Small servos and power

My apologies for what is no doubt a very silly question, but I’m quite new to all this.

I’ve got a Mini Maestro 12 Channel Servo Controller, three Hitec HS-85BB+ servos ( … micro.html) and a couple of RBG LEDs. I’ve got the board turning the LEDs on and off like a champ, but I’ve yet to have much luck with powering the servos.

The board is going to be permanently attached to a computer and controlled over USB in a long term installation so I’d rather not use a battery if possible and mains power scares me a little. The servos are operate in the 4.8-6v range and they’re not going to be lifting anything heavy - can the board power them directly? If not, perhaps an old mobile phone charger or stripped USB cable as in this thread - MicroMaestro USB conntected & servos power from another USB ?

Thanks in advance.


Please read the “Mini Maestro Pinout and Components” section of the Maestro user’s guide because it explains how to power the Maestro.

Also, please see the Maestro FAQ entitled “Can I power my servos with the USB port?” in the Resources tab:

If you really want to power your servos from USB, you could add a wire from the Maestro’s +5V line to the positive servo power rail, but this is not recommended. An old mobile phone charger would probably work too.


Yep, I read the manual, saw the picture of the wire attached to the bottom of the Micro Maestro and have read the FAQ too. I was just unsure of whether the advice applied to the specific servos I have which as far as I can tell are rather low power affairs.

I suppose the answer is “it depends”.

Thanks for your response.

“Low power” is relative. The specifications for the HS-85BB+ are 8mA/idle and 240mA no load operating at 4.8 V. This means that any time any servo moves, it will require AT LEAST 240 mA. As the servo arm begins to move, there is a transient startup current draw that is much higher. If three move at once, that requires 720 mA. If a load is attached to any servo, even more current is required.

No more than 500 mA can be drawn from a USB port, with 100 mA being the default limit, so an external power supply capable of supplying at least 1 ampere (preferably more than 2 A) at 5 to 6V is required for your project.