Which Power Supply to run 5 servos simultaneously?

Other Hardware Motors, Mechanics, Power and CNC
1

I want to use 6 MG996R servos for a robotic arm. In my use, 5 servos may run simultaneously. But I’m confused with which power supply need to be used?
Stall current is 2.5-3A, so 3x5=15A total stall current and the operating voltage is 4.8-7.4V. So it is less voltage and more current issue. I’ll be using a PCA9685 to control my 6 servos.

If I use 12V 20A SMPS(available in my country), can I use a high current buck converter with it to reduce it to 6V ? Or, any other alternative or portable option would be suggested?

Kindly help me in this regard.

2

At startup, all six servos could draw stall current, so 6 servos x 3A = 18A.

3

That’s why I was thinking of using a 12V 20A SMPS but unsure if it is possible to step down using buck converter or any other cost-effective/portable alternatives are there?

4

Yes, buck it down to 6v but be careful using the PCA9685, I don't think the power traces will survive your loads, wire the power direct instead.

5

This will give you power problems. You can modify the module for additional current or supply the motor power separately which is what I would recommend. If you use a buck converter be sure it will supply enough power for the motors.

6

Thanks @sonofcy and @gilshultz. So I will connect the Red wires to the breadboard +ve rail connected with my power supply and the signal and grounds to the PCA9685 and esp32/arduino gnd. Am I right?

I haven’t work with so much servos before and so it bothers me if wrong supply may destroy them.

7

Care to explain about the 6th servo. Will it be powered off or set to the neutral position. If not in the neutral position, it will still draw power to hold the set position.

8

Make sure ALL grounds are connected together.
The breadboard +ve is either 5V or 3.3V depending on your MCU.
Signals to the PCA9685 plus gnds
Heavy wires from PSU to servos at 6V via buck converter. The 12V 20A PSU will be able to handle that.

9

The skinny conductors in cheap breadboards cannot handle currents like 18 Amps, maybe 1 ~ 1.5 for short periods (a second or two).

10

Personally, I would connect both positive and negative wires from the servo, directly to the power supply, and connect the power supply negative to the controller ground.

You need to have the controller sharing as little as possible conductors that have serious servo current flowing.
Something like this;

image
image1040×942 30.9 KB

Comment, criticism all welcome.

Tom.... :smiley: :+1: :coffee: :australia:

11

Thanks again @sonofcy , Thanks for ensuring @JCA34F , and @TomGeorge , that’s superb that you took time to draw a sketch, that’s truly helpful.

But I was wondering about one more thing, that the servo wires have connectors and the all 3 wires are connected together, also the PCA9685 has 3 close header pins to connect. How would I able to connect the +ve and signal separately? Do I need to cut them and connect?

And I have found another supply, 6V 4.5ah Sealed Lead-acid Rechargeable Battery. How would it be if I use it for 6 servos?

12

You need to make a wireing diagram.

In order to decide if that battery is sufficient, determine the maximum current draw of your project, if that number is less than the battery maximum then you are good to go. Also divide the capacity of 4.5ah by the average continuous draw to determine how long the battery will last.