Question 1: What is an RS485 converter?

An RS485 converter, also known as a 485/232 converter, is a device that allows communication between a computer's RS232 serial port and devices using the RS485 bus protocol. It acts as a bridge, enabling data exchange over longer distances and in more complex network setups than what RS232 alone can support.

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

The main purpose of an RS485 converter is to overcome the limitations of traditional RS232 communication. For instance:

• RS232 has a limited range—typically no more than 13 meters in real-world applications.
• It only supports point-to-point communication, meaning each serial port can only connect to one device at a time.

With an RS485 converter, you can extend the communication distance up to 1200 meters theoretically, with a recommended maximum of 800 meters for stable performance. It also enables multi-drop communication, allowing a single computer to communicate with multiple devices on the same RS485 bus. Depending on the chip design, a single bus can support up to 256 devices, though it's safer to use about one-third of that number for optimal stability.

These converters are widely used in industrial automation systems such as access control, surveillance, building intercoms, parking systems, and attendance management.

Question 3: How to choose an RS485 converter?

When selecting an RS485 converter, it’s best to go for a genuine product from a trusted brand. While the price difference between original and counterfeit models may be small (usually just a few dollars), the quality and reliability are significantly different. Some cheaper alternatives may use low-quality or even recycled chips, which can lead to unstable performance.

Another important consideration is whether to choose an active or passive converter. Active converters come with an external power supply and are generally more reliable, especially in environments with electrical noise. Passive converters, on the other hand, rely solely on the power from the serial port and often lack sufficient protection against interference and surges. They are typically smaller but less robust, making them unsuitable for large-scale or mission-critical applications.

Question 4: Is it necessary to use an opto-isolated RS485 converter?

Opto-isolated converters offer better noise immunity compared to standard ones. However, their lightning protection mechanism is usually based on a "self-destructive" principle, where the front-end components are sacrificed to protect the downstream equipment. This can increase maintenance efforts, so it's important to check the actual lightning protection rating before purchasing.

Question 5: What is the load capacity of an RS485 converter?

Load capacity refers to how many devices can be connected to a single RS485 bus and how far the farthest device can be located. This depends not only on the converter’s design but also on the capabilities of the connected RS485 devices. If either component is low quality, the system will not perform well. Some manufacturers may exaggerate their load capacities, so it's essential to test the converter under real conditions. There is often a gap between the advertised specifications and the actual performance in the field.