Electronics > Electronics

One battery or two?

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Soeren:
Hi,


--- Quote from: ErikY on December 10, 2012, 03:15:51 PM ---I want to run 12Volts to the servos, to give them the power they need.

My question is, should I run the same 12 volts through a 5V regulator for the ATmega328p, or should I use a second say 6Volt battery  for the Atmega?

--- End quote ---

Go with a single battery, using two is a poor substitute for doing it right and two batteries will never be fully discharged at the same time.

I'll suggest using a switch mode regulator, either one from Dimension Engineering that is a 3-pin drop-in replacement for the 7805 or, if you want to save some cash, make one yourself (either a switcher or, if the current demand on the 5V line is fairly even, a filtered chopper, perhaps followed by an LDO regulator).

If you use a linear regulator, you'll loose more than you use. Whether that is a problem depends on how much current you need on the 5V line of course.

To keep the two "sides" from influencing each other, just connect them both right at the battery terminals (both +12V and ground) and don't use thin wire - something like what's used on your mains wired lamps or heavier. The battery is the lowest impedance in the crcuit, so this wiring "pattern" will keep servo- and motor noise from spreading to the logics department via the wiring.

Gertlex:
I use both methods with Dynamixel servos.  The single battery approach is definitely nicer.  I use 3S LiPos with these regulators. I buy lots of these, as well as the 3 pin molex connectors to hook up my servos to... and other related hardware.

That said, I've only done the single-battery approach with a 3x AX-12 bot so far.  I'll have a 3x MX-28 + 2x AX-12 bot in a month or two though.  The double battery approach used a 3S LiPo and a 2S LiPo, since the Axon couldn't take a 3S directly (though I now know I could have just replaced the capacitor on the Axon.

ErikY:
Everyone,

Thanks a lot for the detailed information, very helpful!

I definitely would prefer to use 1 for obvious reasons.

I will take all of your information into consideration as I design my next augmented microcontroller.

Once I have the design done, I will post it up, and hopefully some of you guys can give me your thoughts.

Thanks!

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