Arduino uno Grbl dm542

Hi i have a mach3 controller for my cncest and have bought everything to build a grbl controller. I have an arduino uno and 3 dm542 and a 24v power supply for the stepper motors among the items I bought but I am not sure if I need a 5v supply for the uno. If i use a 5v supply for the uno will it cause problems when the uno is plugged into the usb as it will then have 2 x 5v supplies. I did download a wiring diagram with a 5v supply being used but im not sure it needs it. From the uno it will be running 3 x dm542 steppers and a pwm control for a 48v spindle controller that I will also link the negative of the controller to the arduino uno 5v. Thanks for any advice.

The dm542 logic inputs are optically isolated from the power.

Also, the uno should just not use the 5V from USB if you are already supplying it from the pins or barrel connector. Here’s a forum post about how it protects against potential problems in this case:

You will need some sort of 5V supply for the Arduino if it is not always connected to and powered from USB. The max recommended voltage for the barrel jack is 12V so you shouldn’t just hook up 24V to it.

Want to share a schematic of your current plans?

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You should be able to find lots on the web about powering with 5V eternal vs 5V USB but my $0.02 is to power it externally with a well regulated 5V supply( or a good DC-DC off the 24V ) and having the E-Stop kill the power. Then you should take a USB cable, cut it open somewhere and cut the red 5V wire so that your computer 5V from the USB does not power the UNO via the USB bus.

Mark the USB port on the UNO or hotglue the cable to the UNO or something which prevents you from plugging any other cable into the UNO unless you REALLY REALLY need to and know to remove the VIN 5V.

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This is not necessary or desirable. The Uno has an isolation circuit.