RS232 TO RS 485 INTERFACE
In some application plc will connected with more than 100 m cable or more. This condition will caused the data transfer need buffer to reach the source. In some application we must installing interface to avoid this problem. One of them are RS232 TO RS 485 interface.
With this converter we can connecting module PLC and HMI interface until 1200 m with coaxial cable. A multidrop system of eight drivers and receivers can be configured. The maximum common mode voltage between each additional drop is the RS422 standard of +7 Volts to –7 Volts. The driver output must be capable of ± 2 V minimum into 100 ohms. The driver output impedance must be at least 120 K ohms in the high impedance state. The receiver input resistance is 12 K ohms or greater. Receiver sensitivity is ± 200 millivolt.
Multidrop Connections
In the multidrop configuration, the host device is configured as the master and one or more PLCs are configured as slaves. This method can be used when the maximum
distance between the master and any slave does not exceed 4000 feet (1200 meters). This
figure assumes good quality cables and a moderately noisy environment. A maximum of
8 slaves can be connected using RS422 in a daisy chain or multidrop configuration. The RS422 line must include handshaking and use wire type as specified in the “Cable and Connector Specifications” section. This is electronic diagram RS 232 to RS 485 coverter:
In some application plc will connected with more than 100 m cable or more. This condition will caused the data transfer need buffer to reach the source. In some application we must installing interface to avoid this problem. One of them are RS232 TO RS 485 interface.
With this converter we can connecting module PLC and HMI interface until 1200 m with coaxial cable. A multidrop system of eight drivers and receivers can be configured. The maximum common mode voltage between each additional drop is the RS422 standard of +7 Volts to –7 Volts. The driver output must be capable of ± 2 V minimum into 100 ohms. The driver output impedance must be at least 120 K ohms in the high impedance state. The receiver input resistance is 12 K ohms or greater. Receiver sensitivity is ± 200 millivolt.
Multidrop Connections
In the multidrop configuration, the host device is configured as the master and one or more PLCs are configured as slaves. This method can be used when the maximum
distance between the master and any slave does not exceed 4000 feet (1200 meters). This
figure assumes good quality cables and a moderately noisy environment. A maximum of
8 slaves can be connected using RS422 in a daisy chain or multidrop configuration. The RS422 line must include handshaking and use wire type as specified in the “Cable and Connector Specifications” section. This is electronic diagram RS 232 to RS 485 coverter:
Description of Miniconverter
The Miniconverter consists of an RS422 (SNP) to RS232 Miniconverter, a 6 foot (2 meter) serial extension cable, and a 9pin to 25pinConverter Plug assembly. The 15pin SNP port connector on the Miniconverter plugs directly into the serial port connector on the PLCs. The 9pin RS232 port connector on the Miniconverter connects to an RS232 compatible device. When used with an IBM PCAT, or compatible computer, one end of the extension cable plugs into the Miniconverter’s 9pin serial port connector, the other end plugs into the 9pin serial port of the computer. The Converter plug (supplied with kit) is required to convert the 9pin serial port connector on the Miniconverter to the 25pin serial port connector on the IBM PCXT or PS/2 Personal Computer.
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