9v Battery & Servo Questions

Other Hardware Motors, Mechanics, Power and CNC
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Can I use a 9 volt battery plugged directly into the Aruduino board AND have the Arduino plugged into the computer with the USB cable? I want to power two MG90 servos without using a breadboard.

Can two MG90 servos be plugged directly into the Arduino board, or not? I heard that there are two 5V pins, one labeled with 5V and another at SPI header 2.

Below is a picture of what I am talking about with the 9v plugged directly into the arduino.
https://i2.wp.com/randomnerdtutorials.com/wp-content/uploads/2013/11/ArduinoUNO_Running_From_1x9V_Battery.jpg

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2

Regardless of how you get the power into the Arduino, you can't provide enough current to a servo from the Arduino.

I found this which shows the stall current is 700mA, way too much. And you want to have two?

image

Get a decent 5-6V power supply that can provide about 2A and power the servos from that.

3

Since I posted, I found this video of two servos connected directly to the Arduino. Can the board be damaged by doing this? Would plugging in the 9v battery help at all?

4

I think the way the author spelled "internal" says it all, following this kind of trash on the internet is a sure route to destroyed Arduinos, computers, etc.
The power for the servos is coming through the USB supply on the computer (normally limited to 500mA), how many servos will it run before burning out the computer's power supply? You are trying to run two servos through the UNO's 5V regulator which, after dropping 9V to 5, can only supply about 250mA before overheating and (hopefully) shutting down. Typical servos draw around 300 to 600mA after a 1+ Amp starting surge and a puny 9V battery can only supply a few hundred mA for a very short time.

5

Hi,
The video shows the servos working with NO LOAD on the spindle, so current consumption is relatively low.
If the servo was doing some work and had to produce TORQUE at the spindle, then more current would be needed, more that a 9V battery or the 5V USB supply could pass.

Tom... :grinning: :+1: :coffee: :australia:

6

Yes

Can two MG90 servos be plugged directly into the Arduino board, or not? I heard that there are two 5V pins, one labeled with 5V and another at SPI header 2.

No
Two issues:

  1. The Arduino board must convert the 9V to 5V for the board to run. This conversion has limited current capability. The 5V pins on the board are for very low power devices.

  2. A 9v battery has very little energy. between 160 maHr and 300 maHr depending on the value of the load. At higher consumption rates you only get 160 maHr.

160 maHr means if you draw 160 ma you battery will be dead in one Hour.
If you draw 1 amp the battery will be dead in 90 minutes.

7

sp. "mAh"

8

Did you mean 90 seconds?

9

Besides the 9v battery running out of juice quickly, is there any other problem with a 9v put directly into the arduino board?
Are MG90 servos considered low powered devices?

10

Thanks for catching this. The chart I looked at shows about 3 minutes before the voltage is too low to be useful.

11

Yes
You cannot run 5V servos from the 5V output of the Arduino board. It might work for a short time making you think you're OK but the Arduino board will fail at some time. Could be 5 minutes, could be weeks.

I'm not familiar with the MG90 servo. But I would guess it has a lot to do with the load on the servo.

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