C3 on USB power + servo?

prof_braino

I have a tiny $4 servo that I wait to test.

I was going to hook it to the C3, but the C3 cannot use external power when USB is connected.

So my question: Will commanding a servo with no load on it to various positions draw more than 500 mA?

Martin_H

I wouldn't think so, but measuring the servo's current consumption with a DMM is the only way to know for sure.

Lately I've been using separate power supplies (which share a ground) for my Propeller and servos. That way the propeller only supplies a small amount of current to the signal line, and the battery supplies the bulk of the servo's current. I did this because servo noise was resetting my propeller chip, but it might be a way for you to avoid drawing too much current from your USB port.

schill

Here are a couple related posts.

C3 with USB connected and external power:
http://forums.parallax.com/showthread.php?128699-C3-power-and-USB-usage

I think there is at least one more thread about this somewhere.

Supplying servos connected to C3 with their own power (not 3.3v or 5v from C3):
http://forums.parallax.com/showthread.php?128724-C3-tri-ports-headers-%28servo-ports%29-and-power

Sapieha

Hi prof_braino.

Can You don't use Split cable that use 2 PC-USB ports as some HD's to give You 1A

prof_braino wrote: »

I have a tiny $4 servo that I wait to test.

I was going to hook it to the C3, but the C3 cannot use external power when USB is connected.

So my question: Will commanding a servo with no load on it to various positions draw more than 500 mA?