Experiencing servo jitter when powered from AC adapter

Other Hardware Motors, Mechanics, Power and CNC
1

Hello!

I am working on a project that involves controlling 5 servos with an Arduino Uno. Up until now, I have successfully been able to control one servo motor when it is connected to the Arduino for power, and the Arduino powered via the USB cable (pictured in powerArduino.jpg)

Before getting to all 5, I am trying to power one servo using an AC adapter since I've read that the Arduino won't be able provide enough power. But when I connect the motor to the external power source, the motor starts jittering pretty erratically. The Arduino is still powered by the USB cable (signal pin is disconnected for the photo so that motor stops moving) (pictured in powerAdapter.jpg)

Can anyone help me troubleshoot this? I'm pretty new to circuitry but I didn't think I'd have an issue with this setup since the AC adapter supposedly provides enough voltage and current. Here's a summary of the project specs:

  • Arduino Uno (powered by USB connection to computer)

  • Longruner LKY62 servo motor

  • Operating voltage: 3.0V-7.2V

  • Operating current: 500mA-900mA at 6V

  • Does this mean the motor needs 6V even though the operating voltage is listed as having a wider range?

  • AC adapter wall plugin

  • Output voltage: 5V

  • Output current: 2.5A

powerAdapter.jpg
powerAdapter.jpg1000×750 275 KB

powerArduino.jpg
powerArduino.jpg1000×1112 376 KB

2

You need a wire from the servo - (negative, brown) to Arduino GND,

3

That is evidently the MG996R servo, with a stall current of 2.5 Amperes.

The power supply needs to be able to handle the stall current for as many servos that will be moving at once, so the power supply that you have is marginally adequate for just one servo.

4

Thank you, I didn’t know about the difference between stall current and running current. So to operate all 5 load-bearing motors I’d need 2.5A x 5 = 12.5A of current, right? Is there a way to increase the output of the adapter?

Also for the servo’s ground wire, do I need to connect it to both the power source’s negative terminal and the Arduino GND?

5

Is there a way to increase the output of the adapter?

No.

Yes, always connect all the grounds.

6

Thank you! Grounding the Arduino as well solved the jitter. Now I just need to find a good power source...

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