Computer Hardware Interface wireless rs485
RS232 to RS485 Converter rs485 protocol and RS422 Interface Circuit |
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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.
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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.
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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.
- RS232 to RS485 Converter sample Diagram - rs485 pci
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RS232 Devices |
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RS485 Devices |
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RS485 RS232 RS422 Comparison
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| RS485 Wiring 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 |
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RS485 Computer hardware interface
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Computer Interface Directory
