Summary of common problems with RS485 converter

Question 1. What is an RS485 converter?

The communication converter is also called 485/232 converter, referred to as 485 converter. It is a device that converts 485 bus communication into RS232 computer serial port for communication.

Question 2: What is the purpose of the RS485 converter?

The converter effectively solves the following shortcomings of RS232 serial communication:

1, RS232 communication distance, theoretically more than 20 meters, the actual application is recommended not to exceed 13 meters.

2. RS232 communication can only perform one-to-one point-to-point communication, that is, one serial port can only connect one RS232 device.

After using the RS485 converter, you can achieve:

The theoretical distance from the computer to the last RS485 device is 1200 meters (hand in hand), the actual recommendation is within 800 meters.

The computer can communicate with any device on the 485 bus through the 485 converter, which means that multiple devices can be networked. According to the selection and design of the chip of RS485 converter and RS485 device (for example, the access controller supporting RS485 communication), theoretically, one bus can connect 32 sets of 64 sets of 128 sets of 256 sets of 485 devices. The actual recommendation is theoretical value. One third of the numbers are the most stable.

Communication converters are mainly used in industrial control automation systems that support the RS485 communication bus structure. These include access control, food sales, monitoring, building intercom parking system, attendance and other systems.

Question 3, how to choose 485 converter?

First of all, it is recommended that you choose the authentic 485 converter. The price difference between the genuine and miscellaneous converters is not large, only a few tens of dollars. The converters of the brand will use low-end chips or even refurbished chips in order to save costs.

Then, it is recommended that you choose the active converter (that is, the converter with the auxiliary power supply) the difference between the active converter and the passive converter: the active converter is equipped with the AC adapter power supply, the passive converter is not, the active Converters are generally similar in size to cigarette packs, while passive converters are generally slightly larger than lighters.

Disadvantages of passive converters: Due to cost considerations, passive converters can realize RS232 and RS485 conversion functions, but there is almost no anti-interference design. After use, sometimes communication is normal, sometimes communication is abnormal, and environmental interference is compared. The use of large occasions is very unstable. Passive converters have almost no protection design, let alone lightning protection. They lack strong self-protection ability for surge static electricity, and passive converters use the cheapest chips, making more than a few connected devices. Unstable, the transmission distance is also very short.

Question 4: Is it necessary to use an opto-isolated 485 converter?

Photoelectric isolation is stronger than ordinary converters in terms of anti-interference, but I personally think that his lightning protection characteristics seem to be the principle of self-destructive lightning protection. By destroying the front end to protect the important equipment at the back end, this principle is still Will increase the maintenance workload of the engineer. Therefore, when purchasing an opto-isolated converter, ask him about his lightning protection capability.

Question 5, 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 which is high and useless. Some unscrupulous converter manufacturers of miscellaneous brands will falsely mark their own load capacity. This requires knowledge of the chip's expertise and use of the test to know, and there is a big gap between the nominal value and the actual stable application value.