Engineering Student Projects Training Embedded Six Weeks

Green Bee

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The objective of this project is to design a simple, easy to install, microcontroller-based
circuit to monitor and record the values of temperature, humidity, soil moisture and sunlight of
the natural environment that are continuously modified and controlled in order optimize them to
achieve maximum plant growth and yield. The controller used is a low power, cost efficient chip
manufactured by ATMEL having 8K bytes of on-chip flash memory. It communicates with the
various sensor modules in real-time in order to control the light, aeration and drainage process
efficiently inside a greenhouse by actuating a cooler, fogger, dripper and lights respectively
according to the necessary condition of the crops. An integrated Liquid crystal display (LCD) is
also used for real time display of data acquired from the various sensors and the status of the
various devices. Also, the use of easily available components reduces the manufacturing and
maintenance costs. The design is quite flexible as the software can be changed any time. It can
thus be tailor-made to the specific requirements of the user.

This makes the proposed system to be an economical, portable and a low maintenance
solution for greenhouse applications, especially in rural areas and for small scale agriculturists.

SENSOR’S:

TEMPERATURE SENSOR

In this project we use many sensor’s . Out of these sensor’s one sensor is temperature sensor. Here in this project we use LM 35 as a temperature sensors. LM35 is very accurate and very good sensor to show the temperature in celicus. For body temperature measurement we use IC LM34 sensor. LM35 is a linear temperature sensor. To convert this output for the input of the ADC we use op-amp  current amplifier to convert the signal into 0-5volt dc.Here in this project we use  op-amp op07 ( industrial amplifier ).LM 35 is connected to the pin no 3 of the op-amp via 2.2k ohm resistor. Pin no 2 which is –ve input of the op-amp is set to the reference voltage by 1k variable resistor. Centre point of 1 k ohm resistor is connected to the pin no 2 via 10 k ohm resistor. Positive voltage is also applied to the one shaft of the preset via 3.3k ohm resistor. 4.7k ohm resistor is also grounded from the 1k variable resistor. Pin no 7 of the ic is connected to the positive  5 volt . Pin no 4 is connected to the common ground point. One feedback resistor is connected from output pin to the pin no 2 which is 50 k ohm resistor. So by this way we set the gain of 5 by this opamp. We set the minimum reference voltage by preset ( variable resistor) and when temperature rises then output is also increases with the gain of 5 and connected to the  IN0 input of the ADC.

Temperature Sensor – The LM35

The LM35 is an integrated circuit sensor that can be used to measure temperature with an electrical output proportional to the temperature (in oC)

The LM35 – An Integrated Circuit Temperature Sensor

  • Why Use LM35s To Measure Temperature?
    • You can measure temperature more accurately than a using a thermistor.
    • The sensor circuitry is sealed and not subject to oxidation, etc.
    • The LM35 generates a higher output voltage than thermocouples and may not require that the output voltage be amplified.
  • What Does An LM35 Look Like?
  • What Does an LM35 Do?  How does it work?
    • It has an output voltage that is proportional to the Celsius temperature.
    • The scale factor is .01V/oC
    • The LM35 does not require any external calibration or trimming and maintains an accuracy of  +/-0.4 oC at room temperature and +/- 0.8 oC over a range of 0 oC to +100 oC.
    • Another important characteristic of the LM35DZ is that it draws only 60 micro amps from its supply and possesses a low self-heating capability. The sensor self-heating causes less than 0.1 oC temperature rise in still air.

The LM35 comes in many different packages, including the following.

  • TO-92 plastic transistor-like package,
  • T0-46 metal can transistor-like package
  • 8-lead surface mount SO-8 small outline package
  • TO-202 package. (Shown in the picture above)
  • How Do You Use An LM35?  (Electrical Connections)
    • Here is a commonly used circuit.  For connections refer to the picture above.
    • In this circuit, parameter values commonly used are:
      • Vc = 4 to 30v
      • 5v or 12 v are typical values used.
      • Ra = Vc /10-6
      • Actually, it can range from 80 KW to 600 KW , but most just use 80 KW.
    • Here is a photo of the LM 35 wired on a circuit board.
      • The white wire in the photo goes to the power supply.
      • Both the resistor and the black wire go to ground.
      • The output voltage is measured from the middle pin to ground.l

Here we use lm 35 is connected to the op-amp circuit to amplify the current Output of the LM35 is further connected to the pin no 26 of the ADC. Here we use 0809 Adc to convert analogue signal into digital signal. This signal is further connected to the microcontroller.

 SOIL MOISTURE SENSOR.

In the soil moisture sensor we check conductivity of the soil . for this purpose we insert two probes in the field. If the field is wet then conductivity is more and resistance is less. If the field is dry then conductivity is less and  resistance is high. To measure the conductivity we use one NPN transistor  circuit. Emitter of the NPN transistor is connected to the input of adc and collector of the transistor is connected to the positive supply 5volt. Base is biased through positive voltage through 100 ohm resistor in series with the conductivity probe. Emitter voltage is also set by the one variable resistor 10 k. One point of the 10 k ohm resistor is connected to the positive point and  third point of the 10 k ohm resistor is grounded. Centre point of the 10 k ohm resistor is connected to the emitter of the transistor and go though the  input of ADC IN2. As the base voltage is change according the  resistance of the field. ADc input is also change .

LIGHT SENSOR:

In the light sensor we use one LDR. LDR is a light dependent resistor. Resistance of the ldr is depend on the intensisty of the light. As the light on the ldr is change , resistance of ldr is also change. Resistance of the ldr is varies from 1k ohm to 500 k ohm. In full llight resistance of the ldr is very low   below then 1 k ohm and in no light resistance of the ldr is become very high above then 500k ohm.

In this project we use ldr with only one 10k ohm variable resistor. This 10 k ohm resistor is connected to the positive voltage 5volt.

CIRCUIT WORKING:

OUR complete  project is to be divided into  6 sections.

Power supply.

Sensor signal conditioning

Analogue to digital converter.

Microcontroller interface.

LCD  connectivity.

Output interface.

POWER SUPPLY

5 VOLT REGULATED POWER SUPPLY CIRCUIT.

In this project firstly we use one step down transformer. Step down transformer step down the voltage from 220 volt Ac to  12 volt Ac. This Ac voltage is further converted into DC with the help of rectifier circuit. In rectifier circuit we use four diode. All the diodes  are arranges as a bridge rectifier circuit. Output of this rectifier is pulsating Dc. To convert this pulsating DC into smooth dc we use one capacitor as a filter components. Capacitor converts the pulsating Dc into smooth DC with the help of its charging and discharging effect.

Output of the rectifier is now regulated with the help of  IC regulator circuit. In this project we use positive voltage regulator circuit. Here we use three pin regulator. Output of this regulator is regulated voltage. If we use 7805 regulator then its means its is 5 volt regulator and if we use 7808 regulator then its means that it is 8 volt regulator circuit. In this project we use 5 volt dc regulated power supply for the complete circuit.

Appropriate environmental conditions are necessary for optimum plant growth, improved
crop yields, and efficient use of water and other resources. Automating the data acquisition
process of the soil conditions and various climatic parameters that govern plant growth allows
information to be collected at high frequency with less labor requirements. The existing systems
employ PC or SMS-based systems for keeping the user continuously informed of the conditions
inside the greenhouse; but are unaffordable, bulky, difficult to maintain and less accepted by the
technologically unskilled workers.

ADVANTAGES

Low cost

Reliable

Portable

Flexible  due to microcntroller

Easy to use- system is very easy to understand

It wil also help in irrigation department for farmers to control temperature

Features-

Microcontroller 8051 or PIC controller

LCD display

Sensors

·        Moisture

·        LDR

·        Temperature

Hardware required-

8051 programmer universal kit

CRO 20 Mhz

Digital multimeter

Software required:

Keil software- Microvision 2- we will use keil software to compile and

simulate  program file. We can write programming code in C or assembly language file

ORCAD for PCB design 10.5 – we will design layout in ORCAD software.

Proteus for simulation 7.4 version- we will use proteus softw

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