PLC Communication Protocols

Profibus

What is Profibus?

Profibus (Process Field Bus) is a standard for fieldbus communication in automation technology. It is used to connect various devices and systems in industrial automation environments. Profibus allows for real-time communication between devices like sensors, actuators, and controllers.

Devices Connected:

• Maximum Devices: Up to 126 devices can be connected on a single Profibus network.

Range:

• Distance: Up to 1,200 meters (1.2 km) for Profibus DP (Decentralized Peripherals), depending on the baud rate.

Voltages:

• Minimum Voltage: 9 V DC.
• Maximum Voltage: 32 V DC.

Profinet

What is Profinet?

Profinet is an Ethernet-based protocol for industrial automation. It integrates field-level communication with the higher-level enterprise systems and provides real-time data transfer. Profinet supports a wide range of devices and applications, including both real-time and non-real-time communication.

Devices Connected:

• Maximum Devices: The number of devices is theoretically unlimited but practically limited by network design and performance.

Range:

• Distance: Limited by Ethernet standards, typically up to 100 meters for standard Ethernet cables, but can be extended using network switches and fiber optics.

Voltages:

• Minimum Voltage: 9 V DC (depends on the specific Profinet device).
• Maximum Voltage: 32 V DC (typical for industrial Ethernet devices).

RS-232

What is RS-232?

RS-232 (Recommended Standard 232) is a serial communication protocol used for point-to-point communication between devices. It is commonly used for connecting computers to peripheral devices such as modems and serial ports.

Devices Connected:

• Maximum Devices: Typically connects two devices (point-to-point communication).

Range:

• Distance: Up to 15 meters (50 feet) at a maximum baud rate of 115200 bps. Distance can be extended with lower baud rates.

Voltages:

• Minimum Voltage: -15 V DC.
• Maximum Voltage: +15 V DC.

RS-485

What is RS-485?

RS-485 is a standard for serial communication that supports multi-point systems. It is used in industrial environments for long-distance and high-speed communication between multiple devices.

Devices Connected:

• Maximum Devices: Up to 32 devices per network segment (transceivers), though this number can be increased with the use of repeaters.

Range:

• Distance: Up to 1,200 meters (1.2 km) at lower baud rates. The range can vary depending on the baud rate and the quality of the cable.

Voltages:

• Minimum Voltage: 7 V DC.
• Maximum Voltage: 12 V DC.