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Board detection and Lightburn re-homing differences between MG2 and MG3.

I recently replaced my MG2 board with an MG3. I had a separate 24V power supply for my steppers on the MG2 and that wiring setup carried over to the MG3.

On the MG2, I could turn off the power switch on the K40, which would drop the connection to the computer and disable the motors so I could manually move the gantry as needed, then turn it back on. The computer would see it reconnect and know to rehome.

The main issue I'm having is that the MG3 does not behave in this manner at all. If we forget to rehome it after powering off the motors and back on, then try to cut, it will force the head out of bounds. Is there a way to get this behavior back?

At first, I thought maybe the USB on the computer may be keeping the board powered up, but when I used an inline USB power blocker, that completely blocked communications from the board to the computer.

dancolwp1974 has reacted to this post.

Hi Derrick,

the good news is that there's an easier way to lock/unlock the gantry, it actually works for both MG2 and MG3. In the Lightburn console, you can:

set $1=100 so motors don’t lock while in rest.

set $1=255 to return to normal motor operation.

For maximum user friendliness, you can set up macro buttons so that there's a single button for Unlock and Normal modes. Follow the same process as explained in this link, except the macro contents is simply just the $1 settings.

Does this help?



Did not work. The gantry is still locked. Also, I still want to find a way for it to just auto home if the power to the laser is turned off and then back on again, which is the main issue.

Hi Derrick, The MG3 differs from MG2 in a way that the power circuits are not shared as in MG2.

MG3 uses a hot and cold side (5V and 24V DC power). The cold side is the USB comms / PC side. The hot side is the PSU laser side (24 and 5 V DC). What you can do to make the hot power connection side switch with the cold side is to add a relay. When the cold side has 5V then it would switch the 5V/24V connections on the hot side via a relay. I assume that just switching 5V on the hot side would be sufficient to get the steppers out of locked mode. So you might not need to switch the 24V at all. If you have some spare step sticks, you could cut off the 5V pin header and wire that to a relay switch to test it out.

Let me know if you have any questions or need a schematic.

Cheers Paul

Cheers, Paul awesome.tech

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