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In food storage, temperature and humidity are the most critical factors in ensuring food storage security. The use of temperature and humidity recorder allows us to monitor the grain warehouse more quickly and accurately. The temperature and humidity recorder measures the indoor temperature and humidity accuracy is high, the error is small, the operation is simple, the stored data up to 10,000, for the food Storage security provides scientific assurance. Today we introduce the structure and principle of a new temperature and humidity control system and its application in grain storage.
First, the composition of temperature and humidity control system
1. The code tube display is used to display the temperature and humidity of the granary and also used for alarm display. With four digits to display temperature and humidity, a display bin number, a display position, temperature and humidity can be differentiated by the second decimal place. Therefore, six digits are shared.
The display is connected to the microcontroller 8031 ​​through a programmable chip 8 . The B port is used as the segment code output of the monitor, and the C port is used as the bit code output of the monitor.
2. There is no program memory inside the 8031, so it is an external 2716. In addition, although there are 128 data storage units within the 8031, there are 256 data storage units within the 8155, but the system needs to collect, calculate, and process a large amount of data, so an extension of 6116.
3/ sound and light alarm granary in the four seasons, the temperature and humidity are very different. However, the temperature and humidity of the same position in each season are generally the same in each season. Therefore, the temperature and humidity of the same position in each granary are lined up. If the deviation of a certain value from the median exceeds a certain value, in addition to the digital display, the monitoring room also needs a light alarm. . Absolute value of temperature and humidity exceeds a certain limit but also alarm.
Second, system software design
The system software consists of a main program, data acquisition subroutines, display subroutines, timer interrupt service routines, and delay subroutines. In addition, as mentioned above, the system requires a large amount of data to be calculated and processed. Therefore, a series of MCS one-floating-point floating-point calculation subroutines are also compiled and referenced for data processing subroutine calls. In the program design, a combination of modular and structured programming techniques is used to improve efficiency, save space, and facilitate debugging and use of the program. Due to limited space system software block diagram and the subroutine block diagram slightly.
Third, improve the reliability of the system
Although the system is operating in a non-industrial environment, the operating practice shows that interference is everywhere. To make the system run reliably, the necessary hard and software measures are not taken. The main anti-interference measures adopted by this system are as follows:
1, hardware measures
(l) Power supply and grounding In the power supply, lead wires are added to the capacitance filter, and the system is separated from the strong battery. The internal components of the system follow the principle of “single point groundingâ€.
(2) All shielded signal cables use shielded cables.
(3) Opto-isolation The photoelectric isolator is provided at the final stage of the output interface to separate the digital circuit from the strong circuit.
2, software measures
(1) The digital filter adopts the median filtering method of five times sampling to take the median value.
(2) To prevent the program from "runaway" by using the internal timer TO to set "wATCHINGI)OG" and monitor whether the program is running normally, that is, in the main program and each subroutine of the cyclic operation, the timer is triggered repeatedly, and Its timing value is set slightly larger than the program's maximum possible cycle time. When a disturbance causes Moo to run away, the system enters the timer interrupt service routine. The main content of the timer interrupt service routine is to automatically return the program population to normal loop.
Fourth, the conclusion
Because the system has adopted a series of hardware and software anti-jamming measures, the system operates reliably. In data acquisition and data processing, due to the high sensitivity of the sensor and software compensation measures, the temperature error is <1°C and the relative humidity error is <5%, which meets the requirements of the design specifications.
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