Communication converters are mainly used in industrial control automation systems supporting RS485 communication bus structure, including card, access control system, consumer system, attendance system, monitoring, building intercom, parking lot system, self-service banking system, bus charging system, Highway toll station system, etc. However, we will inevitably encounter various problems in the process of using the 485 converter. Next, the editor of Hangzhou Feichang Technology will introduce some common problems of the RS485 converter in detail. Interested friends Let’s take a look together!
Question 1. What is an RS485 converter?
Communication converter, also known as 485/232 converter, referred to as 485 converter, is a device that converts 485 bus communication into RS232 and connects to a computer serial port for communication. 485 converter converts single-ended RS-232 signals to balanced differential RS-485 or RS-422 signals. RS-485, RS-422 automatic identification function, easier to use.
Question 2. What is the purpose of the RS485 converter?
The converter effectively solves the following shortcomings of RS232 serial communication:
- The RS232 communication distance is theoretically more than 20 meters, and it is recommended not to exceed 13 meters in practical applications.
- RS232 communication can only carry out one-to-one point-to-point communication, that is, a serial port can only be connected to one RS232 device.
After using the RS485 converter, it can be achieved:
The theoretical distance from the computer to the last RS485 device is 1200 meters (hand in hand), and the actual recommendation is within 800 meters.
The computer can communicate with any device on the 485 bus through the 485 converter, that is, it can carry out network control of multiple devices. According to the selection and design of the chips of RS485 converters and RS485 devices (for example: access control controllers supporting RS485 communication), in theory, one bus can connect 32, 64, 128, and 256 485 devices. The actual recommendation is the theoretical value. One-third of the units are the most stable.
Communication converters are mainly used in industrial control automation systems that support RS485 communication bus structure. Including access control, food sales, monitoring, building intercom parking system, attendance and other systems.
Summary of common problems of RS485 converter
Question 3. How to choose a 485 converter?
First of all, it is recommended that you use genuine 485 converters. The price difference between genuine and non-brand converters is not much, only a few dozen dollars. In order to save costs, non-brand converters will use low-end chips or even refurbished chips.
Then, it is recommended that you choose an active converter (that is, a converter equipped with an auxiliary power supply). The difference between an active converter and a passive converter: the active converter is equipped with a Huo Niu power supply, the passive converter is not, and the active converter is not. Converters are generally about the same size as a cigarette case, while passive converters are generally slightly larger than lighters.
Disadvantages of passive converters: For cost reasons, passive converters can realize the conversion function of RS232 and RS485, but there is almost no anti-interference design. After use, sometimes the communication is normal, and sometimes the communication is abnormal. It is very unstable to use in large occasions. Passive converters have almost no protection design, let alone lightning protection. They lack strong self-protection ability against surge and static electricity. Passive converters also use the cheapest chips, so that more than a few connected devices can be easily damaged. It is unstable, and the transmission distance is also very short.
Question 4. Do I need to choose an optoelectronic isolated 485 converter?
Optical isolation is stronger than ordinary converters in terms of anti-interference and other aspects, but I personally think that its lightning protection feature seems to be the principle of self-destructive lightning protection. It protects important equipment at the back end by destroying its front end. This principle is still It will increase the maintenance workload of engineers. Therefore, when purchasing a photoelectrically isolated converter, carefully inquire about its lightning protection capability.
Question 5. What is the load capacity of the RS485 converter?
Load capacity refers to how many devices can be carried on a bus, and how far the farthest device can be connected. The load capacity is not only related to the design load capacity of the converter, but also related to the design load capacity of the 485 device. Both must be high. One of the indicators is high and useless. Some unscrupulous converter manufacturers of unscrupulous brands will falsely increase their load capacity. This requires understanding of the professional knowledge of the chip and use of the test to know, and there is a big gap between the nominal value and the actual stable application value.