Design of Intelligent Temperature Controller for Dry-Type Transformer Based on ATmega16 Single Chip Microcomputer

The software adopts a modular structure, including 1 main module and 5 submodules (button processing submodule, digital quantum module for setting upper limit temperature and collecting boundary points, communication submodule, fault output processing submodule and display submodule). The main module completes the initialization of each submodule and calls the fault output processing submodule and display submodule. The button processing submodule, digital quantum module for setting upper limit temperature and collecting boundary points and communication module work in interrupt mode, and the main module communicates with them through a shared RAM area. Since the analog input signal of the single-chip microcomputer application system contains various noises and interferences, this program uses digital filtering technology to filter. In addition, for the linearization problem mentioned above, we divide 0~200℃ into four areas and perform linearization calculations in each area. This is much more accurate than directly calculating in the 0~200℃ area and can achieve an accuracy of 0.1℃.
The functions of each submodule are as follows:
(1) The button processing submodule applies for an interrupt to ATmega16 when a key is pressed, and modifies the pre-set flag in the interrupt subroutine. (2) Setting the upper limit temperature and collecting boundary points The digital quantum module can enter the interface for modifying the upper limit temperature by entering the password when the key is pressed for a long time. The digital quantities corresponding to 0℃, 50℃, 100℃, 150℃, and 200℃ are collected through the button, and the results are stored in the E?2PROM. This data is used as the boundary point to calculate any temperature between 0 and 200℃. (3) The communication submodule can connect the remote controlled object through the LBC184 (converting RS232 signals to RS485 signals) chip and the single-chip microcomputer for RS485 communication. (4) The fault output submodule can judge whether there is an abnormal situation on site by comparing the actual temperature with the upper limit temperature. At the same time, the flag bit is set to determine whether to perform A/D conversion and whether to display. (5) The display submodule converts the results of linear calculation from binary to BCD code and sends them to the 5-bit LED display for display.

(1) To solve the AC power interference in the temperature controller, a power filter is connected in series at the incoming end of the AC power, that is, the primary end of the power transformer. This can effectively suppress the intrusion of high-frequency interference (Figure 4).

(3) Use varistors at both ends of the temperature sensor in the analog conversion circuit and other places to absorb overvoltages of different polarities.
(4) Conduct electromagnetic interference tests at the dry-type transformer operation site, conduct probability statistical analysis on the test results, and minimize the electromagnetic interference generated by the interference source by carefully selecting components and using hardware anti-interference technology and software anti-interference technology.
The temperature controller has low power consumption, advanced technology, complete functions, simple operation, reliable performance, and can work stably for a long time in very harsh electromagnetic interference or high temperature environments. It is an ideal monitoring device for dry-type transformers.