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Author Topic: Enable more power in usb port  (Read 804 times)
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Hi, I'm using ATmega 2560 with a big servo. My computer block power in the usb after 2-3min of use. Do you know how to remove the power limit in usb port with windows 7 ?

Thanks
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That's not the right approach - the "big servo" is not a suitable load for USB power at all - power it from a separate supply
that can safely handle the peak currents (probably several amps).
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I've learned a cheap little transistor will do the trick!  Just make sure to read the datasheet for your servo, and the transistor you want to use, to make sure you are matching the transistor adequately to the application.  Then route your external power source through the transistor, and trigger it with an arduino pin!

Viola!

EDIT:  I don't have tons of experience with servos...  I have been working more with DC pumps, but this is what I do for them and it works great!  Since servos have 3 leads coming off them, maybe you can just power them directly from an external source?  That is a bit beyond me at the moment actually, and I didn't want to steer you wrong with my inexperience.  So, this is my disclaimer lol
« Last Edit: February 14, 2013, 10:06:49 am by Jim_Socks » Logged

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The external power supply I bought is only 1A, seems to be not enough for the servo.

Can you give me an example of electric plan with the transistor please ? thanks
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Sure!

Here is a little schematic I found using a transistor and a DC motor.  It uses a transistor that does not have it's own internal diode, which is why it is in the schematic.  This is the same way I started wiring my pumps before I bought transistor arrays (chips with 8 transistors + diodes)

Be sure to check the datasheet of your transistor, because your emitter and collector may be on opposite leads as this schematic, and it may even have it's own diode.

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If you can, search online for the specs of your servo.  Find out it's electrical specs under load/from stall, then return the power supply you bought and use the money to grab a power supply that matches the values you saw on the spec sheet.

EDIT:  I find it ironic that I am posting servo motor advice for you here, while simultaneously having a post right next to yours looking for folks with servo motor experience to help answer questions I have.  LOL.  As such, please take my experience level into consideration when following my servo motor advice- I would hate to hear I steered you wrong!
« Last Edit: February 14, 2013, 10:28:01 am by Jim_Socks » Logged

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The servo is MG996R High Speed Digital Metal Gear. They don't specify the amps, only volts... I can't find a 9V 2A power supply ?
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The servo is MG996R High Speed Digital Metal Gear. They don't specify the amps, only volts... I can't find a 9V 2A power supply ?

Here you go: http://www.ebay.com/itm/9V-3A-AC-DC-Power-Supply-Replacement-Adapter-with-2-5mm-x-5-5mm-Tip-Center-/190707750291?pt=LH_DefaultDomain_0&hash=item2c67115593
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I can't see your link, so does this one will works?

http://www.ebay.ca/itm/NEW-9V-3000mA-3A-AC-DC-Power-ac-adapter-Power-supply-/390121832757?pt=LH_DefaultDomain_0&hash=item5ad512c135
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Is it 5.5mmX2.5mm plug for a ATmega 2560 board ?
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"will it work" will depend on a lot more than just the supply. However, you mentioned you were looking for a 9 2A power supply (which I linked to). The one you linked to is a 9V 3A power supply. They will both work the same, with the difference being that the one you linked to can source more current.

Basically if you wanted to draw about 2A of current, using a 3A supply would be safer.
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You could try this idea (modified from a Silicon Chip design):

note: You can't really escape the limitation of the PTC fuse on the board though but you do apply power at the same time this way.



* SwitchedSupply.JPG (52.54 KB, 685x457 - viewed 36 times.)
« Last Edit: February 14, 2013, 01:12:50 pm by pwillard » Logged

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Am I the only one thinking that all the people responding here are not aware of that OP is using a Hobby servo ? e.g. two pins for power and one with a PWM signal for position. A transistor or whatever won't do a damn thing!

OP: Get a 6V 2A power supply for supplying the servo.

// Per.
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