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Author Topic: How much current can an Arduino board supply?  (Read 1872 times)
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I want to power and Iteaduino board from a 12V battery.

I want the board to charge my Android phone (300mA), as well as power a Hitec HS-5485HB servo (Standard size, digital, 400mA@4.8V no load) and a Hitec HS-485HB (Standard size, analog, 150mA@4.8V no load)

Can the board do this on its own?
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Nope. Regulator is only good for 800mA, and from 12V source it will get Real hot with that much current and likely go into thermal shutdown.
Better to split the 12V supplly line and add a 2nd regulator.
Even better, use a switching regulator to bring the 12V down to 5V for the phone & servo and the other part, get away from just blowing all the 12V power as  heat.
Examples:
http://www.pololu.com/catalog/product/2110
http://www.digikey.com/product-detail/en/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781
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No, certainly not a servo (bad practice to share supply between microcontroller and an inductive load anyway)

The on-board regulator will have to drop 7V, and can't dissipate much power.  300mA @ 7V is 2.1W, much too high, it'll overheat and shoud shut down.  Think about an external 7805 with decent heatsinking.
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I thought the Iteaduino has a DC/DC converter, not a regulator, and that it takes the supply voltage down to 5V. That's why I was looking at it. I thought that should take care of the heat issue?

That question aside, I heed your comments about running servos off a board. I see lots of people doing it and am wondering whether it is more a prototype to prove it *can* be done rather than whether it *should* be done. This thing is going to be outside 24x7 and located miles away from people. It needs to be rock solid. Oh, and the whole thing is going to be solar powered as well.

I have to have the phone running off the Arduino board because it is going to be driving the board in USB host mode, but it needs to be charged be the board at the same time.
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I thought the Iteaduino has a DC/DC converter, not a regulator, and that it takes the supply voltage down to 5V. That's why I was looking at it. I thought that should take care of the heat issue?

It does seem to have a switching regulator, so that is a good thing, lot less heat generated for a given voltage drop Vs linear regulators. However a servo should still use it's own voltage source good for at least one amp per servo.

That question aside, I heed your comments about running servos off a board. I see lots of people doing it and am wondering whether it is more a prototype to prove it *can* be done rather than whether it *should* be done. This thing is going to be outside 24x7 and located miles away from people. It needs to be rock solid. Oh, and the whole thing is going to be solar powered as well.

I have to have the phone running off the Arduino board because it is going to be driving the board in USB host mode, but it needs to be charged be the board at the same time.
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