Arduino to send command to motor controller.

Hi all,
I have a motor controller that needs motion commands to be sent via RS485. I also have a USB to RS 485 converter. So, If I connect this to me PC and send a command using hyperterminal the motor moves. But if I connect my Arduino to the motor controller and send the same signal from the arduino using "Serial.println" the motor does not move. What am I doing wrong here?

regards,
kaar

How are you connecting the Arduino to the motor controller?

The motor controller has a USB to RS485 converter. So I just connected the arduinos usb to the motor controller USB.

Which Arduino are you using? Unless it's a Leonardo, or you have a USB host shield, you can't connect a USB client device to an Arduino.

EDIT: Looking at the reference page, I don't think a Leonardo can be a USB host either.