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Author Topic: Power standalone atmega328 and servo motor via 9V battery  (Read 2002 times)
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Athens, Greece
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Hello everyone,
i want to power the arduino chip (standalone- not on arduino board) which is 5V btw and a servo motor which needs 6V to operate (well it operates also at 4.8V but with less torque..)

I have a 9V battery, an 7805 regulator (9V to 5V) some 10uF caps and a potensiometer.

How do i do that?
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Valencia, Spain
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With only those components?

Your motor's going to be running at 5V...
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Athens, Greece
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ok, so what else do i need?
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Left Coast, CA (USA)
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Well before you dive into details, are you sure your 9 vdc battery can supply the current requirements for a servo? What kind of battery specifically are you working with? Small 9 volt batteries designed to power smoke alarms just don't work for servos that have motors in them.

Lefty
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Athens, Greece
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you mean that the 9V battery doesn't have the amperage to start the motor or that it will drain the battery quickly?
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Athens, Greece
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would you suggest 4 AA batteries instead?
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would you suggest 4 AA batteries instead?

Yes, that will cost you a lot less in batteries.
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ok how about power? 4 AA's are more powerful than a 9V through a regulator?
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Four AA batteries won't work with your 7805 because you'll need at least 7 volts input (look up your specific 7805's data sheet for specifics). I use 6 AA batteries for input. A 7805 and a 6V regulator in parallel from your 6AA batteries would probably work ok. Don't forget to decouple. http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
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If you are going to more than ~8v power supply, then you could make a setup like below to supply 5v to the chip and 5.7v to the servo. If you use a 6v power source, a diode in the supply to the chip would reduce the voltage to ~5.3v.

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As your servo need 6V, the obvious solution is 4 AA alkaline cells, feeding the servo directly, and feeding the atmega328p through a silicon diode.
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ok got it! thanks everyone!

but, cost aside, which is more preferable, to drive the motor with 4 AA's or with a regulated 9V battery.

i've read somewhere that 4 AA have more amperage than a single 9V (regulated to 6V of course)
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but, cost aside, which is more preferable, to drive the motor with 4 AA's or with a regulated 9V battery.

i've read somewhere that 4 AA have more amperage than a single 9V (regulated to 6V of course)

You can find relevant information at http://data.energizer.com/.
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so, i decided to go for the 4 AA rechargeable batteries. 4*1.2=4.8V right?

WRONG!
these eneloops i bought give 5.67V, that means 1.4 each.

so the atmega328 can hold 5.5V. if i connect 5.67 will it burn? i mean for 0.17 Volts?
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so, i decided to go for the 4 AA rechargeable batteries. 4*1.2=4.8V right?

WRONG!
these eneloops i bought give 5.67V, that means 1.4 each.

so the atmega328 can hold 5.5V. if i connect 5.67 will it burn? i mean for 0.17 Volts?

6V is the MAXIMUM voltage so you should be ok, but I would just toss in a series diode to drop the voltage a little more.
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