The development of digital technology shows the advantages that traditional technology can't match. The signal sampling, processing, control and communication of the entire power monitoring system can be realized by digital technology. The fully digital control technology can effectively reduce the size of the device and reduce the cost of the device, but at the same time greatly improve the reliability, intelligence and user experience of the device. As the module becomes more intelligent, the maintainability of the new power monitoring system has also been improved.
With the development of embedded technology, the use of embedded real-time operating system is an inevitable choice for power monitoring systems. On the one hand, the embedded real-time operating system has good portability and high reliability; on the other hand, because with the continuous improvement of the performance of the power monitoring system, only the traditional single-chip microcomputer can not adapt to the new demand. As the representative of today's embedded technology, ARM not only has all the above advantages, but also has low cost and high cost performance. The system designed in this paper uses the LM3S9B96 chip from the Luminary Cortex-M3 series ARM produced by TI.
1 Working principle
Figure 1 shows the principle block diagram of the monitoring system by taking the power monitoring of the 8-way electrical equipment as an example.
Figure 1 Block diagram of 8 power supply monitoring system
All eight devices draw power from the main power supply, and each power supply branch works in exactly the same way. After the power monitoring system is started, the main chip is in the power-on reset state, and the eight I/O pins of the GPIOF are at a low level. At this time, the electronic control switch remains in the off state, that is, the power supply branch is in the power-off state. When the main chip core and each peripheral are successfully initialized, the output of the 8 I/O pins of the GPIOF is controlled to be high by its internal embedded program. Accordingly, the power supply branches are energized and start normal operation.
The acquisition module includes a current sensor and a voltage dividing circuit. The current sensor can measure the current value flowing through the power supply branch, and the voltage dividing circuit adjusts the voltage value of the power supply branch to the range of the sampling of the main chip ADC, both of which are analog values. . After the detected value is sampled by AD, the current and voltage values ​​of each power supply branch can be calculated in the main chip and compared with the preset current and voltage thresholds. If it is within the threshold range, it indicates that the power supply branch is working normally, and outside the threshold range, it indicates that the power supply branch has abnormalities such as overcurrent, overvoltage, undervoltage, etc., and the main chip changes the output of the corresponding pin of the GPIOF. Low level to automatically power off the branch. After checking and troubleshooting, the power supply branch can be controlled by the host computer to issue power.
The upper computer communicates with the embedded lower computer through Ethernet. The upper computer can send commands to the lower computer to control the on/off of the specified power supply branch, and can also set the current and voltage threshold values ​​of each power supply branch. At regular intervals, the current, voltage value and various normal/abnormal states of each power supply branch are sent to the upper computer by the lower computer. The working status of each power supply branch can be observed through the upper computer display control software.
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