Industrial sites often need to isolate RS-232 and RS-485 at the same time, usually using two isolated DC-DCs with separate signal isolation circuits, but the isolation performance is different and it takes up a large board area. This article will introduce you to a fully isolated solution that is stable, reliable and easy to apply.
1. Brief description of the interface circuit of the communication management machine
The communication management machine can collect data from multiple subsystems in the power system, and complete the data interaction in the power system through centralized processing and receipt. Externally, it is usually necessary to integrate multiple RS-232, RS-485, CAN, Ethernet interfaces, etc.
Figure 1 Application topology of communication management machine
The communication management machine has high requirements for the interface resources of the embedded main control CPU, and it is often necessary to expand the communication interface in various ways; at the same time, the working environment of the power communication equipment is more complicated, and there is a rigid demand for isolation and anti-interference performance. However, according to the conventional design plan, the interface isolation circuit designed with discrete isolation DC-DC, signal isolation, transceiver, protection circuit, etc. occupies a large PCB area, and there are many types of materials purchased, and it is not convenient to test the performance of the communication interface separately. .
Figure 2 Common communication management machine
The following shows the extended resource IO board required by common communication management machines. The communication interfaces include CAN, RS-485 and RS-232. Conventional module solutions can use the CTM1051KT, RSM485ECHT and RSM232 isolation modules of Zhiyuan Electronics. Although the volume is greatly improved compared with the discrete solution, it is not the best solution. The following will introduce you to solutions with higher product integration and more convenient application.
Figure 3 Common communication management machine
2. Combined application of MPM features and communication management machine
ZLG Zhiyuan Electronics’ MPM series modules creatively combine the commonly used RS-232 and RS-485, combined with the application of the communication management machine, and the additional advantages they bring are mainly as follows:
Some details of the electrical parameters of MPM are as follows:
Figure 4 MPM module selection table
3. Application of MPM connected to RS-232 to RS-485
Because MPM's RS-485 supports automatic flow control, it means that only TXD and RXD are needed to complete RS-485 communication. Therefore, cross-connect the RS-232 and RS-485 UART ports of MPM products to support the conversion of RS-232 to RS-485. At the same time, there is complete electrical isolation between RS-232 and RS-485. For debugging serial ports, It is very convenient to isolate bus interference and other applications, as shown in the figure below.
Four, summary
According to the current communication isolation requirements of industrial products, the MPM series of multi-protocol isolation modules have been specially developed. The isolated power supply, communication isolation circuit, and ESD protection circuit are integrated and packaged in one module, and the circuit design is reduced to a single piece, requiring only simple electrical connections. , It can realize RS-485/232 communication isolation, and the isolation voltage is as high as 3500VDC, which can meet the needs of most applications.
With the rapid development of science and technology today, due to the many design requirements of industrial products, it is difficult to achieve the same exquisiteness as consumer products such as mobile phones, but the miniaturization of industrial products is inevitable. The use of a module may not be able to completely get rid of the image of "silly, big and clumsy" for industrial products, but ZLG Zhiyuan Electronics has been working hard on the road of miniaturization and modularization of industrial products, an explorer.
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