next topic »

[on:]

I want to power either the ardweeny (http://www.solarbotics.com/products/kardw/resources/) or the RRRRRRRRBBA (http://www.instructables.com/id/The-RRRRRRRRRRBA-or-What-They-Dont-Teach-You-in-/) by battery.  Can I stick a 6V battery onto their of these? ....or do I need to have a voltage regulator?

[Reply #1 on:]

Hello nycthinker,

None of these boards has a voltage regulator. So I'd bet you need one if you want to connect it to a 6v battery.

Maybe you can try a not so "bare bones" arduino, like this: http://itp.nyu.edu/physcomp/Tutorials/ArduinoBreadboard

Eduardo

[Reply #2 on:]

Quick and dirty : 3 AA Alkalines gives ~ 4.5 V. Close enough to 5V with no regulator.

[Reply #3 on:]

The problem is that if supplied some Arduino boards with less than 7V, the 5V pin may supply less than five volts and the board may be unstable, right?

Eduardo

[Reply #4 on:]

The intention was to feed the 4.5 V directly to the 5V & Gnd.  The regulator doesn't get a look in.  4.5V is close enough not to give any problems unless you have some particularly sensitive external circuitry.

[Reply #5 on:]

Thanks for the suggestions.

I am currently using a RBBB running off of a 9V battery which works great, but is still too bulky.  Ideally, I'm shooting for the fewest number of parts and the smallest battery possible.

[Reply #6 on:]

4 NiMH cells in series would give you about 5V,  which should be "close enough" even after the voltage sags a little as the batteries are discharged.

BUT you should read the cautions all over the board about likely problems if you're going to putting this in a robot or other device with motor(s).  The electrical noise from motors or solenoids can really screw things up.

[Reply #7 on:]

If your paramount objective is power saving, then using a voltage regulator will worsen things because it will suck energy while cutting the extra voltage (and it won't either augment voltage when battery are low, obiously).
If you look at the specs here:
http://www.atmel.com/dyn/resources/prod_documents/doc8161.pdf

you'll find this meaningful diagram that shows how the 328 can be run from 1.8V to 5.5V:

In order to decide if your project can cope with low voltages, you'll have to consider these facts

Pros
- running at a lower voltage will draw much less and extend battery life (running at 3V instead of 5V means kind of 3x improvement) .

Cons
- analog inputs will use supply voltage as reference
- all outputs can't go over the power supply voltage
- you have to run slower, ex: 2.7V=8mhz and you have to consider battery voltage decreasing with time (alkaline voltage drop is very steep, nimh and lithium are better) anything in the range 3V-5V might be reasonable.
- clock frequency won't be precise, consequently all time related functions as well.
(the latter two points might need code compensation)
- peripherals will get at max power supply voltage.

If your project can manage the cons you'll have a larger choice of battery options.