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I wish to power an Arduino Uno board AND 3 servo motors using a single 9 V battery.

I have connected the positive terminal of the 9 V battery to the VIN pin. The negative terminal of the battery is connected to the GND pin immediately following. This, I believe, powers the Arduino Uno board.

Next, I have connected the power wires of all 3 servo motors to the 5 V pin on the Arduino board ( using jumper wires and a breadboard). Similarly, all the servo ground wires have been connected to the second GND pin in the 'POWER' set of pins on the Arduino Uno board. And finally, the 3 signal wires from the servos have been connected to the three PWM pins on the 'DIGITAL' row, exactly pins 9, 10 and 11.

THE SERVOS ARE NOT OPERATED SIMULTANEOUSLY, THEY ARE BEING OPERATED ONE-BY-ONE (but the load is still attached to each of them, a couple of grams is all).

Since the servo motors operate between 4.8 V - 6 V, and I don't have any spare AA batteries to approximate a 6 V battery, I thought this could solve the problem.

My question is, does this pose any problems for the board or devices, does this draw a higher current? Will it damage the Arduino Uno board or the servo motors or any of the individual pins?

Please let me know soon, thank you very much.

  • Do you have any of the specifications for any of the things you are connecting? – Ignacio Vazquez-Abrams May 27 '16 at 20:52
  • @IgnacioVazquez-Abrams. Servo motor specifications: Operating voltage: 4.8 - 6 V. Operating speed: 0.2s/60 deg (at 4.8 V), 0.16s/60 deg (at 6 V). Stall torque: 3.8 kgcm (at 4.8 V), 4.5 kgcm ( at 6 V). Temp range: 20 degC - 60 degC. Is this what you were asking for? – Ram Sidharth May 28 '16 at 6:01
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I don't think anything should get damaged; the regulator is rated for 1A, and even beefy servos don't draw more than 200mA when moving against heavy load. The problem is that your battery won't last long. Even the heavy-duty Li primary 9V batteries are under 1000mAh, and the actual capacity is heavily dependent on the discharge rate.

Why can't you use a rechargeable Li-ion pack with an appropriate step-up or step-down converter?

  • I do have a rechargeable 9V Li-ion battery. Are you talking about a DC-DC converter? Isn't the Arduino's voltage regulator enough? Can you please explain why you suggested that setup. Thank you. – Ram Sidharth May 28 '16 at 5:55
  • I'm sorry, since my question wasn't clear on this point. The servos are not being operated simultaneously, they're being operated one-by-one. In such a case, wouldn't the battery last longer than otherwise? If so, could you explain why? Thank you. – Ram Sidharth May 28 '16 at 12:22
  • The 5V regulator on the Arduino is a linear regulator, not a switching regulator. In any case, you probably won't damage anything. Just connect it up and see how long it lasts, and whether that's enough for you. – JayEye May 28 '16 at 15:39

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