AA power!!!

Hi all,

I have a Duemilanove/Atmega328 I’m looking to use in a high-altitude ballooning project. I’m faily new to hardware, but after frying a few circuits in the past I already know my major weakness is power. Due to temperature constraints, I’ll be using some Lithium AA batteries @1.5V to power all devices, but the number of AAs is an open question. Any excess power converted to heat with my heatsink is a good thing, as long as it doesn’t fry anything.
Devices:

  1. my arduino :smiley:
  2. OneWire temp sensor (3-5V, <=18mA)
  3. Lassen IQ GPS module (3.3V, 27mA) with antenna
  4. SD card writer (via SDuFat), (3.3V, ampage unknown)
  5. SMS texting on a Motorola C168i via SSerial2Mobile - I don’t think I need any power for this as it survived in my freezer for a few hours without being used. But once I have everything assembled, if it needs more juice to send texts occasionally, this potentially could need power as well

Do you have any suggestions for the number of AAs I should use?
Also, all of my devices use 3.3V. Does the 3V3 socket on my arduino support all of this? Or should I use the 5V socket plus some heat? Or power them directly (plus some heat)?

I’ll be using some Lithium AA batteries @1.5V to power all devices

Be aware that the “1.5V” lithium cells actually put out closer to 1.9V when brand new. So the (somewhat common) practice of using 3 cells in series with no regulation (nominal 4.5V with normal batteries) can put out well over the max rated voltage of most micros… (it sounds like you’re planning on using the regulator, so you shouldn’t have a problem.)

You can use 3 AAs to power the duemilanove via the 5v pin. The 3.3V is created by the FTDI chip, is only spec’ed for 50mA, so you might be on edge there.
You might be better off using something like this to create the 3.3V efficiently to ensure you have enough current without frying the FTDI chip.

Or maybe use 4 AAs for capacity, and 2 stepdown regulators.

Or 1AA and 2 boost regulators, one for 3.3V & 1 for 5V.

Or use an 8 MHz/3.3V Promini

and 1 boost regulator

for minimal electronics size & weight.

Many options exist.