CR Servos and power supply

I am going to be using a Micro Maestro controller to run two to four SpringRC SM-S4303R Continuous Rotation Servos.
I would like to power it from a wall plug so I was wondering which voltage adapter to get. It looks like the servos are rated at 4.8 to 6 volts, so would anything over 5 volts be overkill, or could I use a 9 or 12 volt adapter? I thought an amperage rating of 3 to 5 amps for the adapter would be sufficient.
I have read the blog posts on servos and as good as they are I’m still something of an electrical dunce, so any advice would be greatly appreciated.

What is the power rating for each of the servos? You need to get a power supply that is rated at least four times the power draw (amperes) of the servos if you’re going to power four servos. Note that it’s the max power draw (stall) that matters, not idle draw (that you will measure when the servo is just sitting there.) 3A sounds like too little to me.

If the servos are rated 4-6V, then you should get a 5V or 6V regulated power supply. If you get a higher voltage, then you will likely burn out the servos. You could also get a 9V or 12V power supply, and then get a power converter (or UBEC) that takes the voltage down to 5V or 6V, if you make sure the UBEC/converter is rated for the necessary amperage. I think 8A would be a reasonable rating for both an UBEC and a power supply.

Thanks jwatte.
I don’t know what the current draw is for the servos. It’s not listed in the specifications, so I guess I’ll have to find a way to measure that. Pololu does have a 5v 5 amp adapter that might work.


Generally, you should plan for about 1A of current capacity per standard servo in your setup. The 5VDC 5A AC to DC adapter you referenced will probably be fine for those four SpringRC SM-S4303R Continuous Rotation Servos.



I was recently testing one of the SpringRC continuous rotation servos and the stall current was right around 1A when running at 6.0V, so I agree with Derrill that a 5VDC 5A wall adapter should be fine for you.

  • Grant

Thank you all for the information. The 5VDC 5A is what I’ll use. Thanks again.