Walfront RS232 to RS485 Serial Converter Passive Converter Adapter Communication Data Interface Networking Supplies

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In contrast to EIA-485 (which is multi-point instead of multi-drop), EIA-422/V.11 does not allow multiple drivers but only multiple receivers. Okay, so how do you connect a RS232 to RS485 converter? The RS232 to RS485 converter can be used for point-to-point connections (connecting one RS232 to RS485 converter directly to another RS232 to RS485 converter) and point-to-multipoint networks (connecting one RS232 to RS485 converter to multiple RS232 to RS485 converters. The RS485 converter interface uses two wires for communication, one for transmitting and one for receiving data, which is referred to as a half-duplex communication converter. The typical common-mode voltage range for a RS485 converter is -7V to +12V. The serial RS232 to RS485 converter and RS232 to RS422 converter units, also called serial converters, are small electronic devices used to convert a serial RS232 signal, (for example the COM port in older computers) into either RS485 or RS422 signals. The typical serial converter does this in both directions which is also referred to as a bi-directional converter. The advantage of the RS485 protocol is that this it can transfer data over longer distances, up to 4000 feet, and have up to 32 nodes per single network, and it can be used for multi-point networks where multiple serial devices are setup in a bus network.

In some cases, if the communication distance is long (above 1000 feet) and if the baud rate is over 115kbit it is recommended to put a resistor (typically 100 ohm) at the RS485 node (across the A and B lines). Adding the termination resistor does however

How to choose the right RS232 to RS485 converter.

The RS485 Master could be a computer and the slave could for example be a camera. As you can see the data lines A- and B+ are simply connected to the RS485 Slave's A- and B+ respectively. The converters will communicate with only A- and B+ connected, however it is very important to also connect the ground wire in the finished system to establish a steady reference point to prevent data loss and other bad things. When shopping for a RS232 to RS485 converter you should first determine if you need an industrial strength or a commercial/consumer grade converter, this depends on which environment you plan to use the converter. Next you should determine if you need and isolated or non-isolated converter, where after you can decide if you need an externally powered converter or if you can use a port-powered converter. Next you can find the connector type you need, either DB9 or DB25 connectors, terminal screw header, RJ11 connector or a combination hereof. Finally you should decide if you want LED lights for the TX/RX lines, this can be very helpful when troubleshooting.

RS485, also known as TIA/EIA-485 is a standard serial communications protocol defining the electrical characteristics of a serial converter, drivers and receivers for use in balanced RS485 digital multipoint systems. Even RS485 is not commonly as popular as RS232 it is extremely useful for converters in industrial and commercial environments. A RS232 - RS485 converter is often used in industrial data acquisition and control applications where multiple serial devices communicate with each other through a converter. A non-isolated converter usually only have a simple protection against static electricity and low-voltage spikes. A RS232 - RS422 converter is a 4-wire, full-duplex, differential protocol with multi-drop capabilities and a recommended distance limit of 4000ft. ANSI/TIA/EIA-422-B is the American national standard for the RS422 protocol. What is called 'Automatic Send Data Control', which controls the data flow, is strongly recommended for most applications and devices, this feature is built into most modern RS232 to RS485 converters.

What is a RS232 to RS485 converter?

Examples of uses for a RS232 to RS485 converter could be for connecting cameras, scales, meters, scanners, PLC's or most other industrial equipment to a computer. The RS422 converter is used for data transmission, using balanced or differential signaling, it is mainly used in industrial and commercial environments since lots of process equipment and machinery have this protocol built-in. The RS232 - RS422 converter is also often used in older serial devices such as older PLC's and terminal equipment. Some of these converters can convert from RS232 to both RS485 and RS422 however many standard models only has one of the protocols. RS232 to RS485 converters can be either isolated or non-isolated. An isolated RS232 to RS485 converter have optical isolators separating the data lines inside the unit, this prevents noise, high voltage spikes, surges and ground-loops from damaging your computer or the equipment you have connected to the converter. Some RS232 to RS485 converters even have the externally power supply isolated from the rest of the converter to provide additional protection. Usually isolated converters are only used if the user wants to additionally protect the equipment connected to the network (in case the equipment is of high value), or if there are reasons to suspect high voltage spikes or similar in the network.

is also fairly resistant to noise which is one more reason why it is favored in industrial environments. The RS232 to RS485 itself, regardless of what model you choose, is simply a device which can convert standard RS232 data signals into RS485 signals and vice versa. Most RS232 to RS485 converters can convert data in both directions, from RS232 to RS485 and from RS485 to RS232, this is also called a bi-directional converter. Some RS232 to RS485 converters are powered from the computer's COM port (usually from either TX, RTS or DTR), others need an external power supply to work. Even with port-powered converters you should in most cases be able to communicate up to the specified 4000 feet, however adding a terminal resistor can interfere with this distance because it increases power consumption. We will here not go into the specifics of how the RS232 or RS485 protocol works, but if you are interested in this then there is lots of RS232 and RS485 information on Wikipedia, including how a USB to serial adapter works. We will however demonstrate the most common ways of connecting a RS232 to RS485 converter.

RS232 to RS485 Circuit Schematic

dramatically increase power consumption so it should not be done, and is mostly not needed at shorter distances. Due to the increased power consumption termination is also rarely done when using port-powered converters.