How do I configure power supply for robot arm?

Other Hardware Motors, Mechanics, Power and CNC
1

This is a 2-part question. Part 1 is how to calculate how much power is needed. Part 2 is how to supply that power.

PART ONE

How can I calculate the power required for any configuration of servo motors? For example, here are the specs for MG996R:

  • Operating Voltage: 4.8 to 6.6V
  • Max rotational speed: 0.15 seconds to turn 60 degrees (No Load @ 6.0V)
  • Running Current 500mA - 900mA @ 6V
  • Stall Current 2.5A @ 6V
  • Stall Torque: 11 kg/cm @ 6V
  • Stall Torque: 9.4 kg/cm @ 4.8V

Project

I’m building a robot arm that requires 4 MG996R motors, 4 10k ohm potentiometers, and an Arduino Nano clone (CH341SER) that maxes out at 5 volts.

PART TWO

Cordless power supply

What would be the recommended cordless power supply for the configuration above? Battery pack?

2

Well the worst case is that all 4 of those motors need that current at the same time, so there's 10A. Add some margin so say 15A? The current through the pots and for running the Nano are pretty insignificant compared to that.

1 Like
3

My project doesn’t need to power the servos at the same time. The potentiometers only use up around 0.3 watts. For the battery pack, the best option right now is a 6V lithium-ion battery.

What do you think and should operating voltage and running current be considered?

I apologize for not answering quickly, I have been researching power supplies.

4

It doesn't matter. The power supply has to be capable of supplying the start/stall current for all four servos, all the time. That means you need a 5-6V power supply capable of at least 10A, as noted above.

5

That is the same as saying you don't care what position the servo is. Seems strange for a robot mechanism.

6

I'm putting the robot arm on top of a car chassis that has 2 gear motors, here are it’s specs:

  • Shaft length: 7 mm
  • Shaft Diameter: 5.5 mm
  • Size: 55 x 48 x 23 mm.
  • Operating Voltage: 3 to 12V.
  • Current (without loading): 40-180mA.
  • RPM: 100 rpm.
  • Output Torque: 1 kg-cm

The kit comes with a battery holder that can hold 4 AA batteries. I’ll need to power the 4 MG996R motors and the 2 gear motors. Since it doesn’t include the stall current in the specs, i’m not so sure what to get.

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