[51] max 485 in noisy environment

[unbhandari]

i am working with max485 for rs 485 4 wire system with modbus protocol. i found loss in serial connection when ac servo drive goes on. can any one help in this regards?

 

[Bovsov]

Any scematic?

 

[Gorgon]

4 wire RS485?
Do you have power supply for the circuit in the cable too?

 

[embpic]

is it full duplex mode??
you must use 120 ohm resister between differential line.

 

[Gorgon]

Since you said you used a MAX485 driver, I assumed you used half duplex, since that driver is a half duplex driver only.

If you have 4 wires and want to use a full duplex communication you may need to switch driver chip.

If it is full duplex RS485 you need to terminate with 4 x 120 ohm resistors, 2 resistors in each end of the cable.