The making of a RS-385 repeater

[xxtigerxx]

I want to make a repeater RS-485 so i can go more distance.

does anyonee have any schematic?

Thanks in advice

 

[laktronics]

rs485 repeater circuit

Hi,
Refer fig.23 of this tech note from Maxim, showing the application of 485 IC as a repeater. You have to ground REbar and pull up DE in this case.
Regards,
Laktronics

 

[vdaniel]

repeater 485

Download schematic from https://www.rs485.com/pirsfc24fb.html

 

[xxtigerxx]

rs 485 repeater circuit

Thank you Iaktronic,

i will try it...

 

[FvM]

rs485 repeater schematics

To be true, I don't see how the driver should work as a repeater in the shown maxim circuit, without a logic circuit determining the data direction.

 

[laktronics]

rs-485 circuit auto switching

Hello FVM,
I think these repeaters have limitations and are meant for 4wire RS-485 or 422(one-on-one)applications only. For RS-485 applications having single master and multiple slaves, the circuit will work if all slaves are located beyond the repeater with respect to Master. If some of the slaves are located between the master and the repeater, those slaves beyond the repeater should generate a repeater enable signal while transmitting data to the Master.
Multi Master RS485 should also work so long as all masters are located on one side of the repeater.
Regards,
Laktronics

 

[xxtigerxx]

repeater rs485

Iaktronics

do you have a schematic for a RS-485 repeater
with no limitations

Added after 1 hours 23 minutes:

What do you think about these circuit?

 

[laktronics]

repeater with different baud rates

Hi,
For two wire circuits, this repeater can be used with automatic direction switching for a given baud rate. But again this circuit has a limitation in that the RC time values will change for each baud rate and a DIP switch selection will be required to select different RC values for different baud rates. Another variation of this circuit replacing the flip-flop circuit with retriggerable monshots like HC123 will have better timing control than passive RC connection shown here, but again, the time constants need be selected for each baud rate in this case also.

I think, when you are designing a system, you may not always get a universal solution for all situations and one will have to select the appropriate connections to match the system requirements.

Regards,
Laktronics

 

[FvM]

repeater ic rs485

Hello,

the Maxim solution is equivalent to the technique of commercially available products, e. g. as repeater or transparent fibre-optic bridge for PROFIBUS nets. As said, it has to be adapted to the baud rate. Also a minimal idle time of one frame length after each transmission must be guaranteed to disable the repeater/bridge reliable before a new transmission of possibly opposite direction starts.

Regards,
Frank

 

[davidgrm]

maxim rs485 repeater

what distance are you trying to go and at what speed?

 

[xxtigerxx]

rs485 + repeater + schematic

Distance is up to 700metre and 56kbaud rate

 

[davidgrm]

rs485 repeaters diy

A lot depends on what type of cable you use. I have achieved > 1000m using Cat5 twisted pair with shielding. Also I connected the gnd between the boards