Looking for RS485 circuit with only 2 wires

[mtawab74]

RS485 circuit

I need a circuit that uses rs485 driver where
there's only 2 wire between transimiter and receiver and those 2 wire carriers data between transimetter and receiver and also carry power from transimeter to receiver card

the receiver card operates at 8 volt and consumes 150 mA

thanks in advance

 

[kekon]

Re: RS485 circuit

Well, the problem you described may be a bit difficult to solve. There is no problem to transmit data only using just 2 wires as it is commonly used in various communication systems. Sending power supply of 150mA along with data (for long distances) using just 2 wires may introduce communication errors especially at high data rates and long distances. I recommend use of 4-wire cable where two additional wires are used only for power supply transfer. One must keep in mind not to transfer AC current as it will surely cause transmission to fail.

 

[davorin]

Re: RS485 circuit

You can try maybe with some small series transformer to modulate the powersupply with your data and extract it back on the other end with a transformer or capacitor...though you need to work in a frequency band high enough so it doesn´t get shunted by the power supply...

I would go with the hdcl capable controller from Zilog and operate with the similar protocol as Apple did once for localtalk...meaning runing at 230kbits/sec...

But maybe there´s a cheaper way?

 

[7rots51]

Re: RS485 circuit

you can communicate data up to 160 kbps for 4000 meter with MT9172 from zarlink and send power and data on two wire (awg24 wire) and there is no problem ,I tested it and works nice.(only point to point)
you can also use MT8952 chip with it for data.

 

[mtawab74]

Re: RS485 circuit

Dear 7rots51

would you please post your schematics or send it to me by email

mtawab74@hotmail.com

Thanks for all replies

 

[mtawab74]

Re: RS485 circuit

REGARDING THE SOLUTION OF USING TRANSFORMER AND CAPACITOR I USED A CIRCUIT ATTACHED BUT IT GIVES BAD RESPONSE

AND DISTURT DIGITAL DATA PERIODES AND DELAYED IT

fo example while using 9600 bit/sec ( i used clock source 9600Hz 50% duty ) the high period was about 3 times the low period even the original

and some data sent are lost

 

[arcaphill]

Re: RS485 circuit

This is the information!

 

[mtawab74]

Re: RS485 circuit

Dear all finally i got a solution
the attached files contain 4 identical circuits that contains a darlington

those circuits simulat a coil which could be adjusted to any inductance value up to 10H

i used it and it performs very good

salam

 

[binu G]

RS485 circuit

have any one have idea for rs485 interface with opto isolation.

binu g

 

[ITP]

RS485 circuit

Please see the document .
https://www.grantronics.com.au/docs/TIA-EIA-485.pdf

There is an example for Isolated RS485 Node With SN75LBC176 IC on page 13.

Itp

 

[bjxxh]

RS485 circuit

Dear 7rots51

would you please post your schematics or send it to me by email

bj_xxh@hotmail.com

thanks!!!

 

[7rots51]

Re: RS485 circuit

use msan_124.pdf and MT9092 and MT9172 and MT8940 ,msas_42.pdf,...

in www.zarlink.com ,you can easy use the fig2 of msan_124 to generate stbus signals and use mt9092 to send data and voice over cable ,you can also mt8952 as data tx in hdlc format.

the sch of mt9172 is in its datasheet ,for trans buy you can get helps from zarlink support,they introduce you a hongkong company for it.