RS485 is a serial communication standard that was introduced in 1983. It is widely used in industrial applications for its reliability, robustness, and long-distance communication capabilities. RS485 is a half-duplex communication protocol, which means that data can be transmitted in both directions, but not simultaneously.
RS485 is a serial communication standard that is used to transmit data over long distances. It is a differential signaling standard, which means that the data is transmitted over two wires, one carrying the inverted signal and the other carrying the non-inverted signal. RS485 supports multi-drop communication, which means that multiple devices can be connected to the same communication bus.
BRIEF HISTORY OF RS485
RS485 was developed by the Electronic Industries Association (EIA) in the 1980s as a replacement for the RS232 standard. The RS232 standard was limited to short distance communication, and there was a need for a communication standard that could support longer distances and multiple devices. RS485 was designed to overcome these limitations and has become a popular communication standard in industrial applications.
PHYSICAL CHARACTERIESTICS OF RS485
RS485 uses differential signaling, which means that the data is transmitted over two wires, one carrying the inverted signal and the other carrying the non-inverted signal. The signal is transmitted as a voltage difference between the two wires.
RS485 uses a differential voltage signaling scheme, where the voltage levels are measured between the two wires. The voltage levels can range from -7V to +12V, with a minimum voltage difference of 200mV.
RS485 uses twisted pair cables for communication, which helps to reduce electromagnetic interference (EMI) and crosstalk. The maximum cable length for RS485 communication depends on the data rate and the cable quality, but it can typically range from 1000m to 1200m. The cable impedance should be matched to the characteristic impedance of the communication bus to minimize signal reflections.
PROTOCOL CHARACTERISTICS OF RS485
RS485 is a popular communication protocol used in various applications, including industrial automation, building automation, and transportation. It is a serial communication standard that defines the electrical characteristics of a balanced differential data transmission system.
RS485 supports full-duplex and half-duplex modes of data transmission. Full-duplex allows simultaneous transmission and reception of data, while half-duplex allows for alternating transmission and reception of data.
RS485 allows multiple devices to communicate on the same bus by using unique addresses assigned to each device. This allows for efficient communication between devices without the need for complex routing.
APPLICATION OF RS485
RS485 is widely used in various applications, including:
Industrial Automation: RS485 is commonly used in industrial automation systems to connect sensors, actuators, and other devices. It is ideal for harsh industrial environments due to its noise immunity and long-distance transmission capabilities.
Building Automation: RS485 is also used in building automation systems to connect various devices such as HVAC systems, lighting control systems, and security systems.
Transportation: RS485 is used in transportation systems such as subway and railway systems to connect various devices such as ticketing machines, displays, and control systems.
ADVANTAGES AND DISADVANTAGES OF RS485
RS485 has several advantages, including:
- Long-distance transmission capability
- High noise immunity
- Supports multiple devices on the same bus
- Low power consumption
- Low cost
RS485 also has some disadvantages, including:
- Limited bandwidth
- Limited data rate
- Requires termination resistors at both ends of the bus
- Limited transmission distance at higher data rates.
Overall, RS485 is a reliable and cost-effective communication protocol that is widely used in various applications. Its noise immunity and long-distance transmission capability make it ideal for industrial and building automation systems.