Wall Wart Power

As I described in an earlier post, I've decided to use external power with my motor shield to drive my servo motors. The question that left was what exactly I should use as that external power source. Unfortunately, the servos require 5v power, which essentially rules out batteries as an option. AA, AAA, C and D batteries are only 1.5v, which is far too little, and 9v batteries, which might feasibly work voltage-wise, have far too little capacity to drive the motors for any length of time whatsoever. Any larger batteries will have both too much voltage and way, way, way too much weight. The best option would probably be to order a 5v battery online, but that would be both expensive and time-consuming and, for all I know, ultimately unsuccessful, so instead I plan to use a 5v wall wart from some phone long ago lost to the ages.

While electronics draw only what power they need from batteries, wall warts function differently, and will feed the full amount of voltage to the components regardless of the actual power needing to be drawn. This is an issue because although the wall wart I'm re-purposing is rated for 5.1v, the load on the wall wart in amps was likely to be different than the load the phone required. If the load were less, the wall wart would feed more than 5v to my engines and possibly destroy them in the process. To make sure this wouldn't happen, I cut off the end of the wall wart cord that would have plugged into the phone, stripped the positive and negative wire inside, and tested the voltage passing through them with no load using a multimeter. To my surprise, the multimeter indicated that the wall wart was still providing almost exactly 5.1v of power. As a result, I've decided to go ahead and try it with the servo motors, as the worst that can happen is that the load from the motors will be too great for the wall wart to provide enough power to run them. That'll keep my motors from running, but at least it won't damage them, and I can then get another wall wart and test that, hopefully with better results.

Below are a couple images of the wall wart I plan to use: