Greenhouse warming is realized by using PLC control method

This paper introduces the PLC to realize the greenhouse temperature control method, in this way, the PLC interface circuit is simple, less peripheral components, the whole system has high reliability, guarantee the quality of the greenhouse temperature control. Of the 1

in agricultural greenhouse cultivation, temperature is an important control parameter, crops each time 24 hours a day on the temperature requirements are different, this is the crop of circadian rhythm, is also a long-term practice of crop expert experience, for example: cucumber, tomato and melon in 24 hours each time requirement for temperature as shown in table 1.

several crop temperature management table to table 1

greenhouse temperature control is described in table 1 crop requirement of living environment, now white spines cucumber plants, for example, introduces the PLC as the control core, design of greenhouse temperature control system hardware circuit and software programming and the matters needing attention.

2 hardware circuit of the control system of greenhouse warming

2. 1 white spines cucumber crop the curve of variable temperature requirements

convenient for later analysis, described in table 1 white cucumber variable temperature requirements, represented in figure 1 curve. Figure 1

white spines cucumber ( Sunny day) 24 hours production environment temperature change curve

analysis according to the figure 1 curve, the curve of a total of 4 hours, four temperature hope value ( Given value) , after 24 hours, continuous cycle, including under cloudy conditions, also requires a 17 - - - - - - - - - - - - - 21 points temperature for a given value of 14 ℃ ( As shown in dotted line) 。 The entire electrical system based on the design of hardware and software to 1.

2。 2 the greenhouse temperature measurement and A/D conversion circuit

figure 2 PLC interface, temperature measurement and A/D conversion circuit

2. 3 in the selection of PLC and temperature display circuit

PLC selection of Japan mitsubishi FX2 - 16 points, 32 mt type, input output 16 points, with functions of high speed counter, using all the counter below 20 KHZ frequency combined. ( This example X0 signal input frequency limit of 8 KHZ, X1 input signal frequency limit of 6 KHZ) The PLC is also equipped with instruction rich configuration software, fully meet the requirements of control.

choose PLC power supply + 24 v and not use ~ 220 v power supply, mainly in order to overcome the utility power cuts, UPS internal switch instantaneous losing electricity will cause confusion, PLC timing circuit adopts + 24 v power supply, and high-capacity capacitor at both ends, can avoid this problem very well. Temperature display circuit with a latch 7 shows four digital tube, via an external switch point can be viewed the greenhouse inside and outside the greenhouse temperature.

2。 4 equipment of warming and cooling

warming device adopts air heating, using electric heating and ventilation cycle to achieve the purpose of warming, if need to heat up, set the temperature is lower than the temperature outside, also can be directly use ventilation and circulation in temperature (in the form of This way can reduce the energy consumption) 。

cooling adopts two steps (1) outdoor temperature is lower than the indoor temperature is lower than the setting temperature, ventilation and circulation mode can be used. (2) the outdoor temperature is higher than the setting temperature, small greenhouse can use air conditioning, ( Big greenhouse roof water cooling method) Warming and cooling control is an important content of PLC programming should be considered. 3 PLC control program

clock is formed, in each period for a given input, the measured temperature and gives quantitative comparison ( Several of the selected parameter K program) Display program, as shown in figure 3.

figure 3 clock, data given, compare and display program

paragraphs in heating and cooling control program as shown in figure 4.

figure 4 raising temperature, temperature control program

4 working principle of the control system of greenhouse warming

as shown in figure 2, figure 3, figure 4. At 6 o 'clock in the morning on switch K, PLC electricity work. On the one hand, M8014 ( 1 minute pulse) Into C0 count, when C0 360, equivalent to 6 hours, in this time period is equal to 6 - - - - - - - - - - - - - After 12 o 'clock, when C0, M8014 into C1 counter counts, C1 is 300, equivalent to 5 hours, in this time period is equal to 12 - 17 points, when C1 is into the C2 pulse counting M8014 action, C2 240 is equivalent to 4 hours, in this time period is equivalent to 17 - 21 points.

after the C2 action M8014 into C3 count, when C3 540, equivalent to 9 hours, in this time period is equal to 21 - - - - - - - - - - - - - - - - - - - At 6 o 'clock, The second day) 。 When C3 movement, M1 pulse, for CO, C1, C2 and C3 all O, cycle count again. To complete the purpose of adopting PLC to realize the clock program, use the UPS, and capacitance C ( In figure 2) Main grid fault cases can still guarantee to guarantee the accuracy of the clock.

, on the other hand, in each period, for a given value and the temperature in greenhouse. Comparison of the given value and the greenhouse temperature according to the comparison results, decided to use warming or cooling. If conditions meet, can be directly used to smoke, air supply solutions, warming or cooling problem.

exist in each temperature change during the transition process, the steady temperature was also warmer ( Or cooling) Constantly adjusting process ( As shown in figure 1 dotted line part of the curve) And, therefore, KM1, KM2, KM3, KM4 had better choose solid state relay. ( Non-contact, no action spark) , increase the working reliability of components and equipment. 5 conclusion

PLC controller can realize the control of greenhouse warming, this design is based on the unmanned automatic operation variable temperature control system, if you want to change in the production of crop varieties, only need to change the data in figure 3 can be. Other hardware configuration and 4 basically the same, so can be convenient to control the greenhouse temperature, the purpose of better meet crop production.

Over the years, has become very popular as more and more people are trying it out.
We are an experienced supplier of and have gained good reputaion among global customers. With a wide range of in offer, we can customize according to your requirement. Send us your enquiry at Coolmay PLC.
Shenzhen Coolmay Technology Co., Ltd. 's core technology of plc manufacturers enables us to understand and utilize in a right way.
Many homeowners find that they can cut costs while keeping home cool efficiently with .