Grbl Shield LEDs stay lit

Hello all,

I purchased a Shapeoko2 just before the x-carve was released and it works great. I have a question about the 3 green LEDs on it for each motor. They stay lit as soon as the board receives power and only flicker when the motors are moving. If the motor isn’t moving, the LED is lit. This behavior is the opposite of every image or youtube video that I’ve watched about the Shapeoko2.

I’ve double and triple checked my wiring and it is all good and the motors move as they are supposed to and my projects look exactly as I expect them to.

Any thoughts/ideas about why they are staying lit? Is it ok that they are?

Thanks for any help!


Check the step idle delay in your grbl settings. The default setting is 255 which keeps the steppers energized to lock them in position. Any setting other than 255 releases the steppers by removing power to them. I have mine set as below:

$1=50 (step idle delay, msec)

I have the same thing happening with my Gshield. I didn’t realize it was an issue.

I prefer to keep $1=255. This keeps power to the stepper motors while the X-Carve is powered…allowing me to change bits without any danger of moving the spindle.


Take a look at this thread:

Thank you for the replies, I really appreciate them!

Bill: I’ll check the setting, thanks for the heads up!

Larry: Thank you for the link. I’m thinking if I reverse a couple of the wires, say the black & green, then I should see the behavior where the LEDs are off until the motor is moving.


Am I understanding correctly that the state of the green LEDs does not matter so long as the machine operates normally?

Yes, if your machine is functioning properly, then the state of the LEDs doesn’t matter.

If the LEDs are on, the motors have power applied, so they will heat up and so will the drivers. Setting $1 to something other than 255 turns the power off to the motors, reducing the heat generated. The downside to having the power turn off is the axes aren’t locked solidly; however, I’ve never had a problem doing a bit change in that condition.

When the LED is on, one of the phases has voltage present, depending on the setting of the “dir” control. If “dir” control is reversed then the LED is off but current flows through the phase in the opposite direction from when the LED is on. The LED is also off when no voltage is applied to the phase with the LED in the circuit.

So, as it stands your statement is correct, but doesn’t tell the whole story.