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I've only started using Arduino in the last week, and I'm having a problem with the servo supplied with the kit I purchased. It's a SG90 microservo. I'm trying to connect the servo as shown on the Arduino tutorial site:

enter image description here

But when I connect the power and ground pins to the board, the board powers down and disconnects from the USB. I've had the servo working before without a problem.

Yesterday I was trying out another tutorial without any luck, and I noticed the servo getting hot (not too hot to touch though).

Could I have accidentally fried the control board in the servo?

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  • Probably. It sounds like it's causing the power to short. – Majenko♦ Feb 11 '18 at 22:55
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    Never run power to a servo or other motor through an Arduino or from its regulator. Also do not power servos from USB. – Chris Stratton Feb 11 '18 at 23:47
  • @ChrisStratton Nice information. I think I do that mistake for several times. Cares to elaborate? – dhimaspw Feb 12 '18 at 1:18
  • @ChrisStratton I don’t think I did. What would that look like? – Jim421616 Feb 12 '18 at 1:47
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    Oh! But that schematic is from the tutorial! – Jim421616 Feb 12 '18 at 18:04
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Have a look at the current requirements of the SG90 and compare this to the maximum current available from an Arduino Uno.

enter image description here

Another thing to look at is how much current your computer's USB port can supply. My laptop, for example, can only supply 500mA per USB port.

My advise is to use a separate 5V power supply for the servo.

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  • So the technique I used should be ok if I power the board with a 9V battery rather than through the USB? – Jim421616 Feb 12 '18 at 19:52
  • There's a couple of problems with that idea. If you are talking about an everyday alkaline 9V battery with an approximate mA hour rating of 580, and you draw the SG90's "running current" of approximately 270mA from it, how long do you think the battery will last? – VE7JRO♦ Feb 12 '18 at 21:04
  • If your Arduino has a AMS1117 voltage regulator, then it's maximum power dissipation specification is 1.2W. Supplying 9V at the power input jack will give you a maximum output current of approximately 360mA. (9 - .7 - 5) * .360 = 1.19W. The "stall current" of the SG90 is up to 730mA, more than double the current you have available. A separate, 1A, 5V power supply is what I would use. – VE7JRO♦ Feb 12 '18 at 21:05
  • I'm sorry to harp on about it, but pretty much all of the tutorials I've been able to find online suggest hooking up the servo in the way I originally posted about. I guess maybe I hooked it up incorrectly, but as far as I can tell, you're all advising against this method anyway. So I'm confused; is this a good way to hook up the servo, or not? And if not, what would the best way look like in a schematic? – Jim421616 Feb 13 '18 at 5:00
  • Unfortunately, there are several tutorials on the internet showing the servo connected directly to an Arduino Uno, which is incorrect. Here is a tutorial with a connection diagram showing a separate power supply for the servo in Step 3: instructables.com/id/… – VE7JRO♦ Feb 13 '18 at 9:36

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