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I am building a robotic arm with 5 * SG90 9g micro servos to flex each finger and one MG996R servo as an elbow joint.

The servos were working inconsistently, with not enough torque and jittering a lot. After doing some research i soon realised that using the 5v supply form the raspberry pi was a terrible idea.

I've tried looking for ways to externally power the servos but i've just ended up more confused than i was before.

I like the idea of using AA battery packs rather than an external wall adapter.

The question is: How many batteries would i need to power all servos (possibly simultaneously)? Maybe a few 4*AA packs in parallel?

SG90 9g Micro Servo: Operating voltage = 4.8v

MG996R Servo: Operating voltage = 4.8v - 7.2v

Any help is appreciated.

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  • \$\begingroup\$ Try connecting them to the same power source as the raspberry pi, instead of through the raspberry pi? \$\endgroup\$
    – user253751
    Jun 18, 2020 at 13:21
  • \$\begingroup\$ I can't really do that because the way i power my raspberry pi at the moment is through a micro usb to my laptop. Maybe the batteries solution could also power the raspberry pi? That way i wouldn't need the micro usb cable. \$\endgroup\$
    – beatriz
    Jun 18, 2020 at 18:32

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The MG996R draws 2.5 A at 6 V. SG90's draw about 0.75 A peak each, for a total of up to 3.75 A peak for 5 servos. Therefore you need a battery that can deliver ~6 A.

A 4 cell (4.8 V) AA Eneloop pack would probably do it, but 2 packs in parallel would be better. If you use individual cells in battery holders the springs will drop more voltage than the welded joints in an R/C receiver pack, and then you will definitely need two 'packs'. Another option might be one 4.8 V pack for the SG90's, and another 6 V pack for the MG996R.

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  • \$\begingroup\$ Thanks! That's really useful. \$\endgroup\$
    – beatriz
    Jun 19, 2020 at 11:11

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