses Arduino to measure all these four parameters and LCD to display their values.

Fig. 1: Prototype of Arduino Based 4-in-1 Data Logger

First, let us see the circuit diagram followed by its description and working.

Circuit description:

As shown in above figure 3 different sensors, soil moisture, LDR, and temperature cum humidity sensor DHT11 are connected to arduino along with one LCD

• The soil moisture sensor has 3 pins, Vcc, Gnd and analog output. Vcc pin is connected to 5 V and Gnd pin is connected to Gnd of arduino board. The analog output is connected to analog input pin A1

• LDR is connected in pulled down configuration. It is pulled down using 10 K resistor. It is also given 5 V from board and its output is connected to analog input pin A0 of arduino board

• DHT11 sensor has also 3 pins Vcc, Gnd and digital output. Its Vcc and Gnd pins are given supply from arduino board while output pins is connected to digital pin 7 of arduino board

• Data pins D4-D7 of LCD are connected to arduino pins 10 – 13. Two control pins Rs and En are connected to pins 8 and 9 respectively. Control pins RW and VEE (contras control) are connected to ground

• Backlight LED of LCD is given 5V supply

Circuit operation:

• DHT11 is a smart digital sensor. It senses temperature and humidity and gives direct value of room temperature in centigrade (and even in Fahrenheit) humidity in % RH

• This direct digital value is read by arduino and displayed on LCD as temperature in oC and humidity in % RH

• As the light intensity changes the LDR resistance changes. So its analog output voltage changes. This analog output is directly proportional to light intensity. So arduino reads this analog voltage and convert it into corresponding digital value using its internal ADC

• The internal ADC of arduino has a 10-bit resolution so its digital output varies from 0 to 1023 as analog input varies from 0 to 5V. This digital output is further converted into 0 to 100% to get light intensity in %

• The soil moisture sensor works on the principle of conductivity. When senses moisture its conductivity increases and vice versa. Its analog output is inversely proportional to soil moisture or conductivity. Means when there is no conductivity or moisture its analog output is maximum – means 5 V

• Again this analog output is read by arduino and converted into digital value. We get the value between 0 to 1023 and it is also converted into 0 to 100 to get soil moisture value in %

• All four sensor values are also sent to PC/laptop through serial port using USB cable for logging the data
Here are snaps of the circuit arrangement.