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Hello,
I'm about to start a project that requires 2-3 servo's
I was wondering what the best method is to power them?
I would like to power is from a secondary USB plug, is that possible?
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You should use an external power supply, and allocate about 1 amp per servo (if they are standard sized hobby servos - 1/4 scale or other such large servos are going to need much more). This rules out using a "secondary USB plug".
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This is the servo I purchased
http://www.hobbypartz.com/43gexidised1.html

With my testing, I've gotten one servo to run off of the 5v power from the arduino, would it be possible to power only the second servo from another USB port?
« Last Edit: February 17, 2011, 09:25:31 am by JustXtreme » Logged

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My Geocrawler (A robot originally built on the VEX Robotics platform) uses a pair of constant rotation servos for moving the tracks.. I tried using the +5V from the Arduino, but the 5V regulator couldn't handle the load. I finally opted to direct wire the +V (center pins) of the servos from a 2ndary power source. (in this case, the 7.2V RC battery.)  The signal wire can be driven directly from the Arduino without any problems, but the servos need to be a little more 'Umph!"  As cr0sh said, they need to be at least 1-amp per servo.. and using the USB port might not do it, or worse, you could burn-out the internal fuse to the port if the servo draws too much.  Most servos run between 5V to 8V. (Not sure I would try the 9.6V RC battery.. might be a little high. Not worth risking the electronics of the servo.)

Hope this helps!
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My Geocrawler (A robot originally built on the VEX Robotics platform) uses a pair of constant rotation servos for moving the tracks.. I tried using the +5V from the Arduino, but the 5V regulator couldn't handle the load. I finally opted to direct wire the +V (center pins) of the servos from a 2ndary power source. (in this case, the 7.2V RC battery.)  The signal wire can be driven directly from the Arduino without any problems, but the servos need to be a little more 'Umph!"  As cr0sh said, they need to be at least 1-amp per servo.. and using the USB port might not do it, or worse, you could burn-out the internal fuse to the port if the servo draws too much.  Most servos run between 5V to 8V. (Not sure I would try the 9.6V RC battery.. might be a little high. Not worth risking the electronics of the servo.)

Hope this helps!

Normally, most regular servos (that I know of) can be driven with 4.5-6.0 VDC - so at 7.2 VDC, you may be overdriving them (unless you are using servos which can handle that voltage?); at 9.6 VDC, that would be waaay overdriving them...
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I have a robot with 18 servos. I use two 8 amp BECs and a 3 cell LiPo battery. The BEC is used in RC models to reduce the 11.1 volts of the LiPo to 5 or 6 volts to run the servos.
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@dbiltcliffe can you tell us the manufacturer / supplier / model of the BECs?  I'd like to try these for something similar....
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I am using the TURNIGY 8-15A UBEC for Lipoly. You can find it here http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6233 or on ebay.
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