Why won't my MicroServo run at external 5v power supply? , I've tested my power supply and can light up 1 LED and also run the servo mainly on arduino and it works just fine. Im currently using a computer power supply using the red wire(5v). I'm not very knowledgeable with voltage and stuff and im hoping someone can answer. enter image description here

and here is my power supply... enter image description here

I've checked the power supply terminals but nothing is wrong there. Also, i've tried 10k potentiometer to be supplied by it but when i read it in serial.begin it just reads "0, 0, 0, 0, 1023, 1023, 1023, 1023" over and over again. Sorry about the formats im still new.

  • are you trying to power the servo by using only one wire connected to the power supply?
    – jsotola
    Jul 8, 2021 at 3:31
  • Im using ground and red wire to connect to servo and yes using power supply to power the servo
    – Exes
    Jul 8, 2021 at 3:59
  • even adapters that supplies 4.8v volts still won't power
    – Exes
    Jul 8, 2021 at 4:25
  • 1
    Did you connect all grounds? You might want to show us your circuitry. Jul 8, 2021 at 8:28
  • Or take a picture of your project such that it is clear how components are connected. That is, a picture where it is clear where all the wires are are going.
    – st2000
    Jul 8, 2021 at 12:38

1 Answer 1


The image you uploaded shown quite clearly that you have not connected the grounds between the Arduino circuit and the servo circuit. In order for it to work, the servo should reference the signal line to ground, currently only PC power supply is providing ground, so the Arduino signal line is floating.

Check out the attached image and connect the GND as shown in dotted yellow line.

Connect grounds

  • Oh wow , it works now. Didn't know about that, I thought as long as the GND and +5 of servo must be connected to power supply terminals it'll work. Im learning new things thanks alot
    – Exes
    Jul 11, 2021 at 0:48
  • You are welcome, you can also mark the answer so it will show as solved your issue.
    – Nino
    Jul 11, 2021 at 7:32

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