Mini Servo behaves wildly

I have a mini servo connected to my Arduino UNO and I'm just getting it to move from 0deg -> 90deg -> 0deg on a loop. But it misbehaves more than occasionally when I run the code such that:

  • At the start, the servo rapidly spins 180deg and back, quite a few times before it finally 'calms down' and does what the code intended
  • Sometimes in the middle of working normally, it would also do that crazy spinning for a while

The servo is a pretty old and discontinued Parallax Standard Mini Servo. Here's its relevant specs:

Power: 4.8vdc to 6vdc max
Speed: 0 deg to 180 deg in .5 seconds on average
Weight: 26.6 grams/.94oz
Torque: 2.8 kg-cm/39oz-in

I followed this schematic diagram, except that GND and PWR were connected to a breadboard first while SIG was direct to the digital pin. The Arduino is connected by cable to my desktop and the 5V and GND are connected to the breadboard because it's also powering an LCD and sensor.

I saw one forum post where a user said that any servos in general should NOT be getting power straight from the Arduino 5V. But my servo model differed from theirs so I wanted to get my own confirmation from the community whether I am facing the same case.

Let's say it IS the case, what affordable solution would there be? If anything, I have a Raspberry Pi 3 B+ but it's only 3.3V.

That is the most likely cause of the problem. The Uno just cannot supply the current that the servo needs. A 4 AA cell battery pack is a good supply for the servo. Be sure to connect the battery pack ground to the Uno ground as well as the servo ground.

Greetings and thank you for the assurance!

Is the battery pack/holder specifically to be 4 AA because each AA is about 1.5V giving a 6V total (what the servo needs)?

I see the battery GND goes to both UNO and servo GND like you advised. But is the servo GND connected to the UNO GND as well? My apologies if I misinterpret the diagram!

From the servo specifications in your first post. 4 AA alkaline cells would be 6V so is the proper power for the servo.

Yes, all of the grounds are connected together.

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