View Full Version : G540 Current set resistors

18-08-2010, 01:40 PM
I was wondering if anyone can help me with the current set resistors on my G540?
From what i can gather they are used to limit current to the motor but there is also a 3.5A max per channel anyway.
My x & y motors are rated at 3.5A. My z is rated at 4.3A so do i need to use a current set resistors or not? :confused:


18-08-2010, 04:23 PM
Hi Wayne,

The instructions for the G540 doesn't say you can't have a resistor so I guess you do need one. They are set up for an output current of 1A per kohm of resistance, so I read it as you need a 3.5kohm (3.3k + 220R in series). The limit of 3.5A is the maximum safe working limit for the stepper driver, I suspect it will actually go a little higher than that and if you leave the resistor off it will default to some value just above 3.5A, however that may not be a safe operating mode.

23-08-2010, 02:17 PM
The G540 has idle current limiting which reduces the current at idle to 70% of whatever has been set via the resistor value.
If there's no resistor, then current limiting is disabled.
End result is that without current limiting, the motors will run hotter.

23-08-2010, 02:21 PM
Thanks Guys, I guess they are worth using then although its good to know there's no danger to motors / drivers until i get them sorted :tup: