Vegetable Greenhouses Intelligent Temperature Control System

This study is designed for microcontroller-based system to monitor the data greenhouses, especially to ensure that a constant temperature inside the greenhouse to ensure the crop. By DS18B20 temperature measurement and display and LCD were working with the information obtained to adjust the device so that the temperature control and thus achieve the optimum production temperature and increase production.


INTRODUCTION
In China's northern region, due to its high latitude, the four seasons and a relatively large temperature difference between day and night and the long and cold winter, which suitable crops (Long et al., 2013).Therefore, the development of a comprehensive solution can detect temperature information systems, especially to be able to multi-point temperature measurement system is very important.Relying on the experience and the human cost is too high, while it does not have the science, susceptible to interference and influence production capacity, is not conducive to the controller to make the right decision.
The main topic of vegetable greenhouses to achieve intelligent temperature control: temperature display, temperature setting, alarms, data communications, temperature control, etc. Lower machine functions (MCU section): • Temperature warning: When the environment temperature exceeds a preset range, the use of sound and light devices alarm The aim of this study is that the temperature in vegetable greenhouse gets on real-time monitoring and control system, temperature control system witch designed achieves the basic temperature control (Yan et al., 2013).

MATERIALS AND METHODS
System hardware components: This design is an automatic detection and automatic temperature control system (Nakamoto et al., 1997), lower computer system hardware mainly contains: AT89C51 microcontroller, sensors, LCD displays, motors and alarm buzzer LED devices.Composition is shown in Fig. 1.
As shown in Fig. 2, AT89C51 is the central system.First, it is detected by the temperature, the results of the previous step are on the motor to automate the control and display the results.If the detected temperature is higher than the set value, an alarm to start the motor, the corresponding air-conditioning system is turned on.
The working principle of DS1820: As shown in Fig. 3, DS1820 pin I/O-bit data input/output (single wire bus) is an open-drain output.If connected to an external pull-up resistor, this is often the case is high.VDD 5V power supply terminals can be used for an optional external power supply, often require ground when not in use.GND is the ground pin and NC is empty feet.

Alarm circuit:
Circuit alarm siren alarm is the main component, its main advantage is that by constantly issuing pronunciation components siren judge line on or off.And buzzer alarm circuit produces about 3 Hz shock sound received between 3V and 5V DC power supply will be able to achieve.The circuit is shown in Fig. 4.

RESULTS AND DISCUSSION
Overall summarize, the general software can be divided into four categories: The first type is a measure of software, mainly for temperature monitoring.Second display portion for displaying the temperature detected at the time.Third, the regulation section for controlling the rotational speed of the motor.Fourth, when the temperature is higher than the set temperature threshold, the buzzer will automatically send an alarm signal.Figure 5  Instrument obtained from a single bus power and when high signal lines energy stored on the internal capacitance, at the time of the low signal, the system will disconnect the power until the power supply is not only a low level.Moreover, external 5V power provides power to achieve DS18B20.As shown in Fig. 7.
Reading the temperature subroutine can read 9 bytes in RAM.When nine of the bytes are read, CRC will begin testing.When an error occurs after the check, it will not be rewritten temperature data.Motor control: If the temperature is below 28°C, at the time of the P1.7 angle output signal is one, the motor does not rotate.Temperature between 28-40°C, the motor starts to work, the duty cycle is 0.5.Temperature is between 25-30°C, the duty cycle is 0.75.Temperature is between 30-35°C, the duty cycle reaches 0.9375.The higher temperature, the easier to achieve balance.

CONCLUSION
This design is the application of microcontrollers and digital temperature sensor for design.The system can achieve the indoor temperature and humidity automatic adjustment and measurement can reduce the labor intensity of staff.In the northern cold season long, the biggest difference between day and night and seasonal temperatures is also great, is not conducive to the growth of crops, In this form, the development of high-precision, real-time high, the system can accurately to handle multi-site temperature information is essential.In contrast, currently the only rely on past experience and manpower to monitoring and control system could not be more scientific.In this environment, highprecision, high-availability, low cost, temperature Data communication: The use of serial or wireless communication (GPRS) and the temperature information in real time to spread the host computer (PC) and stored (Yan et al., 2014a) • Temperature control: According to the temperature setting, the thermostat device turned on or off in time • Temperature display: The use of the LCD display shows vegetable greenhouse temperature.PC functions: o To accept and store temperature data o Temperature parameters seto With temperature display, query and analysis (Line chart)(Yan et al., 2014b)

Fig. 4 :
Fig. 4: Buzzer circuit is a software design flow.Read the temperature design: Figure 6 are AT89C51 and DS18B20.