Simple stand-alone power supply for an arduino device?

Question

The world of diy electronics is pretty new to me, but I have a sparkfun kit, a temperature sensor, and a new greenhouse that I want to learn the behavior of. Basically, I want to record the temperature once an hour. I'm happy saving that locally and periodically connecting the thing to my computer to download the data, but I don't know how to power this contraption. There's no power source near the greenhouse, so I think my choices are batteries or maybe a solar panel.

A quick look at the battery page of sparkfun reminds me that I know nothing about this. How long would a 3v battery last? A 8v? A Lithium Ion battery? How does something like that get recharged? Can these be plugged directly into the board somehow, or (more likely) is there an intermediate step? And what would that be exactly?

Is it too much to hope that there exists somewhere a simple recipe to follow to supply an arduino with a stand-alone power supply? I'm open to all options, with preference toward the simpler options (at least to start with).

Answer 1

Here is a possible DIY solution for solar powered Arduino system: https://www.cooking-hacks.com/documentation/tutorials/arduino-solar/

The principle is pretty basic. A rechargable battery sufficient to power the system for 18-24 hours, a panel of photo-voltaic cells (solar battery), and something to manage charging the battery from the solar panel.

There are many possible solutions, from full custom assembled from various parts, to a turn-key complete system in a box. It would be good to have a basic meter if you are playing around with electronic stuff. You could measure the actual current used by your Arduino, and calculate the size of battery you need for the expected solar radiation in your location. You would need a larger battery farther toward the polar regions than you would need near the equator, etc.

Answer 2

Once you know the voltage (5v) you can calculate how long the battery will last based off it's amp-hour rating (Ah). For example, the battery you posted is only 110mAh. That's tiny. It would only supply 110 ma for an hour.

Connect your Arduino project to an ammeter and measure the current draw. From this value you determine what Ah rated battery you need. For example: you find the arduino draws 20 ma (typical for Arduino). If you want that to last for 10 hours, you'll need a 2000 mAh battery.

Since Arduino powers off a micro-USB there are several little solar battery packs that could fit the bill, but it's not likely that they are waterproof. Here's an example of a battery pack combined with solar. Keep in mind, you're powering off the battery, NOT the solar panel. A solar panel alone will not provide the proper voltage and be stable!