485 Isolation Circuit Scheme

Posted by uartmodule

1. What is 485 isolation circuit?
RS-485 is a commonly used data communication protocol, widely used in industrial control systems, building automation, security systems and other fields. In some applications, the RS-485 interface needs to be isolated in order to prevent electrical noise interference or electrical shock.

Sample image (for reference only)

2. What methods can realize 485 isolation circuit?

If you want to achieve isolation on the 485 circuit, you need to use isolation devices, such as optocoupler isolators, magnetic isolators, etc. The specific implementation steps are as follows:

Using an isolator: First, you need to choose a suitable isolator. Common RS-485 isolators include ADI's ADM2483, TI's ISO3082, etc. These isolators typically integrate an RS-485 transceiver and an isolated power supply that can provide isolation voltages up to 2500V.

Power supply design: The isolator needs two independent power supplies, one for the circuit before isolation (such as MCU), and one for the circuit after isolation (such as RS-485 bus). Isolated power can be achieved using an isolated DC-DC converter.

Interface design: RS-485 interface usually requires a 120-ohm terminal resistor to suppress signal reflection. In addition, TVS diodes and ferrite beads can be added for electrostatic discharge protection and high frequency noise filtering

Wiring design: In order to reduce electromagnetic interference, the A and B lines of RS-485 should run together as much as possible, and keep away from high-speed or high-current signal lines as much as possible.

Software design: In the software, it is necessary to correctly set the working mode of the RS-485 transceiver (such as half-duplex or full-duplex), and set the data rate, data bits, stop bits and parity bits as required.

What we need to pay attention to is that the specific design may need to be adjusted according to actual application requirements and environmental conditions. At the same time, it is also necessary to pay attention to the selection and quality of the isolation device to ensure the stability and reliability of the isolation circuit.

What are the benefits of the 3.485 isolation circuit scheme?

Improve the reliability and stability of communication: The isolation circuit can prevent electrical noise and electrical shock from interfering with the system, thereby improving the reliability and stability of the system.

Protect the safety of the equipment: the isolation circuit can prevent the damage to the equipment caused by the high voltage shock, so as to protect the safety of the equipment.

Improve signal quality: The isolation circuit can reduce the interference during signal transmission, thereby improving the quality of the signal.

Extended system distance: RS-485 interface can support long-distance data transmission, and the isolation circuit can further extend this distance.

Improving system flexibility: The isolation circuit can make the system more flexible in design and layout, and devices can be placed in different locations according to needs.

 Good compatibility: RS-485 isolation circuit scheme can be compatible with various equipment and systems, which is convenient for system integration and expansion.

Preventing ground loops: The isolation circuit can prevent the generation of ground loops, thereby avoiding damage to equipment due to excessive current caused by ground loops.

From our safety point of view, the RS-485 isolation circuit solution can improve the reliability, safety and flexibility of the system, and is an ideal choice for industrial control systems, building automation, security systems and other fields.