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Topic: help on how to use 9 sevo motors with uno (Read 1 time) previous topic - next topic


hi everyone..
i m working on a project from coll and i m pretty new to arduino.. i use a arduino uno board and i want to know if it is possible to run 9 servo motors with it using servo libary 2.
and i also want to know how much external power would i have to supply to the board


Just a tip, you don't power servos thru the arduino boards. You need an external power supply for the servos.
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A typical servo motor will draw between 500mA and 1A depending on the size of the servo and how much load it is under.  In your case, you are wanting to run 9 servos so worst case of each servo running under full load you would need a 9A supply to handle this.  You don't provide any info on what your application is so its hard to determine if this is overkill or not.  Also note that the power supply for the servos needs to be a separate supply from what you are delivering to the Arduino board.  The voltage regulator on the Arduino cannot come close to regulating that much current so you need to have the separate supply for the motors and just make sure the ground for the servo power supply is also connected to the ground on your Arduino board.


Feb 15, 2011, 09:50 pm Last Edit: Feb 16, 2011, 09:08 pm by Binette228 Reason: 1

Can you give us the datasheet of your servos?

Good luck with your project and keep us informed of any need of advancement!


From the Arduino 22 reference:

The Servo library supports up to 12 motors on most Arduino boards and 48 on the Arduino Mega. On boards other than the Mega, use of the library disables analogWrite() (PWM) functionality on pins 9 and 10, whether or not there is a Servo on those pins. On the Mega, up to 12 servos can be used without interfering with PWM functionality; use of 12 to 23 motors will disable PWM on pins 11 and 12.
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Now I'm not sure what the current carrying capacity of the board itself is, but could you perhaps buy another power supply to replace the one that is supplied with the arduino board, one that can output a larger current but maintains the same voltage of the original power supply.

If this isn't possible, what would you do to connect the ground from the servo to the secondary power supply if the power supply is one of the types that is double insulated and has no earth pin to plug in the wall socket? (Yeah, we have these in Australia). Would pinching the earth from the arduino's power supply work, since it's all of the same continuity anyway?

I'm looking to do a similar thing with multiple servos in the future. I dont know what load it will be, so overkill would probably be a good idea in my case. :)

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