Gearbox temperature online monitoring system based on wireless technology-EEWORLD

Collect

Gearbox is a very common component in mechanical equipment. How to ensure its normal operation is of great significance to the safe and reliable operation of the entire system. Due to the friction between gears, the temperature of the lubricating oil will rise. Under normal circumstances, the lubricating oil temperature of the gearbox should be limited within the allowable range. However, under abnormal working conditions, such as poor circulation, the gearbox temperature will quickly exceed the limit value. Therefore, online monitoring of the gearbox temperature can effectively warn the working status of the system and avoid the occurrence of production safety accidents.

Temperature monitoring is a mature technology at present. Most of the temperature monitoring systems widely used in industry still use wired methods to transmit signals. However, for occasions with harsh working environments, complex power supply wiring and difficult maintenance in the future, the wired method has considerable limitations. Using wireless methods to transmit data can effectively avoid these problems. Compared with wireless methods such as RF, WLAN, and Bluetooth, infrared wireless transmission is more suitable for gearbox systems in the steel production process due to its high safety, small size, low cost, and wide application. Since the

acquisition end is close to the object to be measured, wiring and maintenance are difficult, the problem of power supply and signal transmission effectiveness must be solved in system design. The limitation of wiring makes the acquisition end only adopt battery power supply mode, and online monitoring needs to work 24 hours a day, so the power consumption of the acquisition end must be very low, and the selection of devices must meet the requirements of low voltage support and low power consumption. The industrial field environment is complex and the interference is large, so the original signal must be encoded and decoded to ensure the effectiveness of signal transmission.

The acquisition and transmission end hardware design

The acquisition and transmission system is mainly composed of AT89C2051 microcontroller, DS18B20 digital temperature sensor, MC145026 encoder, TLC555 time base integrated circuit, PH303 infrared transmitting tube, etc. The system structure diagram is shown in Figure 1.

Figure 1: Structure diagram of the acquisition transmitter

The digital temperature sensor outputs the temperature signal in the form of 12-bit digital quantity, while the encoder can only complete the transmission of 4-bit binary data information at a time. When the single-chip microcomputer receives the 12-bit temperature signal, it first splits it into high, medium and low 4 bits, and then matches each bit with the corresponding address signal before sending it to the encoder. This method of address transmission can effectively avoid the problem of confusion in the transmission of different bits of information.

The effective action distance is an important parameter to measure the performance index of the acquisition transmitter. When infrared rays are emitted, the emission distance is proportional to the emission power. When the infrared emission tube works in the pulse state, the effective transmission distance of the pulsating light is proportional to the peak current of the pulse, so increasing the peak current can increase the emission distance of the infrared light. Without increasing the system power consumption, by reducing the duty cycle of the generated carrier pulse, the peak current can be effectively increased and the action distance of the infrared emission can be increased. The main function of

the monitoring receiving end hardware design

receiving end is to receive infrared signals and decode and process them subsequently. The monitoring receiving system is mainly composed of AT89C51 microcontroller, HS0038A2 infrared receiving head, MC145027 decoder, MC14511 digital driver, MAX232 serial communication chip, etc. The system structure diagram is shown in Figure 2.

Figure 2 Monitoring receiving end structure diagram

The receiving and decoding of infrared signals is carried out in a query mode. The single-chip microcomputer first sends the pre-agreed corresponding address signal to the decoder. The decoder can proofread, decode and correct the received serial data, and then output it from the parallel data port. If the address information contained in the received serial data does not match the local address information, it is regarded as invalid data. After the address check is correct, the decoder starts to decode the data. After completion, the valid output terminal of the received data outputs a high level, indicating that the decoding is valid. When the single-chip microcomputer queries the decoding valid flag, the next set of address signals is sent to the decoder.

In the decoding process, an integral link is used, that is, the decoder does not directly decode the received pulse signal, but decodes after integrating the input signal. Since the integral circuit can filter out instantaneous sharp pulse interference, the coded signal received by the decoder can still be correctly decoded even if it is interfered by a certain program, which is particularly important for industrial sites with complex environments. The

system display part adopts two display modes. One way is to communicate with the upper PC by serial data transmission, and use the rich graphical interface of the PC to display the temperature of the current device under test; the other way is to display the temperature through the digital tube of the system monitoring receiving end. This method can meet the requirements of on-site and remote temperature monitoring at the same time.

Software Design

The software of the temperature monitoring system consists of three parts. The temperature acquisition and transmission program runs in the FLASH of the AT89C2051 chip; the receiving display and serial port transmission program runs in the FLASH of the AT89C51 chip; the graphical interface and serial receiving program runs on the remote PC. The

temperature acquisition and transmission program is written in C51 language and mainly completes the following functions: (1) Reading the temperature value of DS18B20. Since DS18B20 is a one-line digital temperature sensor with high requirements for timing and electrical characteristic parameters, the acquisition program must strictly operate in accordance with the timing requirements of DS18B20. (2) Matching of encoder address and data signal. Since the digital temperature sensor outputs the temperature signal in a 12-bit serial manner, and the encoder can only transmit a maximum of 4 bits of signal each time, in order to ensure the correctness and integrity of the temperature signal, the address encoding method is adopted, that is, each time the high, medium and low 4-bit signals in the temperature signal are matched with different addresses and sent to the encoder. After the corresponding address is assigned to the decoder at the receiving end, the decoder can only receive the signal with the matching address, thereby ensuring the correctness and integrity of the temperature signal. (3) Processing of other events. Including the alarm of insufficient battery power at the acquisition end and the temperature of the measured device exceeding the standard. When the above events occur, the microcontroller will send an alarm agreement code different from the normal temperature signal, and the receiving end will make corresponding alarm processing after receiving the code. [page]

Figure 3 Collection sending end program flow

The monitoring receiving end program is also written in C51 language. Its main task is to restore the output signal of the decoder to the temperature value and display it on the on-board digital tube, and transmit it to the remote PC through the RS-232C serial bus. In addition, it can also process the received alarm agreement code to trigger various alarm states. The purpose of setting the alarm part on the receiving board is to reduce the power consumption of the sending board, thereby extending the battery replacement cycle of the transmitting end.

Figure 4 Monitoring receiving end program flow

The graphical user interface program on the PC is written in the C++ Builder development environment, and the communication is realized by the asynchronous method of port interruption. Whenever the port detects the arrival of new characters, the characters are read from the port through the interrupt function and the Tchart class and its subclasses of C++ Builder are used to display the temperature chart data in real time for the staff to view and monitor.

Conclusion

The environment around the gearbox of a certain factory is harsh, which brings great difficulties to the construction and wiring. Therefore, the ideas and structures described above are adopted in the design scheme. This system uses infrared wireless data transmission to effectively solve the problem of difficult temperature data transmission; it minimizes the power consumption of the acquisition and transmission parts, so that the battery-powered system can meet the requirements of effective operation time; the application of the matching encoding/decoding chip ensures the effectiveness and integrity of the system data transmission. The whole system can work stably in a system with harsh environment, with simple implementation, low price and good reliability, and provides a new monitoring method for online temperature monitoring in complex environments.

References:
1. Xiao Jinghe et al. Infrared, Pyroelectric and Ultrasonic Remote Control Circuits, People's Posts and Telecommunications Press, 2003.
2. Dave Hyder, Infrared Sensing and Data Transmission Fundamentals. On Semiconductor Application Note AN1016/D, 2002. (end)

Reference address：Gearbox temperature online monitoring system based on wireless technology

Previous article：Design of a simple digital oscilloscope based on single chip microcomputer
Next article：Design of solar semiconductor air conditioning control device

Popular Resources
Popular amplifiers