Servo Motor Moves Weakly When Powered by 9V Battery

Other Hardware Motors, Mechanics, Power and CNC
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The Servo Motor Moves Weakly When Powered by a 9V Battery
Hi everyone,

I uploaded my code to an Arduino Uno using the Arduino IDE. When I power it via USB, my servo motor works fine. However, when I unplug the USB and connect a 9V battery (through the DC jack), the servo barely moves.
My Setup:

Arduino Uno
SG90 (or specify your servo model) servo motor
9V battery connected to the Arduino’s DC jack
Servo powered from the Arduino’s 5V pin
Issue:
The servo moves weakly or not at all when running on the 9V battery.
Works fine when connected via USB.

My Questions:

  1. Is a 9V battery sufficient to power the Arduino and servo?
  2. Should I use an external power source for the servo? If so, what’s recommended?
  3. Is there a better way to power both the Arduino and the servo without issues?

Thanks in advance for your help!

2

Welcome to the forum

That depends on the type of battery. I would guess that you are using aPP3 which cannot provide the required current to drive the Arduino and servo

Yes. 4 AA cells in series works well

See the previous answer

3

Some numbers:

  • If memory serves, a typical 9V PP3 battery is designed for a 15mA load.
  • Even a Uno R3 alone requires 45mA.
  • The stall (starting) current for an SG90 is around 650mA.
4

So that means, I need to use a battery that has voltage that is higher than 9V?

5

Absolutely NO!

Your servo needs more CURRENT, not VOLTAGE.

The SG90 is rated for 4.8-6V. If you try running it off a PP3 battery the only reason it may not die immediately is that the battery's voltage will sag when so much current is demanded.

This isn't even electronics, this is electricity 101. It's literally first year high school or earlier material.

6

Ok understandable but why does my DC motor work then? Do you have any suggestion or solution for my servo motors then?

7

I generally leave a topic when it gets to the "but why does XXX work then?". It's comparing apples and oranges and it's a good indication that everything that follows will be "yes, but..."

8

Like I have to create a robo-car that goes over 5 survey lines, and the battery seems to be the problem here. I am not sure what to do and what to use. Any suggestions?

9

Use an appropriate battery, like one designed for radio controlled racing cars.

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