Go Down

Topic: How are people powering battery-driven projects? (Read 1 time) previous topic - next topic

retrolefty



It's a quandary...a 4-cell AA battery is too high voltage for the 5v input, but almost too low for the 78M05 regulator input, adn will drop out fairly quickly despite battery capacity left.  A 9v doesn;t have the endurance of multiple batteries. 
I do see however there is a 5v switching arrangement on the Nano at least, to switch, from the USB 5v to the 5v main bus?  Not sure that is an alternative...

So what are people doing in this regard?


So nobody can blame me, I won't suggest that anyone do this, but *I* personally have run an Uno R3 board on 4 AA lithium cells in series. As you may or may not know, a brand new lithium AA cell is around 1.80 volts DC, which is 7.2 volts for 4 of them.

The 4 AA cells in series power the board's "5 volt" supply directly. It does not go through the regulator.

I've made several projects powered like this and they are running fine.




Well that is well above the absolute maximum Vcc voltage limit of 6.0 per the AVR datasheet. How do you account for not having a bunch of burned out boards? And it's magic is not a proper answer.  ;)

Lefty

cornwallav8r

Krupski... I kinda expected that answer :-)
Yeah, it doesn't surprise me that it'll work over spec.
But the important thing here, is I want to make a whole bunch of these...and they need to work on every single item, not just "that one I tried on the bench".  Not surprised at all it'll work for awhile like that in testing.

giantsfan3

@liudr:
Just curious: What would be some DISadvantages of switched-mode dc-dc converters? Aside from cost, it appears they are better than LDOs in most situations, am I wrong?
E.g., I am considering powering my circuit with a Li-ion battery and using the TPS63000/TPS63002 Buck-boost regulators; they seem to have very good efficiency in both buck and boost modes.

CrossRoads

I've run uCs off 3 AA batteries, ~4.5V, even a '2560 based board @ 16 MHz.

I've also run 3.3V Promini @ 8 MHz from a single LiPo battery.

I don' think I saw what the application is here. Haven't seen what the need is for boost converters unless the goal is to run from  a single AAA or AA size battery.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

mauried

The single biggest issue with battery projects is how long do you want the batteries to last
before they have to be replaced.
That effectively defines what sort of batteries are needed, and hence what voltage batteries are needed.
Id stay away from any kind of arranagement that needs voltage converters of any kind, because although they are more
efficent that linear regulators, at very low power levels , they can consume more power than the micro.

Go Up