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Computer PC Hardware Interface wireless rs485

RS485 communication info

 

RS485 Sample Diagram

Picture1. RS485 sample diagram (pcinterfaceio.com)

The RS232/RS485 converter allows to interface any device using an RS232 serial link to an RS485 link. The RS485 link was conceived for long haul data acquisition and control applications. The original specifications (which have been surpassed by present hardware), allowed to network up to 32 stations on the same lines, at speeds up to 10 Mbits/s to distances of 4,000 feet (1200 mt). The link is balanced so that any electrical noise getting into one of the lines also gets into the other line thus allowing the receiver to cancel both noise signals.

db9 connector

RS-232/422/485 Pin Assignments (Male & Female DB9)

RS232 RS422 RS485 Pin

  • RS485 card links are much used in industrial process control where reliability is important. Also,the ability to communicate over a long distance at a high speed is important when it comes to industrial plants where the stations might be spread over a large area.It is very common to have a PC in charge of controlling a given process. PC's in general have an RS232 serial port (COM port) and therefore there are two solutions to link the computer to an RS485 network: One is to plug an RS485 interface in a computer slot and the other is to convert the RS232 level signal coming out the computer serial port into an
    RS485 signal. This is what the RS232/RS485 converter does. The converters are designed to work with the RMV Electronics general purpose I/O-485 line of stations specifically built for process control but they can also be used back to back thus providing anRS232/RS485/RS232.

  • This way, two computers or devices using a standard RS232 serial port can communicate with each other at a maximum of 115200 Bauds over a distance of 4000 feet, something impossible to achieve using an RS232 link. One interesting application for using two RS232/RS485 converters back to back is when a computer needs to be connected to an I/O-232 board at a distance longer than usual. This provides very good performance while keeping the simplicity of our I/O-232 line of boards.

  • More nodes can be connected using repeaters, up to the addressability limit (usually 256) of the devices used.
  • RS232 to RS485 Converter sample Diagram - rs485 pci
RS232 Devices
RS48 Process Diagram rs485 cable Wiring
RS485 Devices
 

You must use an RS-232 to RS-485 converter device or USB port to RS-485 converter, or install an RS-485 interface card in your computer. PCI bus, PCMCIA/CardBus or ISA bus cards can be used.

List of RS485 Convertor Type

RS422

rs422 circuit diagram

RS422 Circuit Diagram
(www.interfacebus.com credit)


RS485

RS485 Circuit Diagram

RS485 Circuit Diagram
(www.interfacebus.com credit)


 

RS485 RS232 RS422 Comparison

RS485 Compare SPECIFICATIONS RS232 RS422 RS485
Mode
SINGLE
-ENDED
DIFFERENTIAL DIFFERENTIAL
Total Number of Drivers and Receivers on One Line (One driver active at a time for RS485 networks) 1 DRIVER
1 RECVR
1 DRIVER
10 RECVR
32 DRIVER
32 RECVR
Maximum Cable Length 50 FT. 4000 FT. 4000 FT.
Maximum Data Rate (40ft. - 4000ft. for RS422/RS485) 20kb/s 10Mb/s-100Kb/s 10Mb/s-100Kb/s
Maximum Driver Output Voltage +/-25V -0.25V to +6V -7V to +12V
Driver Output Signal Level (Loaded Min.) Loaded +/-5V to +/-15V +/-2.0V +/-1.5V
Driver Output Signal Level (Unloaded Max) Unloaded +/-25V +/-6V +/-6V
Driver Load Impedance (Ohms) 3k to 7k 100 54
Max. Driver Current in High Z State Power On N/A N/A +/-100uA
Max. Driver Current in High Z State Power Off +/-6mA @ +/-2v +/-100uA +/-100uA
Slew Rate (Max.) 30V/uS N/A N/A
Input Voltage Range +/-15V -10V to +10V -7V to +12V
Input Sensitivity +/-3V +/-200mV +/-200mV
Input Resistance (Ohms), (1 Standard Load for RS485) 3k to 7k 4k min. >=12k

RS485 Computer hardware interface


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