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Topic: Powering SG90 Servo Motors (Read 3056 times) previous topic - next topic

harrywarbs

Hello,

I am designing a robot it has a total of 17 SG90 micro servo motors (data shown below). These may all be needed to move at the same time, but I could get away with only 9 motors at the same time, with the others powered, in a fixed position.

I am struggling with battery size/how many to use to power these motors. There is also an Arduino mega and a few low power sensors. I'd rather use AA or 9v batteries.

Also, if anyone could explain how they got to their answer with some calculations that would be great. Thank you, any help will be appreciated.

Working voltage 4.8-6V
Working current 0.2-0.8A

- harry

slipstick

The maximum current of an SG90 is the stall current, usually stated as 650mA. So in theory 17 of them may need up to 11.05A. In practice it's unlikely that all 17 will be starting up or stalled at the same time so a bit less than that will probably do, say 8A.

Now comes your problem. I don't know of any AA batteries that can reliably deliver that sort of current. The best you'll find are NiMH rechargeables (Eneloops etc) but they generally start to sag at much over 5-6A. They might be worth a try if you really need AAs. Of course if you have the room you could split the servos into groups and use more than one 4 pack of AAs to power them.

But for real current delivery you either need a different size battery e.g. Sub-C as were common for RC cars or a different chemistry like Lipo or LiFePO4. The problem with the latter is they are not available in a suitable voltage for SG90s.

Steve

zoomkat

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