[daniellyall]

a couple of questions on the g540 im running 3v 2 amp steppers what size current set resistor would i use.
also on start up do i power up the g540 before powering up computer or does it not matter im new to all this sort of stuff so help will good.

[762x51]

Take a look at the G540 manual that you can find here:
Support

STEP 4: CONNECT MOTORS

Wire your motors to the included DB9 solder cup and secure the backshell connectors. If your motors are rated below 3.5A you must use a current set resistor across PIN 1 and PIN 5. The resistor is calculated by taking the current in amps and multiplying by 1000. If your motor is rated at 2.8A per phase you will have to use a 2.8K 5% 1/4W resistor. If your motor is rated at 3.5A or above you can safely not use a current set resistor; however, your G540 will not go into current standby mode which will result in increased motor heating.