Bluetooth Managed Knowledge Logger Robotic For Soil Testing

saniThis robotic may be managed with a smartphone utilizing Bluetooth by means of an Android app. Its three sensors can measure 4 parameters: temperature, humidity, soil moisture, and ambient mild depth in greenhouses, farms, gardens, parks, and so on.

Often robots like robotic hand, agriculture robotic, fire-fighting robotic, spy robotic, snake robotic, humanoid, bomb (or mine) diffusing robotic function routinely with none human intervention or are remote-controlled. Distant-controlled robots are largely wi-fi.

Block diagram of Bluetooth-controlled data logger robot
Fig. 1: Block diagram of Bluetooth-controlled knowledge logger robotic

There are several types of wi-fi remote-controlled robots like:

  1. Fireplace-fighting robots, that are used as hearth extinguishers for spraying water or cardon-dioxide on hearth.
  2. Bomb (mine) diffusing robots, that are used to diffuse dwell bombs or mines in a battlefield.
  3. Snake robots, which may enter small tunnels or pipelines for search and rescue operations or to seek out out any drawback like leakage in pipelines

This robotic displays the ambient parameters in a subject. The operator can manoeuvre the robotic in a radius of 10 to 30 metres and take measurements to pick the perfect place for plantation. And if plantation is already executed, the above-mentioned 4 parameters may be checked to see whether or not these are inside the threshold ranges or not for taking any corrective actions.

This undertaking may be modified for another functions additionally by simply altering the sensors. For instance, by equipping the robotic with MQ2, MQ3 or comparable fuel sensors, it may be used to detect leakage of any fuel like cardon-dioxide, methane, or LPG.


Earlier than constructing the robotic, allow us to first perceive its working by means of the system block diagram proven in Fig. 1 and the circuit diagram in Fig. 2. The key constructing blocks of the system embrace the three sensors (soil moisture, DHT11 temperature and humidity sensor, and LDR), an Arduino Uno improvement board, Bluetooth module HC-05, DC servo motor, two DC gear motors, and motor driver chip L293D. Allow us to first perceive the function of the foremost elements used within the undertaking.

Circuit diagram
Fig. 2: Circuit diagram

Soil moisture sensor (SM1) is used to measure moisture content material in soil and provides analogue voltage output as per the moisture degree. Its output voltage decreases as moisture content material will increase.

DHT11 temperature and humidity sensor (SM2) is a brilliant sensor that measures atmospheric temperature and humidity and provides direct digital values for temperature in °C and for humidity in % RH.

The sunshine dependant resistor (LDR1) is a photo-conductive gadget whose resistance decreases as mild depth will increase, and vice versa.

Bluetooth module (HC-05) is used to command (to maneuver ahead, reverse, left, and proper) the robotic from a smartphone with the assistance of Arduino Uno microcontroller.

The Arduino Uno board (Board1) performs following duties:

  • Reads analogue output voltage from soil moisture sensor and converts it into digital worth. Then it calibrates it between 0 and 100% moisture degree
  • Reads temperature and humidity values from DHT11 sensor
  • Reads analogue voltage output from LDR1 and calibrates mild depth between 0 and 100%
  • Will get totally different instructions from Bluetooth module and rotates two DC motors to maneuver the robotic ahead, reverse, left, proper, or cease it.
  • Sends (transmits) readings of all three sensors to Android smartphone by means of Bluetooth module

Motor driver L293D (IC1) offers ample voltage and present to each the motors to rotate them. It amplifies the output of Arduino board (Board1) and drives the motors.

The DC motors (M1 and M2) drive left and proper wheels of the robotic and transfer it ahead, backward, left, and proper.

Soil moisture sensor (SM1) is hooked up to servo motor (M3) shaft. This motor strikes the sensor up and right down to insert it into the soil to examine soil moisture content material.

HC-05 module operates on 5V acquired from the Arduino board. It communicates with Arduino board with USART pins Tx (D1) – Rx (D0). So, its Tx pin is linked to Rx pin of Arduino board and vice versa.

DHT11 sensor additionally will get its 5V provide from Arduino board. Its digital output is linked to digital pin D7 of Arduino.

The analogue output of soil moisture sensor (SM1) is linked to analogue enter pin A1 of Arduino board. Its 5V provide additionally comes from Arduino board.

LDR1 is configured in pulled-down mode with 10-kilo-ohm pull-down resistor. Its analogue output is given to analogue enter pin A0 of Arduino board.

Digital pins D8, D9, D10, D11 of Arduino board drive DC motors M1 and M2 utilizing L293D chip. These pins are linked to inputs of L293D, and two motors are linked to output of the chip. Servo motor sign (sig) enter is linked to PWM output pin D6 of Arduino board. The motor will get 5V provide from Arduino board.

The motor provide pin Vss of L293D (pin 8) will get 12V from battery. The Arduino board additionally will get 12V enter at its Vin pin from battery. That’s, Vin pin will get 12V enter and provides 5V output to all different elements.

Circuit and operation

The circuit operation begins when 12V battery is linked to Arduino Uno board and L293D chip. Initially, each motors (M1 and M2) are at relaxation and so the robotic can be at relaxation. The servo motor (M3) is at 0° place and soil moisture sensor is in upward place.

To maneuver the robotic in any path, command is required from smartphone by means of Bluetooth based mostly Android software, known as Bluetooth Terminal HC-05 by mightyIT. To do that, open (begin) Bluetooth Android software in smartphone and seek for HC-05 Bluetooth module. As soon as the cellphone detects HC-05 module, pair it with the smartphone’s Bluetooth app. Enter passkey 1234 or 0000 the primary time to pair with HC-05 module.

Now you possibly can ship instructions from the smartphone to robotic to maneuver utilizing the app. Following instructions given within the desk are used to maneuver the robotic (all these instructions are already set in Android software):

When any of the above instructions is shipped (by sending the character in capital letter), it’s acquired by HC-05 module. The module additional provides this command to Arduino serially by means of its Tx-Rx pins. Arduino will get this command and compares it with set instructions. In the event that they match, the robotic strikes within the desired path.

box 1As soon as robotic is in movement, it retains shifting (inside the vary) till command ‘S’ is shipped to cease it. When robotic stops, it strikes the servo motor by 90° in order that soil moisture sensor can go down into the soil to seize soil moisture worth. On the similar time, it begins studying sensor values from DHT11 and LDR. It reads analogue voltage output from soil moisture sensor and LDR and converts it to the vary of 0-100%. It additionally reads digital values of temperature and humidity from DHT11 sensor.

Robotic transmits all 4 values of those sensors to the smartphone by means of Bluetooth module. It retains transmitting these values each three seconds until it’s stopped by urgent ‘S’ command. When any of the instructions (F,B,R,L) is given, the corresponding servo motor strikes from 90° to 0° and the soil moisture sensor strikes up. The robotic stops transmitting sensor readings and begins shifting. Thus it provides an thought of ambient temperature, humidity, soil moisture, and lightweight depth within the space.

Operation of the circuit is managed by this system embedded in Arduino Uno microcontroller ATMega328.

Software program

This system code (BT_controlled_robot.ino) is written in Arduino programming language. It was examined utilizing Arduino IDE model 1.8.18. Earlier than compiling and importing the code, be sure to embrace the related libraries, similar to DHT_sensor_library-1.4.2 and DHT sensor library model 1.4.3. Throughout testing it was discovered that with out these libraries the code couldn’t be compiled.

Obtain Supply Code

Development and testing

The circuit may be assembled on a breadboard or general-purpose PCB. The writer’s prototype is proven in Fig. 3. On connecting the circuit to a 12V DC provide, the onboard LED on Bluetooth HC-05 will begin blinking at a quick charge. While you pair it efficiently together with your Bluetooth app in your cell phone, the LED will blink at a slower charge (two blinks per second). Open the Bluetooth Terminal HC-05 app from the cell phone, choose HC-05 once more.

Author’s prototype
Fig. 3: Writer’s prototype

If every little thing’s positive, you possibly can enter management instructions (F,B,R,L) within the app to maneuver the robotic. On coming into ‘S’ command, the robotic will cease and all of the sensor knowledge may be seen in your cell phone, as proven in Fig. 4.

Various sensors’ data captured on mobile phone
Fig. 4: Numerous sensors’ knowledge captured on cell phone

Soil moisture sensor SM1 must be correctly mounted to the servo arm/horn utilizing both glue gun or screws. When servo motor pulls out soil moisture sensor from the soil, you possibly can see the moisture degree drastically reduces to five, as proven in Fig. 5, indicating that the sensor is out of the soil.

Dry soil status
Fig. 5: Dry soil standing

Ashutosh M. Bhatt is M.Tech in embedded programs. At present, he’s lecturer of electronics and radio engineering at Authorities Polytechnic, Jamnagar, Gujarat

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