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I have 4 Tower Pro MicroServo 9g SG90 I want to power with a battery. This is the datasheet I found online: http://abc-rc.pl/templates/images/files/995/1428085018-sg-90-tower.pdf

I have a small breadboard and some resistors laying around (220, 1k, 10k), and a 9v battery.

I hooked up the battery leads on the power rail of the breadboard, and added my 4 servos in there, and they turned on and rotated properly when I issued commands from my Arduino board. The thing is that AFAIK it operates on 4.8v-6v from what I have read.

I did a voltage divider using some of the resistors I had and I could output 5v when tested with my multimeter, but the servos didn't work (probably because low current).

So my question is, can I power my 4 servos with a 9v battery? Should I add some resistors before? Bear in mind I am new to electronics.

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Bare in mind? I'm supposed to imagine you naked? No thanks!

In any case, there are two problems with the data sheet: the voltage is specified as 4.8-6.0, which is clearly not compatible with a 9-V battery. The fact that it worked when you tried it simply means that you "got lucky" in terms of operating outside the specs.

The second problem is that the current required is not specified at all. Given the torque specification (which is surprisingly high for such a small, cheap unit), the current required will probably be much higher than what a common 9-V battery can deliver. Depending on how much torque you actually need in your application, you're going to need a much better battery than that, along with some sort of regulator.

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  • \$\begingroup\$ Thanks for the answer. I don't want to fry my servos, that is why I am asking. I am afraid if I power them with a 9v they might overheat and break. Is that possible? Or is it current that could break them? \$\endgroup\$ – Pacha Jan 12 '17 at 15:25
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    \$\begingroup\$ The 9-V battery probably can't deliver enough current to fry the servo (part of "got lucky"), but a high-current supply at that voltage probably would fry them under heavy load. \$\endgroup\$ – Dave Tweed Jan 12 '17 at 15:34
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    \$\begingroup\$ SG-90 draws 0.75A peak. 4 servos would need 3A. Recommended battery is a 4 cell (4.8V) AA Nicad or NiMH pack. AA Alkalines might be OK if the servos are not heavily loaded. \$\endgroup\$ – Bruce Abbott Jan 12 '17 at 17:05
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Voltage divider circuits using resistors are good when you are trying to sense the voltage at a point. That's the reason you are getting a 5V output. In reality, when you connect any load across the lower resistance, the equivalent resistance of the lower branch is the parallel sum of the resistor and the motors internal resistance. At this point, the output voltage to the motor will not be necessarily 5V. Try measuring voltage when your servos are actually drawing current while in motion.

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