I've looked around, questions not exactly covering what I am looking for... except maybe this... but it suggests splitting cables.
Setup:
Arduino UNO with USB to PC
12v 2a PSU with Barrel Jack
CNC Shield
Query:
Is it safe to put 12v into the barrel jack of the UNO, then solder two wires up to the CNC shield and power that via the barrel connector ? I know the CNC power and uno's grounds have continuity... I'm wanting to ensure there's no issue with the power supply.
I have done this: it does work, but I'd like to double check if it's a safe, reliable solution that will not burn out either board in the long run. I am using this method for ease of attachment for the user to access a single barrel connector.
I understand shield takes 12-36 v and Uno barrel jack takes 7-12v
There is a diode between the power jack and Vin. It is rated at 1A. Most likely your steppers draw more than 1A so powering via Vin through the power jack could blow that diode.
Be careful when using the power plug or Vin. Powering through Vin or the power jack means that the Arduino and all peripherals that are on the 5V rail are powered by the onboard 5V regulator. The on board 5V regulator is not heat sinked so will supply limited current before it overheats and shuts down. The amount of current depends on the voltage input to Vin or the power jack. The higher the voltage the less current can by supplied. I would use a buck converter to drop the 12V to 5V and connect that to the 5V on the Arduino, bypassing the, weak, 5V regulator. Then the rated current of the DC DC converter is available on the 5V line.
So, I do not think it a good idea to power the CNC shield off the Uno. Give the CNC shield a power supply with the right voltage and sufficient current capability to run the steppers plus some overhead. Run the Uno from USB or a regulated 5V to the 5V pin.
Dear Sir/Madam, this has got to be one of the most concise and helpful replies I could have ever asked for, you not only provided the answer but explained why and how the system works.
I will allow the Arduino to power off the USB and will purchase a mounted barrel connector and wire that directly to the CNC shield.
I am glad I asked, as you have explained why at present it may 'work'.... however if this system were used for hours many times a day it would break down ...... may explain why my old uno broke and would not read the limit switches.
Very, very much appreciated.
Answered in a few minuets of me posting, and I recognize your name as helping others years ago in the past.
