Design and Development of Solar Powered Grain Dryer for Storage - A PROJECT

 

CHAPTER-1

INTRODUCTION

 

            India being a predominately agricultural based country, where  70% of the population are farmers and practice agriculture for a living technological advancement should improvise in order to reduce the workload of a farmer and make their work more mechanized and easy .

 

            Agriculture serves to be the backbone of Indian economy. It is very important to improve the efficiency and productivity of agriculture by simultaneously providing safe cultivation to the farmers. Drying is the process of removing the moisture content from the grains of the crops after they have been harvested, after harvesting grains usually contain about 25 to 30% moisture content which is not ideal to store them as they may lead to discoloration, spoilage, encourage development of molds, and increase the likelihood of attack from pests. It may lead to a decrease in the germination rate in case of rice seed. Hence, it is important to dry grains as soon as possible after harvesting-ideally within 24 hours. Delays in drying, incomplete drying or ineffective drying will reduce grain quality and result in losses.

 

            There are plenty of applications using automatic grain dryers. The crops can be harvested at any time of the year and be stored for a long period of time. Drying the grains to the optimum value of moisture content will increase the shelf life of the grain tremendously. The burden and work load on the farmers will be reduced drastically and they can utilize this time elsewhere. Using an automated system of drying, the drying process can be completed within a few hours. Paddy contains about 25-30% of moisture content after it has been harvest. To preserve/store them for a longer time, they need to be dried to 14% of moisture. It also reduces harvesting losses, including head shattering and cracked kernels. Further it helps in reducing the dependency on weather conditions for harvest and drying. Which in turn allows the farmer to spend more time on other activities post harvest.

CHAPTER-2

LITERATURE REVIEW

 

Natural Convection Solar Dryer of Box Type:

By ” Amin Omda Mohamed Akoy et al.’’

            This paper presents the description of natural convection solar dryer of a box- type (cabinet) was designed and constructed.  The constructed dryer consisted of drying chamber and solar collector combined in one unit as shown in Figure.2.1.and they concluded the designed dryer with a solar collector area of 16.8 m² is expected to dry 195.2 kg fresh mango (100kg of sliced mango) from initial moisture 81.4% to 10% final moisture in two days under ambient conditions during harvesting period from April to June. 

 

Figure.2.1 Isometric view of constructed solar  dryer.

 

            A prototype of the dryer with 1.03m² solar collector  area was constructed to be used in experimental drying  tests. The average ambient conditions are 30ºC air  temperature and 15% relative humidity and air flow  rate 0.0903 kg/s with daily global solar radiation  incident on the horizontal surface of about 232 W/m² for  drying time 10 hours per day.

 

Solar dryer with thermal energy storage for intermittent drying of cocoa beans:

By‘’ Fagunwa et.al”

            This paper presents the description of solar dryer with thermal energy storage for intermittent drying of cocoa beans as shown in figure.2.2. Drying mechanism was based on a combination of convective heating and direct radiation, with a provision for controlling the rate of air flow through the beans. The solar collector area is basically a top open wooden box, 1100 x 1000 x 200 mm made from 10mm thick  plywood. The experimental model dehydrated cocoa beans from 53.4 to 3.6% moisture content (w.b) in a 72 hours intermittent drying process against ambient temperature and relative humidity in the range 25-30°C and 58-98%, respectively. Free convective drying attained equilibrium moisture content of 3.56% (w.b); whilst, 9.09% and 7.11% (w.b) were obtained with the  forced convective drying, with 1.02 and 1.32 m3/min  airflow rates, respectively.

Figure.2.2 Schematic illustration showing plan  view and elevation of the experimental solar dryer

 

Hybrid solar dryer using direct solar energy and heat exchanger:

By “ M.A. Amer et.al ”

            This paper presents the description of hybrid solar  dryer designed and constructed using direct solar energy and a heat exchanger as shown in fig.2.3.The efficiency of the solar dryer was raised by  recycling up to 65% of the drying air in the solar dryer  and exhausting a small amount of it outside the dryer.

            Under Mid-European summer conditions it can raise up  the air temperature from 30 to 40ºC above the ambient  temperature. The capacity of the dryer was to dry about  30 kg of banana slices in 8 h in sunny day from an  initial moisture content of 82% to the final moisture  content of 18% (wb).In the same time it reduced to only  62% (wb) moisture content in open sun drying method. 

 

Figure.2.3 Schematic diagram of solar hybrid dryer

CHAPTER-3

PROBLEM STATEMENT

 

            The purpose of storage is to provide the dried grain with protection against insects, molds, rodents and birds, and to prevent moisture from re-entering the grain. But, if the drying is not done properly, there will be losses no matter how good the storage is.

 

            Technological advancements have brought about a lot of changes in our day to day life and we have been immensely grateful for that. Similarly, the agricultural sector has been growing everyday either in its production or in the technological aspect. Time has always been the greatest enemy and shortage of time has led to many problems faced by every individual on this planet. In order to reduce the time of the farmer postharvest, the proposed idea is being implemented. The motor controlled conveyor belts made out of netted material are perfect in order to lay the grains conveniently and also for the proper penetration of hot air. It uses an Arduino Uno Microcontroller for the smart controlling action which needs to be implemented for the drying process. Natural sun drying technique would use the heat from the sun rays to dry the grains for a period of 10-15 days, which gets very tedious and monotonous. Making use of the same principle, in this report it uses the heat generated from a heating coil along with the exhaust fan, which thereby produces heat required to dry the grains as per the specifications and standard which is desired.

 

Problem Definition:

            The purpose of storage is to provide the dried grain with protection against insects, molds, rodents and birds, and to prevent moisture from re-entering the grain. But, if the drying is not done properly, there will be losses no matter how good the storage is.

 

            Technological advancements have brought about a lot of changes in our day to day life and we have been immensely grateful for that. Similarly, the agricultural sector has been growing everyday either in its production or in the technological aspect.

            Time has always been the greatest enemy and shortage of time has led to many problems faced by every individual on this planet. In order to reduce the time of the farmer postharvest, the proposed idea is been implemented. The motor controlled conveyer belts made out of netted material is perfect in order to lay the grains conveniently and also for the proper penetration of hot air. It uses an Arduino Uno Microcontroller for the smart controlling action which needs to be implemented for the drying process.

 

            Natural sun drying technique would use the heat from the sun rays to dry the grains for a period of 10-15 days, which gets very tedious and monotonous. Making use of the same principle, in this paper it use the heat generated from a heating coil along with the exhaust fan, which thereby produces heat required to dry the grains as per the specifications and standard which is desire to.

 

Objective of the System:

            The main objective of this paper is to make the work of farmers easy, faster and high efficient in grain drying, postharvest for storage. The designed mechanism takes less time to dry up grain using solar photovoltaic based drying as compared to traditional drying process. It also aims to reduce intensive labor experienced by the farmers.

 

            The components used to solve the problem includes the following: solar panel, buck boost converter, charge controller circuit, Johnson DC geared motor (10rpm), Arduino Uno, temperature and humidity sensor (DHT11), moisture sensor, 5V dual channel relay, L298N H Bridge motor driver circuit, heating elements, DC fans, Conveyer belts, bread board and jumper wires.

CHAPTER-4

OBJECTIVES

 

 

• Automatic grain dryers show that the farmers can be at ease and the drying process is completed within a few hours.

 

• The designed system uses a conveyor belt system on which the grain will be layered evenly and dried thoroughly with the help of a heating coil and fan attached above the conveyor belt.

 

• Proposed system is very less as all the components used are very cost effective.

 

• The developed system can be used to dry grains such as wheat, paddy, lentils, ragi, millets, corn and coffee.

CHAPTER-5

METHODOLOGY

 

            Methodology of design and development of solar powerered grain dryer methodology. Designing and developing a solar-powered grain dryer involves several steps and considerations. Below is a general methodology to guide you through the process:

 

Project Planning and Research:

            Clearly define the project objectives: Determine the capacity of the grain dryer, the types of grains to be dried, and the target drying time. Research existing solar-powered grain dryers: Study existing designs and technologies to understand their strengths and weaknesses. Learn from previous experiences to improve your own design.

 

Site Assessment:

Identify the location: Choose a suitable site with ample sunlight exposure throughout the year.

Assess the solar resource: Gather solar radiation data for the location to estimate the available energy for the system.

Analyze the grain production and consumption: Understand the grain production cycles and the amount of grain that needs drying to size the dryer appropriately.

 

System Design:

Heat Source: Determine the heat source for the dryer. It could be air-based or direct-heating, and it may involve using solar collectors to concentrate sunlight or using photovoltaic panels to generate electricity for electric heaters.

Airflow System: Design an efficient airflow system to ensure uniform drying and minimize drying time.

Temperature and Humidity Control: Incorporate temperature and humidity sensors to control the drying process effectively.

Insulation: Consider proper insulation to reduce heat losses during the drying process.

 

Component Selection:

Solar Panels: Choose high-efficiency photovoltaic panels to capture maximum solar energy.

Energy Storage (optional): If required, select appropriate battery systems to store excess energy for use during cloudy days or at night.

Fans/blowers: Choose efficient fans or blowers to ensure proper airflow through the grain dryer.

 

Prototype Development:

Build a small-scale prototype: Develop a working prototype to test and validate your design concepts. This step will help you identify and resolve potential issues early on.

 

Testing and Optimization:

            Test the prototype under various weather conditions and different grain types to optimize its performance. Collect data on drying times, energy consumption, and grain quality to make improvements as needed.

 

Safety and Efficiency Considerations:

            Ensure that the dryer is safe to operate and complies with all relevant safety standards. Design the system for maximum energy efficiency to minimize operating costs.

 

CHAPTER-6

WORKING PRINCIPLE

 

            The main objective of this is to make the work of farmers easy, faster and high efficient in grain drying, postharvest for storage. The designed mechanism takes less time to dry up grain using solar photovoltaic based drying as compared to traditional drying process. It also aims to reduce intensive labor experienced by the farmers. The components used to solve the problem includes the following: solar panel, buck boost converter, charge controller circuit, Johnson DC geared motor (10rpm), Arduino Uno, temperature and humidity sensor (DHT11), moisture sensor, 5V dual channel relay, L298N H Bridge motor driver circuit, heating elements, DC fans, Conveyor belts, breadboard and jumper wires.

 

Functional Block Diagram:

            A simple, solar powered automatic grain dryer is designed to dry the grains effectively and in a fast manner. The dryer has a simplistic architecture which makes assembling and disassembling the parts easier. The functional block diagram of the dryer is shown in Figure 5.1. Working of each block is explained in this section. The power circuit system comprises solar panel, controller, battery charging circuit and battery. The Solar Panel will provide electricity to charge the battery during day time, which in turn is used to power the system. The charging of the battery is controlled by a solar charge controller.

Block Diagram:

Fig 6.1. Block diagram.

Control Circuit Working:

         From the battery, the voltage is stepped down to 5 V using buck converter and is then given to the Arduino and DC motors as power supply. The conveyor belt is made to rotate at a very low rpm of 10, which is achieved by the Johnson DC geared motor.

 

            The Arduino is the main microcontroller used in dryer, the dryer system contains temperature and humidity sensor (DHT11) to sense the temperature of the heating chamber, moisture sensor(FC-28) to check the moisture contact presenter in the grains, heating coil to make the chamber hot, DC Fans push the hot air onto the conveyor belts, L298N H bridge motor driver circuit to control the speed of the DC geared motors.

 

            The Inputs to the Arduino are given by all the 3 sensors namely temperature and humidity Sensor (DHT11), moisture sensor(FC-28) 2 in number.

 

Temperature Sensor Control Working :

            The temperature sensor senses the temperature of the heating inside the heating chamber, keeping a range of allowable temperatures of the heating chamber, which is 35’ C to 42’ C the exhaust fans are designed to run only in this range of allowable temperature which helps to blow the hot air on to the conveyor belts.

            The dual channel relay module will cut the power supply to the DC fans when the temperature detected is out of the range.

 

Moisture Sensor Control Working:

            Another input to the Arduino uno is the moisture sensor which detects the moisture from the wet harvested grains which are evenly layered on the conveyor belts. Post-harvest grains usually contain a moisture content of about 25-30%, which is not the ideal moisture content to store these grains. Therefore, after drying the grains using a dryer, the moisture content comes down to 12-14%, which is ideally enough to store these grains for a period of 6-12 months.

 

EXPERIMENTAL SETUP

            The hardware structure is designed as shown in Figure 4.2, the conveyor belts are made using netted material to provide flexibility and holes to penetrate the air through the grains and conveyor belt. Arduino Uno is coded based on the requirements and connections to various components. The detailed explanation about the experimental setup of the dryer is explained in this section.

 

A. Interfacing of Arduino Uno , Temperature & humidity sensor (DHT11), relay and DC fans:

            Pin A0 of Arduino is connected to the data pin of the DHT11 temperature and humidity sensor, VCC and GND pins are given to the supply. The relay module is connected to the A1 and A2 pins of the Arduino and the DC fans are connected internally to the relay so provide the switching actions.

 

B. Heating Coil Control

            To regulate the speed of the fan, the temperature sensor (DHT11) and moisture sensor are defined as inputs to the Arduino Uno at pin number A0 and A1 respectively. Taking in the temperature and moisture values, the Arduino thus defines a control strategy. It is a crucial step to control the speed of the fan and the heating coil temperature as it may over dry the grains or under dry them resulting in a loss and spoilage of grains . After a lot of trials and errors, the temperature value was set accordingly and considering the fact the moisture content in the grains should be in the range of 12-14 %, these values are predefined and set.

C. Interfacing of Arduino uno, Moisture sensor, L298N H bridge motor driver IC :

            Pin A2 of the Arduino board is connected to the data pin of the moisture sensor, VCC and GND pins are given to the supply. The L298N H Bridge motor driver IC is connected to the pins 8, 9 and 10 of the Arduino, and the motor is internally supplied and connected to the L298N motor driver IC.

 

D. Motor Driver and Moisture Content Control

            In order to regulate the speed of the conveyor belt motor, the moisture sensor value is the key parameter which gives input to the Arduino Uno. As stated in the introduction, the moisture content which is ideal for storing the grains for a period of 6-12 months is about 12 - 14%, thereby the band range for the moisture content of the grains in the program is 12 - 14%. The speed of the motor is controlled as follows: If the moisture content of the grains is lesser than 15%, the Johnson DC motor runs at half its speed of 5 rpm. If the moisture content of the grains is greater than 11%, the Johnson DC motor runs at full speed of 10rpm.

 

            The entire control circuitry is interfaced and placed on a suitable platform and attached to the top right corner of the outer enclosure model of the model. There are two Arduino Uno's used to control the entire circuit as the number of analog input output pins were not sufficient to connect all the sensors, relays and motor driver circuits into a single Arduino Uno. The connections to Arduino Uno–1 comes from the moisture sensor-2 and the L298N motor driver IC and breadboard, these connections form the motor driver control circuitry along with the moisture sensor. The connections to Arduino Uno–2 comes from the moisture sensor-1, temperature and humidity sensor (DHT11), and 5V dual channel relay module and bread board. These connections form the heating coil control circuitry

COMPONENT EXPLANATION

 

Arduino UNO Overview

            The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.

 

            The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega16U2 (Atmega8U2 up to version R2) programmed as a USB-to-serial converter. Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode. Revision 3 of the board has the following new features:

1.0 pinout: Added SDA and SCL pins that are near to the AREF pin and two other new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board. In future, shields will be compatible both with the board that uses the AVR, which operates with 5V and with the Arduino Due that operate with 3.3V. The second one is a not connected pin that is reserved for future purposes.

Fig.6.1 (a) Arduino UNO

Microcontroller                       :           ATmega328

Operating Voltage                  :           5V

Input Voltage                          :           (recommended) 7-12V

Input Voltage                          :           (limits) 6-20V

Digital I/O Pins                       :           14 (of which 6 provide PWM output)

Analog Input                           :           Pins 6

DC Current per I/O Pin          :           40 mA

DC Current for 3.3V Pin        :           50 mA

Flash Memory                         :           32 KB of which 0.5 KB used by bootloader

SRAM                                     :           2 KB

EEPROM                                :           1 KB

Clock Speed                            :           16 MHz

 

 

Fig.6.1(b) Overview of ARDUINO UNO

Power

• The Arduino Uno can be powered via the USB connection or with an external power supply. The power source is selected automatically.
• External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector.
• The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

 

The power pins are as follows:

VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

 

5V.This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

 

3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.

GND. Ground pins.

 

Memory

            The ATmega328 has 32 KB (with 0.5 KB used for the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

Input and Output

            Each of the 14 digital pins on the Uno can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions:

 

Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip.

 

External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attach-interrupt() function for details.

 

PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogWrite() function.

 

SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library.

 

LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off.

 

            The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and the analog reference() function. Additionally, some pins have specialized functionality:

 

TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire library.

 

There are a couple of other pins on the board:

• AREF. Reference voltage for the analog inputs. Used with analogReference().
• Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

            See also the mapping between Arduino pins and ATmega328 ports. The mapping for the Atmega8, 168, and 328 is identical.

 

Communication

            The Arduino Uno has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega16U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '16U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. The Arduino software includes a serial monitor which allows simple textual data to be sent to and from the Arduino board. The RX and TX LEDs on the board will flash when data is being transmitted via the USB-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

 

            A SoftwareSerial library allows for serial communication on any of the Uno's digital pins.  The ATmega328 also supports I2C (TWI) and SPI communication. The Arduino software includes a Wire library to simplify use of the I2C bus; see the documentation for details. For SPI communication, use the SPI library.

 

Programming

            The Arduino Uno can be programmed with the Arduino software (download). Select "Arduino Uno from the Tools > Board menu (according to the microcontroller on your board).

 

            The ATmega328 on the Arduino Uno comes pre-burned with a bootloader that allows you to upload new code to it without the use of an external hardware programmer. It communicates using the original STK500 protocol ( C header files).

            You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header.

 

            The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code is available. The ATmega16U2/8U2 is loaded with a DFU bootloader, which can be activated by:

 

            On Rev1 boards: connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2.

 

            On Rev2 or later boards: there is a resistor that pulls the 8U2/16U2 HWB line to ground, making it easier to put into DFU mode.

 

            You can then use Atmel's FLIP software (Windows) or the DFU programmer (Mac OS X and Linux) to load a new firmware. Or you can use the ISP header with an external programmer (overwriting the DFU bootloader).

 

Automatic (Software) Reset

            Rather than requiring a physical press of the reset button before an upload, the Arduino Uno is designed in a way that allows it to be reset by software running on a connected computer. One of the hardware flow control lines (DTR) of the ATmega8U2/16U2 is connected to the reset line of the ATmega328 via a 100 nanofarad capacitor. When this line is asserted (taken low), the reset line drops long enough to reset the chip. The Arduino software uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. This means that the bootloader can have a shorter timeout, as the lowering of DTR can be well-coordinated with the start of the upload.

 

            This setup has other implications. When the Uno is connected to either a computer running Mac OS X or Linux, it resets each time a connection is made to it from software (via USB). For the following half-second or so, the bootloader is running on the Uno. While it is programmed to ignore malformed data (i.e. anything besides an upload of new code), it will intercept the first few bytes of data sent to the board after a connection is opened.

            If a sketch running on the board receives one-time configuration or other data when it first starts, make sure that the software with which it communicates waits a second after opening the connection and before sending this data.

 

            The Uno contains a trace that can be cut to disable the auto-reset. The pads on either side of the trace can be soldered together to re-enable it. It's labeled "RESET-EN". You may also be able to disable the auto-reset by connecting a 110 ohm resistor from 5V to the reset line; see this forum thread for details.

 

USB Overcurrent Protection

            The Arduino Uno has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port, the fuse will automatically break the connection until the short or overload is removed.

 

DHT11 Temperature and Humidity Sensor

            DHT11 is a part of DHTXX series of Humidity sensors. The other sensor in this series is DHT22. Both these sensors are Relative Humidity (RH) Sensor. As a result, they will measure both the humidity and temperature. Although DHT11 Humidity Sensors are cheap and slow, they are very popular among hobbyists and beginners.

Fig 6.2(a).DHT11 Temperature and humidity sensor

 

            The DHT11 Humidity and Temperature Sensor consists of 3 main components. A resistive type humidity sensor, an NTC (negative temperature coefficient) thermistor (to measure the temperature) and an 8-bit microcontroller, which converts the analog signals from both the sensors and sends out a single digital signal. This digital signal can be read by any microcontroller or microprocessor for further analysis.

Fig 6.2(b).DHT11 pin representation

 

DHT11 Humidity Sensor consists of 4 pins: VCC, Data Out, Not Connected (NC) and GND. The range of voltage for VCC pin is 3.5V to 5.5V. A 5V supply would do fine. The data from the Data Out pin is a serial digital data.

 

            The fig.4.2(c) shows a typical application circuit for DHT11 Humidity and Temperature Sensor. DHT11 Sensor can measure a humidity value in the range of 20 – 90% of Relative Humidity (RH) and a temperature in the range of 0 – 500C. The sampling period of the sensor is 1 second i.e.

Fig.6.2©Application circuit

            All the DHT11 Sensors are accurately calibrated in the laboratory and the results are stored in the memory. A single wire communication can be established between any microcontroller like Arduino and the DHT11 Sensor.

 

            Also, the length of the cable can be as long as 20 meters. The data from the sensor consists of integral and decimal parts for both Relative Humidity (RH) and temperature.

 

L293D IC (DC MOTOR DRIVER):

FIG.6.3(a): L293 & L293D Driver ICs

 

            The L293 and L293D are quadruple high-current half-H drivers. The L293 is designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to 36 V. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. Both devices are designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications. All inputs are TTL compatible. Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN.

 

            When an enabled input is high, the associated drivers are enabled and their outputs are active and in phase with their inputs. When the enable input is low, those drivers are disabled and their outputs are off and in the high-impedance state.

            With the proper data inputs, each pair of drivers forms a full-H (or bridge) reversible drive suitable for solenoid or motor applications. On the L293, external high-speed output clamp diodes should be used for inductive transient suppression. A VCC1 terminal, separate from VCC2, is provided for the logic inputs to minimize device power dissipation. The L293and L293D are characterized for operation from 0°C to 70°C.

Fig.6.3(b). Control of DC motors with an H-bridge IC

Fig.6.3. (c) Truth table and description of L293D IC with DC motor

DC Gear Motor Working:

            Geared DC motors can be defined as an extension of DC motor which already had its Insight details demystified here. A geared DC Motor has a gear assembly attached to the motor. The speed of the motor is counted in terms of rotations of the shaft per minute and is termed as RPM .The gear assembly helps in increasing the torque and reducing the speed. Using the correct combination of gears in a gear motor, its speed can be reduced to any desirable figure. This concept where gears reduce the speed of the vehicle but increase its torque is known as gear reduction.  This Insight will explore all the minor and major details that make the gear head and hence the working of geared DC motors.

 

External Structure

            At the first sight, the external structure of a DC geared motor looks as a straight expansion over the simple DC ones.

 

        The lateral view of the motor shows the outer protrudes of the gear head. A nut is placed near the shaft which helps in mounting the motor to the other parts of the assembly.

Fig.6.3.(d).Lateral view of DC Geared motor.

 

            Also, an internally threaded hole is there on the shaft to allow attachments or extensions such as wheels to be attached to the motor.

 

Outer Body of Gear Head & Rear View

            The outer body of the gear head is made of high density plastic but it is quite easy to open as only screws are used to attach the outer and the inner structure. The major reason behind this could be to lubricate the gear head from time to time.

 

            The plastic body has a threading through which nut can be easily mounted and vice versa from the gear head.

Fig.6.3.(e).Outer body of DC Gear Head

 

Rear View

            The rear view of the geared motor is similar to the DC motor and it has two wires soldered to it.

Fig.6.3.(f).Rear view of DC Gear Head.

Internal Structure

            On opening the outer plastic casing of the gear head, gear assemblies on the top as well as on the bottom part of the gear head are visible. These gear assemblies are highly lubricated with grease so as to avoid any sort of wear and tear due to frictional forces. Shown below is the top part of the gear head. It is connected to a rotating shaft and has one gear that allows the rotation. A strong circular imprint shows the presence of the gear that rotates the gear at the upper portion.

Bottom Gear Assembly

            A closer look at the bottom gear assembly shows the structure and connection with other gears.

Fig.6.3(h).Internal structure of DC Gear motor.

 

            Gear assembly’s association with the motor (bottom gear assembly) can be understood with the help of the image shown below.

Fig.6.3.(I).Bottom Gear assembly.

 

            The gear assembly is set up on two metallic cylinders whose working can be called as similar to that of an axle. A total of three gears combine on these two cylinders to form the bottom gear assembly out of which two gears share the same axle while one gear comes in between them and takes a separate axle.

 

        The gears are basically in form of a small sprocket but since they are not connected by a chain, they can be termed as duplex gears in terms of a second cog arrangement coaxially over the base. Among the three gears, two are exactly the same while the third one is bigger in terms of the number of teeth at the upper layer of the duplex gear. The third gear is connected to the gear at the upper portion of the gear head. 

Working

Working of the DC Geared Motor

            The DC motor works over a fair range of voltage. The higher the input voltage more is the RPM (rotations per minute) of the motor. For example, if the motor works in the range of 6-12V, it will have the least RPM at 6V and maximum at 12 V.

In terms of voltage, we can put the equation as:

RPM =  K1 * V, where,

K1  =  induced voltage constant

V   =  voltage applied

Fig.6.3(j).DC Geared motor.

 

            The working of the gears is very interesting to know. It can be explained by the principle of conservation of angular momentum. The gear having smaller radius will cover more RPM than the one with larger radius. However, the larger gear will give more torque to the smaller gear than vice versa. The comparison of angular velocity between input gear (the one that transfers energy) to output gear gives the gear ratio. When multiple gears are connected together, conservation of energy is also followed.  The direction in which the other gear rotates is always the opposite of the gear adjacent to it.

 

            In any DC motor, RPM and torque are inversely proportional. Hence the gear having more torque will provide a lesser RPM and converse. In a geared DC motor, the concept of pulse width modulation is applied.  The equations detailing the working and torque transfer of gears are shown below:

 

 

            In a geared DC motor, the gear connecting the motor and the gearhead is quite small, hence it transfers more speed to the larger teeth part of the gear head and makes it rotate. The larger part of the gear further turns the smaller duplex part. The small duplex part receives the torque but not the speed from its predecessor which it transfers to larger parts of other gear and so on. The third gear’s duplex part has more teeth than others and hence it transfers more torque to the gear that is connected to the shaft.  

 

2 X 16 LCD DISPLAYS:

            Liquid crystal display (LCD) has material which joins together the properties of both liquid and crystals. They have a temperature range within which the particles are essentially as mobile as they might be in a liquid, however are gathered together in an order form similar to a crystal.

 

            The LCD is much more informative output device than a single LED. The LCD is a display that can easily show characters on its screen. They have a couple of lines to large displays. Some LCDs are specially designed for specific applications to display graphic images. 16×2 LCD (HD44780) module is commonly used. These modules are replacing 7-segments and other multi-segment LEDs. LCD can be easily interfaced with microcontroller to display a message or status of the device. It can be operated in two modes: 4-bit mode and 8-bit mode. This LCD has two registers namely command register and data register. It is having three selection lines and 8 data lines. By connecting the three selection lines and data lines with the microcontroller, the messages can be displayed on LCD.

 

 

 

16X2 LCD pinout diagram

 

LCD interfacing with Microcontrollers-4bit mode

            In 4-bit mode the data is sent in nibbles, first we send the higher nibble and then the lower nibble. To enable the 4-bit mode of LCD, we need to follow special sequence of initialization that tells the LCD controller that user has selected 4-bit mode of operation. We call this special sequence as resetting the LCD. Following is the reset sequence of LCD.

• Wait for about 20mS
• Send the first init value (0x30)
• Wait for about 10mS
• Send second init value (0x30)
• Wait for about 1mS
• Send third init value (0x30)
• Wait for 1mS
• Select bus width (0x30 - for 8-bit and 0x20 for 4-bit)
• Wait for 1mS

            The busy flag will only be valid after the above reset sequence. Usually we do not use busy flag in 4-bit mode as we have to write code for reading two nibbles from the LCD. Instead we simply put a certain amount of delay usually 300 to 600uS. This delay might vary depending on the LCD you are using, as you might have a different crystal frequency on which LCD controller is running. So it actually depends on the LCD module you are using. So if you feel any problem running the LCD, simply try to increase the delay. This usually works.

 

LCD connections in 4-bit Mode

            Above is the connection diagram of LCD in 4-bit mode, where we only need 6 pins to interface an LCD. D4-D7 are the data pins connection and Enable and Register select are for LCD control pins. We are not using Read/Write (RW) Pin of the LCD, as we are only writing on the LCD so we have made it grounded permanently. If you want to use it. Then you may connect it on your controller but that will only increase another pin and does not make any big difference. Potentiometer RV1 is used to control the LCD contrast. The unwanted data pins of LCD i.e. D0-D3 are connected to ground.

 

Sealed Maintenance Free Battery:

            Battery  (electricity),  an  array  of  electrochemical  cells  for  electricity  storage,  either individually linked or individually linked and housed in a single unit. An electrical battery is a combination of one or more electrochemical cells, used to convert stored chemical energy into electrical energy. Batteries may be used once and discarded, or recharged for years as in standby power applications. Miniature cells are used to power devices such as hearing aids and wristwatches; larger batteries provide standby power for telephone exchanges or computer data centers.

Figure.6.4: SMF Battery

PV CELLS WORK:

Fig.6.5(a).PV cells

            A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped (N-type) silicon on top of a thicker layer of boron doped (P-type) silicon. An electrical field is created near the top surface of the cell where these two materials are in contact, called the P-N junction. Since the top of the cell must be open to sunlight, a thin grid of metal is applied to the top instead of a continuous layer. The grid must be thin enough to admit adequate amounts of sunlight, but wide enough to carry adequate amounts of electrical energy.

Fig.6.5(b).working of PV Cells.

            Light, including sunlight, is sometimes described as particles called "photons." As sunlight strikes a photovoltaic cell, photons move into the cell. When a photon strikes an electron, it dislodges it, leaving an empty "hole". The loose electron moves toward the top layer of the cell. As photons continue to enter the cell, electrons continue to be dislodged and move upwards. If an electrical path exists outside the cell between the top grid and the backplane of the cell, a flow of electrons begins. Loose electrons move out the top of the cell and into the external electrical circuit. Electrons from further back in the circuit move up to fill the empty electron holes. Most cells produce a voltage of about one-half volt, regardless of the surface area of the cell. However, the larger the cell, the more current it will produce. The resistance of the circuit of the cell will affect the current and voltage. The amount of available light affects current production. The temperature of the cell affects its voltage.

 

            Regardless of size, a typical silicon PV cell produces about 0.5 – 0.6 volt DC under open-circuit, no-load conditions. The current (and power) output of a PV cell depends on its efficiency and size (surface area), and is proportional to the intensity of sunlight striking the surface of the cell. For example, under peak sunlight conditions a typical commercial PV cell with a surface area of 160 cm^2 (~25 in^2) will produce about 2 watts peak power. If the sunlight intensity were 40 percent of peak, this cell would produce about 0.8 watts.

 

TYPES OF PV CELLS

The four general types of photovoltaic cells are:

• Single-crystal silicon.
• Polycrystalline silicon (also known as multicrystalline silicon).
• Ribbon silicon.
• Amorphous silicon (abbreviated as "aSi," also known as thin film silicon).

 

Buck-boost converter

            Buck-boost converter  circuit combines element of both buck converter and boost converter.

Working: Is to receive an input DC voltage and output a different level of DC voltage,either lowering or boosting the voltage as required by the application.

CHAPTER-7

APPLICATIONS

 

            This project can be used in Dal mill industries for long term storage at lower moisture content;

 

            This project can be used in Warehouse for a long time storage at lower moisture content;

CHAPTER-8

CONCLUSION

 

            The proposed project demonstrates how the grains after harvesting can be dried easily without any hassle and time delay. The model gave a fairly good idea of how the system can be implemented on a larger scale keeping the same idea and prospectus in mind. In addition to the time saving aspect of the farmers, it also shows how the technologically advanced controlling action, where each aspect of the grain is measured and controlled to give accurate and effective results. The proposed system is portable and handy to use and does not require any expertise on the operation as everything works automatically. The system is most suited for small and medium scale farmers who don’t have the accessibility to use technologically advanced expensive dryers. The work of the farmer is eliminated as he does not have to spread the grains across huge landfills to dry them under the sun. The drying process can be completed within a few hours in this system.

 

            Keeping the present temperature of Bangalore in mind, the output of the solar panel is good and it could achieve up to 10V, by using boost converter at the output has reached the voltage up to 30V DC with 1 amp current.

 

            The initial cost and the running cost of the proposed system is very less as all the components used are very cost effective and are readily available. The developed system can be used to dry grains such as wheat, paddy, lentils, ragi, millets, corn and coffee.

 

 

REFERENCES

 

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[2]     Chandra, D.G. and Malaya, D.B., 2011, April. Role of e-agriculture in rural development in Indian context. In 2011 International Conference on Emerging Trends in Networks and Computer Communications (ETNCC) (pp.320-323). IEEE. Parkes, D.H., Shivers Inc, 1986. Grain dryer system. U.S. Patent 4,599,809.

[3]     Tilman, D., Cassman, K.G., Matson, P.A., Naylor, R. and Polasky, S., 2002.Agricultural sustainability and intensive production practices. Nature, 418(6898), p.671.

[4]     Snaper, A.A., 2003. Method and apparatus for drying harvested crops prior to storage. U.S. Patent 6,536,133.

[5]     Suleiman, R.A., Rosentrater, K.A. and Bern, C.J., 2013. Effects of deterioration parameters on storage of maize: a review. Journal of Natural Sciences Research, 3(9), p.147.

[6]     Ahmad, I., Akhtar, M.J., Zahir, Z.A. and Jamil, A., 2012. Effect of cadmium on seed germination and seedling growth of four wheat (Triticum aestivum L.) cultivars. Pak. J. Bot, 44(5), pp.1569-1574

[7]     Datta, D., 1981. Principles and practices of rice production. Int. Rice Res. Inst.

[8]     Kiaya V 2014,Post harvest losses and strategies to reduce them.Technical paper on Post harvest losses.Action contre La Faim(ACF)

[9]     Sistler F,1987.Robotics and intelligent machines in agriculture IEEE Journal on Robotics and Automation, 3(1),pp.3-6

[10]   Sur, H.S., Prihar, S.S. and Jalota, S.K., 1980. Effect of rice-wheat and maize-wheat rotations on water transmission and wheat root development in a sandy loam of the Punjab, India. Soil and Tillage Research, 1, pp.361-371.