External Drivers - curious about DM542

I’ve been delving a bit more in to the CNC design world and I’m curious about experimenting with a different driver like the DM542.

I know the TB6600s are inside the Longmill Longboard. Is there anyway to bypass the TB6600 and access the motor control signals externally or from an internal header for testing?



You can find schematics for the board here: https://sienci.com/dmx-longmill/open-source-and-modifications/

If you wanted to use another driver system I would probably recommend finding a GRBL breakout board like this (https://www.tindie.com/products/ron/st25-arduino-grbl-screw-terminal-breakout-board/) as it will probably be a lot easier to do the wiring, and you won’t have to break or modify a working LongBoard.I’ve used this board from Tindie a lot for my own personal experimentation.

1 Like

Great, thanks Andy.

While I’ve got you, the other thing I was going to do was source a 36V PSU and give that a try. I believe it would just be plug and play other than putting the correct connector on it. Is that correct?


Using a higher voltage power supply can increase the top end torque and may allow you to run faster rapids. You can find more info about the voltage and torque relationship for steppers online.

Running more power through the controller may cause your controller to heat up more, so you may need to use some sort of active cooling (aka a fan) to keep your drivers cool.

I would make a disclaimer that if you plug other power supplies that aren’t from Sienci Labs into your controller and you break it, it won’t be covered under warranty.

The controller and drivers are specced to 48V max (although your voltage regulator might have a hard time going down to 12V from there), so theoretically you should be able to 32V.

In terms of this being a performance mod, I would probably say it’s not worth doing as increasing your top end speed may not make much of a difference in the overall cut times as your other limitation is going to come down to the rigidity of your machine. You might go faster but decrease your reliability.


I’m confused. The voltage regulator is the one inside the Longboard assembly? If the Longboard is spec’d to 48V then why would the voltage regulator be a concern?

I may not even do this, and if I did it wouldn’t be 48V but I am curious what you are referring to.


There is a voltage regulator that turns the incoming voltage from the power supply to 12V as one of the periphery outputs (for fans or other 12V low current hardware). It is not part of the driver system.

If you don’t have anything plugged into it, you shouldn’t have to worry about it.

1 Like

Ah that makes more sense. And nope, nothing on that line.