MicroMaestro USB conntected & servos power from another USB

I’ve just received a Micro Maestro 6-channel USB and I want to power it from PC USB port.
My question is : may I connect the servos power to another USB port coming from the same PC ?
I’m going to use three servos that can work from 4.8 to 6 volts, draining from 285mA to 500mA each
(no one of the servos will have to work while another one is working anyway…)
And is it safe to install the Micro Maestro drivers having all the servos already connected to it ?

I have found some hints about what I’m asking on this forum, but I was not able to find posts answering to my question
so precisely, that’s why I’m posting this.

Thank you so much for any help coming out ! :wink:

Hello, turbolenta.

The answer to this depends on the properties of your other USB port and doesn’t have much to do with the Maestro. If your other USB port is capable of supplying 500 mA even when there is no valid device plugged in to it, then it could work. In general we don’t recommend powering servos from USB, but it could work for you.

It’s OK to do that, but I wouldn’t recommend it. Instead I recommend getting the USB drivers installed and connecting the Maestro to your computer first, before attaching any other electronics to the Maestro, so that if something goes wrong later we will at least know that it was working at some point, which helps narrow down the problem.

Good luck on your project!

–David

Thank you so much for answering me so quickly and clearly !

Hi! I’m actually trying to do this exact same thing with my servo/controller, and I was wondering, what sort of cable are you using to connect the power pins to your USB port?

I’m using a usb cable: as you cut it, you’ll find there are 4 wires : one green, one white, one black and a red one. Insulate the green and the white ones (as you’re not going to use them). Now you can connect the black to the negative pin of your Micro Maestro servo power and the red to its positive. You should have a USB plug at the other end of that same USB cable, right ? So now you can plug it to a PC USB slot… I’m going to test it myself within this week end… I would suggest you to wait for my own experience first… and remember that a USB slot provides 5 Volts at 1 Amp, so you should check your servos current drain before setting up all this stuff.

You should also take into account powering your servos using the right batteries as Pololu staff suggest, as I’m not responsible for any damage coming out from your set up.

Good work, anyway !

Awesome, please do let me now it works out for you.

Also, shouldn’t you really attach the green USB wire as well? That’s the ground, and seeing as this is an improvised mechanism, it’d really be best to have one, I would think…the screw-hole in the middle of the board at the top seems a likely candidate for attachment points.

I tested my set up this morning. No green wire connected, only the positive wire (red) and the negative (black) connected to the board servo power pins, and it worked fine !
I don’t know what is the green wire for… but if you’re looking for a ground connection just for discharging electrostatic current, you could seal the board inside a plastic box with all its wires connections coming out… that’s the way I did it.

Anyway, you can take a look at my set up and my servos current drain at the top of the page… if you want to have a try… it’s up to you ! Do it at your own risk…
but on top of that… have fun !!!

The green and white wires are differential data lines, so they are certainly not needed. You can learn more if you just search for “green” in the USB 2.0 spec:
usb.org/developers/docs/

–David

It’s working beautifully :smiley: thank you all for your information and help!

[quote=“turbolenta”]I tested my set up this morning. No green wire connected, only the positive wire (red) and the negative (black) connected to the board servo power pins, and it worked fine !
I don’t know what is the green wire for… but if you’re looking for a ground connection just for discharging electrostatic current, you could seal the board inside a plastic box with all its wires connections coming out… that’s the way I did it.

Anyway, you can take a look at my set up and my servos current drain at the top of the page… if you want to have a try… it’s up to you ! Do it at your own risk…
but on top of that… have fun !!![/quote]

Apologize for bringing an old topic back, but…

This is pretty much the only post I could find regarding this question, and I wanted to post that I, too, have had luck powering 2 HS-425BB servos (4.8-6.0V range, 150mA operating current at 5V) via a separate USB connection (red/black wires) installed into a ServoCity pan/tilt camera base (DD155/DDT500). The power cable works both in a Windows laptop and a standalone mini-ITX Linux PC. Yes, I can drive both servos at the same time under load.

I am planning to try tapping for power into the same cable that connects to the Maestro, but it will be difficult as the leads are very tiny.