need 6.5v and 9v from a battery. whats the best way?

[dequo]

I need to run an arduino at 7-12v, and two servos at 6.5v from a single battery.

i will probably be using a battery made for remote control cars at around 7v

the arduino will only use about 20mA but the servos will use up to 0.6A each

i have been looking at traco voltage regulators http://www.tracopower.com/General-Purpose.215.0.html  but i was hoping there was a cheaper and simpler way?

[Simon]

why do you need 12V for the arduino ? look like you can power the lot from 7V I can't see 7V doing a lot of harm to the servos but you can always put a diode in series with them

[dequo]

i need the voltages to remain constant over the life of the battery charge. this is for a university project, i dont think they would appreciate me disregarding the servos rated voltage

[saturation]

A cheap and simple way is use 2 battery packs, one for 7-12, another for 6.5.  It not elegant but its fast and cheap.

You make your own battery pack out of 1.2V NiMH x 10, the top of the pack is 12V and tap at the 5 -6 cells for lower voltage.

If you need stricter voltage regulation you'll need a voltage regulator for each, as needed. 

if you need compact elegance, then a single battery pack supply with a regulator feeding each of your demands, but if you don't need that yet, why go there and spend more, unless its part of the class exercise.

[Simon]

well I suggest using a higher voltage battery and a couple of buck SMPS's say 12-14 V, if your battery is 7V nominal and you want guaranteed 6.5 constantly, 7V is to close for most regs and it will soon fall to near 6.5V, so you need to start higher to ensure you always have enough voltage to make the most of the battery

[alm]

There are some LDO regulator with very low drop-out voltages, they use a MOSFET pass element. But I don't think they will handle 12V input voltage, most top out at 5.5-6V.

How about a buck or buck-boost converter to 9V and an LDO for 6.5V? Or a separate buck converter for 6.5V if the servo's draw lots of current. There are some easy to use switchers (eg. National Simple Switcher series) that need almost as few external components as a linear regulator, the only extra component is an inductor, and sometimes a diode.

[Simon]

the big question here being is a higher voltage battery allowed ? if it is it makes life easier and more efficient

[dequo]

thanks guys ill read into this stuff in the morning. and yeah the battery has not been chosen yet so it could be any voltage really