Need advice building an animatronic eye

Hello: I’m new here so I hope I am in the right spot. I’m putting together an animatronic eye using Will Copley’s design: Notion – The all-in-one workspace for your notes, tasks, wikis, and databases.

This build uses Arduino Uno and a servo driver. In his tutorial, he shows a USB printer cable attached to the UNO. This is used to upload code of course but it is also used to power the UNO. The servo board used a separate 5V power supply. While using a printer USB cable works for setting this up, I do not want to use it normally. Also, I don’t understand why 2 power supplies are needed? So, I plugged in a 12V power supply into the UNO and routed 5V from the UNO power pins to the servo board. Now only about half of the 6 servos work. I then put the power back to the separate 5V supply and now nothing works.

I don’t understand why this does not work? The servo motor takes 5V, I confirmed that the UNO 5V pin is actually 5V. The UNO board can use a 12V power supply. I looked it up! I tried re-uploading the code with no luck. I rechecked the wiring as well.

What am I missing here? I ordered a new Arduino UNA and a servo board but don’t want to blow them up too (if that’s what I did).

Use a separate, adequate 5V power supply for the servo board. The power supply must be capable of supplying at least 2-3A or more depending on your servos’ requirements.

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Thank you for getting back to me. So, if I understand you correctly, I need to use 2 power supplies, 1 for the servo board and one for the UNO. Is that correct?
Also, should the power supply for the UNO also be 5V or should 12 V work ?