Using multiple 3A SMPS for more current to power servos

Hi there,

I'm about to build my first robot artm - a design of my own based loosely on the Uarm.

It will be 5 DOF using ubiquitous cheapo servos (4x MG-995 1x MG90 micro).

I've seen the stall current of the MG-995 is quoted as 1500mA and the MG90 as 700mA so I think a power supply capable of 7A @6v will be required.

I'm aware I can mod a PC PSU to get 5v but want to use 6v for max servo strength.

I've seen the common 3A SMPS boards in packs of 5. They have variable output voltages - one even said it could handle 10A "with cooling".

Would it simply be a case of running 2 or 3 of these in paralell to get 6 or 9A of current - or will I need supporting components?

I propose running the 3A SMPS' from either a 240v connected 12v 10A SMPS, or a 12v leisure battery.

Grateful for any guidance you have


Probably not a good idea. One SMPS will have a fractionally higher voltage than the others. Maybe 0.01V That one will supply all of the current and the others don't contribute because the output voltage is still above their threshold.

In practice it's not going to be this bad. The high one will sag a little and the others will contribute. However it's not a reliable system. Buy one power supply of the appropriate rating. Give it the cooling it needs.

You might consider getting a UBEC like below for each big servo and maybe share one between two smaller servos. They can be set for 6v output and are made to power servos.

You never connect voltage sources in parallel.

Just use one for each servo or pairs of servos.

A 3A SMPS will not run at 10A however much cooling because the inductor will
saturate and it will (hopefully) shutdown (or else burn out).